The reticular formation is a network of neurons located in the brainstem that serves several important functions. It is involved in regulating states of consciousness like sleep and wakefulness via the ascending reticular activating system. The reticular formation also controls posture and balance through reticulospinal tracts that project to motor neurons in the spinal cord. It is comprised of several nuclei that contain different neurotransmitters and integrate sensory information from various modalities to coordinate motor functions. Lesions in specific areas of the reticular formation can impact muscle tone and result in conditions like decorticate posturing.
The limbic system is a set of brain structures located deep in the brain that are involved in emotion, behavior, motivation, long-term memory, and olfaction. It includes the hippocampus, amygdala, and surrounding cortical areas. The hippocampus plays a key role in memory formation and storage. The amygdala is involved in emotional responses and regulating autonomic functions. Damage to limbic structures like the hippocampus and amygdala can result in conditions like Kluver-Bucy syndrome, anxiety, schizophrenia, and memory disorders.
The reticular formation is a network of neurons located in the brainstem that serves important functions. It extends from the spinal cord up through the midbrain. The reticular formation receives input from various areas of the brain and spinal cord and sends output to many regions including the thalamus and cerebral cortex. It is involved in arousal, motor control, sensory processing, sleep-wake cycles and other vital functions through the ascending and descending reticular activating systems. Damage to or disruption of the reticular formation can impact consciousness, muscle tone, learning, and circadian rhythms.
The document discusses the thalamus and its functions. It begins with objectives and physiological anatomy of the thalamus. It then discusses the internal structure of the thalamus including its white and grey matter. Next, it covers the connections of the thalamus including its sensory, motor, visceral, and integrative nuclei. It lists the functions of the thalamus such as acting as a sensory relay center and in arousal, perception, emotions, and motor integration. Finally, it discusses some applied aspects including thalamic syndrome, Korsakoff's syndrome, and frontal lobotomy.
The thalamus is a paired, oval structure located in the diencephalon that serves as a relay center for sensory and motor signals to and from the cerebral cortex. It is divided into several nuclei that process different sensory modalities. The thalamus receives input from various areas and projects to specific regions of the cortex. Damage to certain thalamic nuclei can disrupt motor control, sensory processing, and cause syndromes like thalamic pain. Surgical procedures targeting thalamic nuclei have been used to treat chronic pain conditions.
The thalamus is a paired symmetrical structure located in the center of the brain that relays sensory and motor signals between the brainstem and cerebral cortex. It is divided into several nuclei that have distinct connections and functions. The document provides detailed information on the anatomy, physiology, functional organization and clinical syndromes associated with lesions of different thalamic nuclei. Key points include a description of the gross anatomy and location of the thalamus, its blood supply, the nuclei and their connections, and syndromes associated with infarcts in the posterolateral and medial thalamic territories.
Anatomy of thalamus,Nuclei of thalamus,functional classification of thalamic nuclei,afferent and efferent connections of thalamus,motor function of thalamus,alertness and arousal in thalamus,thalamus and emotional behavior,Thalamic syndrome,Korsakoff's Syndrome
The pons lies between the medulla oblongata and midbrain, connecting them. It contains motor and sensory nuclei for cranial nerves 5-8 and helps transmit signals between the cerebellum and cerebral cortex. The pons has anterior and posterior surfaces and contains fibers, nuclei, and tracts that process sensory information and coordinate motor functions. Damage to different areas can cause deficits like hemiplegia, hearing loss, or facial paralysis.
The limbic system is a set of brain structures located deep in the brain that are involved in emotion, behavior, motivation, long-term memory, and olfaction. It includes the hippocampus, amygdala, and surrounding cortical areas. The hippocampus plays a key role in memory formation and storage. The amygdala is involved in emotional responses and regulating autonomic functions. Damage to limbic structures like the hippocampus and amygdala can result in conditions like Kluver-Bucy syndrome, anxiety, schizophrenia, and memory disorders.
The reticular formation is a network of neurons located in the brainstem that serves important functions. It extends from the spinal cord up through the midbrain. The reticular formation receives input from various areas of the brain and spinal cord and sends output to many regions including the thalamus and cerebral cortex. It is involved in arousal, motor control, sensory processing, sleep-wake cycles and other vital functions through the ascending and descending reticular activating systems. Damage to or disruption of the reticular formation can impact consciousness, muscle tone, learning, and circadian rhythms.
The document discusses the thalamus and its functions. It begins with objectives and physiological anatomy of the thalamus. It then discusses the internal structure of the thalamus including its white and grey matter. Next, it covers the connections of the thalamus including its sensory, motor, visceral, and integrative nuclei. It lists the functions of the thalamus such as acting as a sensory relay center and in arousal, perception, emotions, and motor integration. Finally, it discusses some applied aspects including thalamic syndrome, Korsakoff's syndrome, and frontal lobotomy.
The thalamus is a paired, oval structure located in the diencephalon that serves as a relay center for sensory and motor signals to and from the cerebral cortex. It is divided into several nuclei that process different sensory modalities. The thalamus receives input from various areas and projects to specific regions of the cortex. Damage to certain thalamic nuclei can disrupt motor control, sensory processing, and cause syndromes like thalamic pain. Surgical procedures targeting thalamic nuclei have been used to treat chronic pain conditions.
The thalamus is a paired symmetrical structure located in the center of the brain that relays sensory and motor signals between the brainstem and cerebral cortex. It is divided into several nuclei that have distinct connections and functions. The document provides detailed information on the anatomy, physiology, functional organization and clinical syndromes associated with lesions of different thalamic nuclei. Key points include a description of the gross anatomy and location of the thalamus, its blood supply, the nuclei and their connections, and syndromes associated with infarcts in the posterolateral and medial thalamic territories.
Anatomy of thalamus,Nuclei of thalamus,functional classification of thalamic nuclei,afferent and efferent connections of thalamus,motor function of thalamus,alertness and arousal in thalamus,thalamus and emotional behavior,Thalamic syndrome,Korsakoff's Syndrome
The pons lies between the medulla oblongata and midbrain, connecting them. It contains motor and sensory nuclei for cranial nerves 5-8 and helps transmit signals between the cerebellum and cerebral cortex. The pons has anterior and posterior surfaces and contains fibers, nuclei, and tracts that process sensory information and coordinate motor functions. Damage to different areas can cause deficits like hemiplegia, hearing loss, or facial paralysis.
Pyramidal tract by Sunita.M.Tiwale,Prof. Dept of physiology,D.Y.Patil Medical...Physiology Dept
Specific Learning Objectives:
At the end of session the students should be able to :
Enumerate the descending tracts.
Describe the origin, course, termination, collaterals of Pyramidal tract.
Describe the functions of the pyramidal tract.
The limbic system is a set of brain structures located in the midbrain and temporal lobes that are involved in emotion, behavior, motivation, learning, and memory. It includes structures like the hypothalamus, hippocampus, amygdala, septum, and limbic cortex. These structures work together and interact with other parts of the brain to control functions like pleasure and punishment, emotional responses, learning and memory formation. The limbic system plays an important role in regulating behaviors, emotions, and the formation of memories.
The document provides an overview of the basal ganglia. It discusses the physiological anatomy and components of the basal ganglia, including the caudate nucleus, putamen, globus pallidus, substantia nigra, and subthalamic nucleus. It describes the connections and functional neuronal circuits of the basal ganglia. The functions of the basal ganglia in motor control and disorders such as Parkinson's disease, chorea, athetosis, and Huntington's disease are summarized.
The document discusses the basal ganglia, which are a group of subcortical gray matter structures in the cerebrum that include the corpus striatum, amygdala, and claustrum. It describes the main components and connections of the basal ganglia, including the striatum, globus pallidus, substantia nigra, and subthalamic nucleus. The basal ganglia are involved in coordinating movement through connections with the cerebral cortex, thalamus, and brainstem. Disorders like Parkinson's disease can result from basal ganglia dysfunction and cause issues like tremors, rigidity, and bradykinesia.
The cerebellum is located behind the brainstem and contains only 10% of the brain's volume. It receives input from muscles, joints, and the motor cortex, and provides corrective signals to the motor cortex to coordinate voluntary movement. The cerebellum evaluates and adjusts motor movements, integrating sensory information to ensure balance and motor learning. Damage to different parts of the cerebellum results in difficulties with coordination, posture, movement timing and sequencing.
The parts of the brain include the cerebrum, thalamus, internal capsule, basal nuclei, hypothalamus, midbrain, pons varolii, cerebellum, and medulla oblongata. The cerebrum has lobes including the frontal, parietal, temporal, and occipital lobes. The thalamus relays sensory information to the cerebral cortex. The basal ganglia influence voluntary movements and posture. The internal capsule contains projection fibers connecting the cerebral cortex to lower parts of the brain. The cerebellum coordinates movement and balance.
The document provides an overview of the cerebellum including its:
- Physiological anatomy, divisions, and histological structure
- Neural circuits and neuronal activity
- Connections with other parts of the brain and spinal cord
- Key functions in controlling posture, balance, muscle tone, and voluntary movement
- Effects of cerebellar lesions and clinical tests used to assess cerebellar dysfunction
The basal ganglia are a group of interconnected brain structures that include the caudate nucleus, putamen, globus pallidus, subthalamic nucleus, and substantia nigra. They are involved in regulating movement and certain movement disorders. The basal ganglia receive input from the cortex and thalamus and send output to the thalamus and brainstem areas. Dopamine from the substantia nigra helps modulate input and output signaling in the basal ganglia circuits. Disorders of these circuits can result in dyskinesias like tremors, chorea, athetosis, and ballismus or disturbances of muscle tone.
The basal ganglia are large masses of gray matter located in the cerebral hemispheres. They are comprised of the caudate nucleus, lentiform nucleus (putamen and globus pallidus), amygdaloid nuclear complex, and claustrum. The basal ganglia receive input from the cerebral cortex and thalamus and output mainly to the globus pallidus and substantia nigra. They are involved in motor control and planning through direct and indirect pathways that facilitate or inhibit motor activity. Disorders like Parkinson's and Huntington's result from disruptions to these circuits.
The thalamus is a structure located in the middle of the brain between the cerebral cortex and midbrain. It is the largest component of the diencephalon. The thalamus acts as a relay station for sensory information (except smell) sending signals to the appropriate areas of the cerebral cortex. It is divided into nuclei that each have distinct functions and connections related to motor control, sensory processing and integration, arousal, memory and cognition. Damage to different thalamic nuclei can disrupt various functions and result in sensory deficits, movement problems or changes to consciousness.
The document discusses brain anatomy, specifically focusing on sulci and gyri. It provides definitions for sulci as depressions in the brain surface and gyri as ridges surrounded by sulci. Several major sulci are named, including the interhemispheric fissure, sylvian fissure, parieto-occipital fissure, and central sulcus. The four main lobes of the brain - frontal, parietal, temporal, and occipital - are also described based on their positioning relative to sulci. Each lobe contains gyri and sulci, and key structures like the precentral and postcentral gyri are identified.
The white matter of the cerebrum contains three main types of nerve fibers: commissural fibers, association fibers, and projection fibers. Commissural fibers such as the corpus callosum connect the two cerebral hemispheres. Association fibers like the superior longitudinal bundle connect different regions within the same hemisphere. Projection fibers including those in the internal capsule connect the cerebral cortex to lower brain centers. The internal capsule specifically contains fibers that project to and from the cortex and plays an important role in motor function. Damage to the internal capsule can thus cause contralateral hemiplegia.
1). The reticular formation is an ill-defined region in the brainstem comprising neurons and fibers that extends from the spinal cord to the thalamus. It is involved in arousal, attention, sleep-wake cycles, and autonomic functions.
2). The ascending reticular activating system projects from the brainstem reticular formation to the thalamus and cortex, promoting wakefulness. The descending pathway projects to the spinal cord and is involved in motor function.
3). The reticular formation receives inputs from sensory systems and projects to the thalamus, hypothalamus, and spinal cord. It regulates functions like muscle tone, respiration, cardiovascular control, and endocrine secretion.
The hypothalamus controls many essential functions through its connections with the pituitary gland and autonomic nervous system. It regulates homeostasis, hormone production and secretion, circadian rhythms, temperature, hunger and thirst, sleep cycles, emotions, and reproductive functions. The hypothalamus is located below the thalamus and forms part of the walls and floor of the third ventricle. It is divided into four levels - preoptic, supraoptic, tuberal, and mammillary - which contain nuclei that integrate homeostatic processes and regulate the endocrine and autonomic nervous systems.
The reticular formation is a network of neurons located in the brainstem that performs several important functions. It receives sensory information from the spinal cord and senses arousal levels. The reticular formation contains nuclei that are involved in motor control, sleep-wake cycles, autonomic functions, and modulating pain. It has ascending and descending pathways that connect to the thalamus and cerebral cortex and help regulate states of consciousness like sleep and wakefulness.
The limbic system is a ring of structures located deep within the brain that are involved in emotion, motivation, learning, and memory. It includes structures like the hippocampus, amygdala, hypothalamus, and cingulate gyrus. The limbic system regulates emotional responses, controls certain autonomic functions like breathing and heart rate, influences reward and punishment behaviors, and plays a role in forming memories and social cognition. Dysfunctions of the limbic system are implicated in various neurological and psychiatric conditions like epilepsy, dementia, anxiety disorders, and schizophrenia.
The brain stem is located between the cerebrum and spinal cord, and consists of the midbrain, pons, and medulla oblongata. The midbrain connects the forebrain to the pons and cerebellum. It contains important centers for visual and auditory reflexes, and gives rise to the trochlear nerve. Key structures in the midbrain include the superior and inferior colliculi, oculomotor nucleus, red nucleus, and substantia nigra. The midbrain serves to relay motor and sensory signals between the spinal cord and forebrain.
The pons is located in the brainstem, between the midbrain and medulla oblongata. It contains fibers that connect the cerebellum and cerebrum, and nuclei for several cranial nerves including the trigeminal, facial, and abducent nerves. The pons receives its blood supply primarily from the basilar artery and its branches, as well as the anterior inferior cerebellar and superior cerebellar arteries. It plays an important role in motor functions and sensory processes.
The document discusses the limbic system, which is a set of brain structures involved in emotion, learning, and memory. It includes the hippocampus, amygdala, hypothalamus, and connections between cortical and subcortical regions. The limbic system regulates many functions including emotion, learning, memory formation, and autonomic nervous system activity. Key structures like the hippocampus and amygdala each have distinct roles - the hippocampus is important for memory formation while the amygdala processes emotions. Lesions in different limbic system areas can impact neurophysiological functions and lead to effects on behaviors regulated by that region.
Reticular formation in control of motor functionsTural Abdullayev
The reticular formation is located in the central core of the brainstem and controls motor functions through direct and indirect projections. It contains two reticulospinal tracts - the medial and lateral tracts - that project to different regions of the spinal cord and modulate muscle tone, reflexes, posture, and movement. The reticular formation also projects to motor control centers in the brainstem, cerebellum, basal ganglia, and cortex to regulate skeletal muscle activity during facial expressions, voluntary movement, respiration, and maintaining balance and posture.
The document discusses the reticular activating system and its role in consciousness and sleep. It notes that the reticular activating system is a collection of neurons in the brain stem that secretes different transmitters and connects specific portions of the thalamus to areas of the cerebral cortex. This system plays an important role in regulating states of consciousness and sleep through synchronization and desynchronization of brain waves.
Pyramidal tract by Sunita.M.Tiwale,Prof. Dept of physiology,D.Y.Patil Medical...Physiology Dept
Specific Learning Objectives:
At the end of session the students should be able to :
Enumerate the descending tracts.
Describe the origin, course, termination, collaterals of Pyramidal tract.
Describe the functions of the pyramidal tract.
The limbic system is a set of brain structures located in the midbrain and temporal lobes that are involved in emotion, behavior, motivation, learning, and memory. It includes structures like the hypothalamus, hippocampus, amygdala, septum, and limbic cortex. These structures work together and interact with other parts of the brain to control functions like pleasure and punishment, emotional responses, learning and memory formation. The limbic system plays an important role in regulating behaviors, emotions, and the formation of memories.
The document provides an overview of the basal ganglia. It discusses the physiological anatomy and components of the basal ganglia, including the caudate nucleus, putamen, globus pallidus, substantia nigra, and subthalamic nucleus. It describes the connections and functional neuronal circuits of the basal ganglia. The functions of the basal ganglia in motor control and disorders such as Parkinson's disease, chorea, athetosis, and Huntington's disease are summarized.
The document discusses the basal ganglia, which are a group of subcortical gray matter structures in the cerebrum that include the corpus striatum, amygdala, and claustrum. It describes the main components and connections of the basal ganglia, including the striatum, globus pallidus, substantia nigra, and subthalamic nucleus. The basal ganglia are involved in coordinating movement through connections with the cerebral cortex, thalamus, and brainstem. Disorders like Parkinson's disease can result from basal ganglia dysfunction and cause issues like tremors, rigidity, and bradykinesia.
The cerebellum is located behind the brainstem and contains only 10% of the brain's volume. It receives input from muscles, joints, and the motor cortex, and provides corrective signals to the motor cortex to coordinate voluntary movement. The cerebellum evaluates and adjusts motor movements, integrating sensory information to ensure balance and motor learning. Damage to different parts of the cerebellum results in difficulties with coordination, posture, movement timing and sequencing.
The parts of the brain include the cerebrum, thalamus, internal capsule, basal nuclei, hypothalamus, midbrain, pons varolii, cerebellum, and medulla oblongata. The cerebrum has lobes including the frontal, parietal, temporal, and occipital lobes. The thalamus relays sensory information to the cerebral cortex. The basal ganglia influence voluntary movements and posture. The internal capsule contains projection fibers connecting the cerebral cortex to lower parts of the brain. The cerebellum coordinates movement and balance.
The document provides an overview of the cerebellum including its:
- Physiological anatomy, divisions, and histological structure
- Neural circuits and neuronal activity
- Connections with other parts of the brain and spinal cord
- Key functions in controlling posture, balance, muscle tone, and voluntary movement
- Effects of cerebellar lesions and clinical tests used to assess cerebellar dysfunction
The basal ganglia are a group of interconnected brain structures that include the caudate nucleus, putamen, globus pallidus, subthalamic nucleus, and substantia nigra. They are involved in regulating movement and certain movement disorders. The basal ganglia receive input from the cortex and thalamus and send output to the thalamus and brainstem areas. Dopamine from the substantia nigra helps modulate input and output signaling in the basal ganglia circuits. Disorders of these circuits can result in dyskinesias like tremors, chorea, athetosis, and ballismus or disturbances of muscle tone.
The basal ganglia are large masses of gray matter located in the cerebral hemispheres. They are comprised of the caudate nucleus, lentiform nucleus (putamen and globus pallidus), amygdaloid nuclear complex, and claustrum. The basal ganglia receive input from the cerebral cortex and thalamus and output mainly to the globus pallidus and substantia nigra. They are involved in motor control and planning through direct and indirect pathways that facilitate or inhibit motor activity. Disorders like Parkinson's and Huntington's result from disruptions to these circuits.
The thalamus is a structure located in the middle of the brain between the cerebral cortex and midbrain. It is the largest component of the diencephalon. The thalamus acts as a relay station for sensory information (except smell) sending signals to the appropriate areas of the cerebral cortex. It is divided into nuclei that each have distinct functions and connections related to motor control, sensory processing and integration, arousal, memory and cognition. Damage to different thalamic nuclei can disrupt various functions and result in sensory deficits, movement problems or changes to consciousness.
The document discusses brain anatomy, specifically focusing on sulci and gyri. It provides definitions for sulci as depressions in the brain surface and gyri as ridges surrounded by sulci. Several major sulci are named, including the interhemispheric fissure, sylvian fissure, parieto-occipital fissure, and central sulcus. The four main lobes of the brain - frontal, parietal, temporal, and occipital - are also described based on their positioning relative to sulci. Each lobe contains gyri and sulci, and key structures like the precentral and postcentral gyri are identified.
The white matter of the cerebrum contains three main types of nerve fibers: commissural fibers, association fibers, and projection fibers. Commissural fibers such as the corpus callosum connect the two cerebral hemispheres. Association fibers like the superior longitudinal bundle connect different regions within the same hemisphere. Projection fibers including those in the internal capsule connect the cerebral cortex to lower brain centers. The internal capsule specifically contains fibers that project to and from the cortex and plays an important role in motor function. Damage to the internal capsule can thus cause contralateral hemiplegia.
1). The reticular formation is an ill-defined region in the brainstem comprising neurons and fibers that extends from the spinal cord to the thalamus. It is involved in arousal, attention, sleep-wake cycles, and autonomic functions.
2). The ascending reticular activating system projects from the brainstem reticular formation to the thalamus and cortex, promoting wakefulness. The descending pathway projects to the spinal cord and is involved in motor function.
3). The reticular formation receives inputs from sensory systems and projects to the thalamus, hypothalamus, and spinal cord. It regulates functions like muscle tone, respiration, cardiovascular control, and endocrine secretion.
The hypothalamus controls many essential functions through its connections with the pituitary gland and autonomic nervous system. It regulates homeostasis, hormone production and secretion, circadian rhythms, temperature, hunger and thirst, sleep cycles, emotions, and reproductive functions. The hypothalamus is located below the thalamus and forms part of the walls and floor of the third ventricle. It is divided into four levels - preoptic, supraoptic, tuberal, and mammillary - which contain nuclei that integrate homeostatic processes and regulate the endocrine and autonomic nervous systems.
The reticular formation is a network of neurons located in the brainstem that performs several important functions. It receives sensory information from the spinal cord and senses arousal levels. The reticular formation contains nuclei that are involved in motor control, sleep-wake cycles, autonomic functions, and modulating pain. It has ascending and descending pathways that connect to the thalamus and cerebral cortex and help regulate states of consciousness like sleep and wakefulness.
The limbic system is a ring of structures located deep within the brain that are involved in emotion, motivation, learning, and memory. It includes structures like the hippocampus, amygdala, hypothalamus, and cingulate gyrus. The limbic system regulates emotional responses, controls certain autonomic functions like breathing and heart rate, influences reward and punishment behaviors, and plays a role in forming memories and social cognition. Dysfunctions of the limbic system are implicated in various neurological and psychiatric conditions like epilepsy, dementia, anxiety disorders, and schizophrenia.
The brain stem is located between the cerebrum and spinal cord, and consists of the midbrain, pons, and medulla oblongata. The midbrain connects the forebrain to the pons and cerebellum. It contains important centers for visual and auditory reflexes, and gives rise to the trochlear nerve. Key structures in the midbrain include the superior and inferior colliculi, oculomotor nucleus, red nucleus, and substantia nigra. The midbrain serves to relay motor and sensory signals between the spinal cord and forebrain.
The pons is located in the brainstem, between the midbrain and medulla oblongata. It contains fibers that connect the cerebellum and cerebrum, and nuclei for several cranial nerves including the trigeminal, facial, and abducent nerves. The pons receives its blood supply primarily from the basilar artery and its branches, as well as the anterior inferior cerebellar and superior cerebellar arteries. It plays an important role in motor functions and sensory processes.
The document discusses the limbic system, which is a set of brain structures involved in emotion, learning, and memory. It includes the hippocampus, amygdala, hypothalamus, and connections between cortical and subcortical regions. The limbic system regulates many functions including emotion, learning, memory formation, and autonomic nervous system activity. Key structures like the hippocampus and amygdala each have distinct roles - the hippocampus is important for memory formation while the amygdala processes emotions. Lesions in different limbic system areas can impact neurophysiological functions and lead to effects on behaviors regulated by that region.
Reticular formation in control of motor functionsTural Abdullayev
The reticular formation is located in the central core of the brainstem and controls motor functions through direct and indirect projections. It contains two reticulospinal tracts - the medial and lateral tracts - that project to different regions of the spinal cord and modulate muscle tone, reflexes, posture, and movement. The reticular formation also projects to motor control centers in the brainstem, cerebellum, basal ganglia, and cortex to regulate skeletal muscle activity during facial expressions, voluntary movement, respiration, and maintaining balance and posture.
The document discusses the reticular activating system and its role in consciousness and sleep. It notes that the reticular activating system is a collection of neurons in the brain stem that secretes different transmitters and connects specific portions of the thalamus to areas of the cerebral cortex. This system plays an important role in regulating states of consciousness and sleep through synchronization and desynchronization of brain waves.
The reticular activating system (RAS) is a complex network of neurons located in the brainstem that regulates states of consciousness such as sleep and wakefulness. It is composed of neurotransmitter systems including cholinergic, adrenergic, serotonergic, and histaminergic neurons. The RAS maintains arousal and attention by transmitting signals from the brainstem to the thalamus and cortex. Disruptions in the RAS can result in disturbances of consciousness and sleep-wake cycles, and have been implicated in disorders such as schizophrenia, PTSD, Parkinson's disease, and Alzheimer's disease.
The reticular formation is a network of neurons located in the brainstem that serves several important functions:
1. It helps regulate arousal and consciousness through the reticular activating system. This system projects to the thalamus and maintains an alert cerebral cortex. Damage can result in coma.
2. It modulates muscle tone through facilitatory and inhibitory projections to the spinal cord. The pontine reticular formation facilitates antigravity muscles while the medullary region inhibits them.
3. In addition to arousal and motor control, the reticular formation is involved in other autonomic functions like respiration, cardiovascular regulation, vomiting, coughing, and processing pain signals.
This document discusses cholinergic and noradrenergic neurons. Cholinergic neurons are excitatory or inhibitory and include motor neurons, all autonomic preganglionic neurons, and postganglionic parasympathetic neurons. The basal forebrain complex provides cholinergic innervation to the hippocampus and neocortex and is involved in regulating arousal, sleep-wake cycles, and learning and memory. The pontomesencephalotegmental complex projects to the thalamus and regulates sensory relay nuclei. Noradrenergic neurons are located in the locus coeruleus and project widely throughout the central nervous system, regulating attention, arousal, sleep-wake cycles, learning, mood, and brain metabolism
The document discusses the reticular activating system (RAS), which is a network of neurons in the brainstem that regulates states of consciousness and sleep-wake cycles. Stimulation of different areas of the reticular formation can increase or decrease spinal reflexes. The RAS includes noradrenergic, dopaminergic, serotonergic, and cholinergic neurons that project ascending signals to the thalamus and cortex. Damage to parts of the RAS can impair consciousness. Sleep involves circadian rhythms and cycles through non-REM and REM sleep stages, each with different patterns of neuronal activity and physiological changes.
The reticular formation is a region in the brainstem that regulates consciousness and brain activity. It consists of three columns of nuclei extending from the spinal cord to the thalamus. The reticular formation receives all peripheral sensory information and is capable of activating large areas of the thalamus and cortex. It regulates levels of alertness and consciousness based on sensory information received, elevating brain activity during wakefulness and allowing sleep when input is diminished.
1) Muscle tone is a state of partial contraction of resting muscle that maintains body posture through continuous motor impulses from reflexes.
2) Muscle spindles are stretch receptors that provide sensory feedback on muscle length and rate of stretch. Their afferents signal to the CNS and regulate motor neuron activity.
3) Spasticity results from loss of supraspinal control over reflexes after upper motor neuron injury, causing velocity-dependent increases in tonic stretch reflexes and impaired voluntary movement.
Medulla, Reticular Formation, Thalamus, and HippocampusCArndt13
The medulla regulates vital involuntary functions like breathing and heart rate. Damage to the medulla is often fatal or causes vegetative states, as it controls crucial tasks necessary for life. The reticular formation in the medulla regulates arousal, attention, sleep, and awareness. Damage can cause fatigue, sexual dysfunction, or coma. The thalamus relays sensory information to processing areas. Damage results in sensory confusion as information is wrongly directed. The hippocampus processes long-term memory and emotions. Alzheimer's or damage impairs memory formation and recall of object and event locations.
The reticular formation is a region in the brainstem that contains a network of neurons and fibers. It receives sensory information from ascending and descending tracts and has connections with other brain regions. It contains four important neuronal systems - the gigantocellular nuclei, substantia nigra, locus ceruleus, and raphe nuclei. The reticular formation plays roles in consciousness, sleep, sensory regulation, motor control, and autonomic functions through these neuronal systems.
The Reticular Activating System (RAS) is a network of neurons that extends from the brainstem to different parts of the brain and spinal cord. It functions to regulate arousal, alertness, and selective attention by increasing or decreasing activity and directing cortical areas to focus on relevant information. Destroying the RAS causes a coma similar to sleep, while stimulating it instantly awakens sleeping animals. The Thalamus filters and relays incoming sensory information, with the exception of smell, to cortical areas. It plays a role in attention by emphasizing certain information and regulates arousal through its connection to the RAS.
1) Muscle tone is maintained by low-level muscle contractions regulated by the brain and spinal cord. Muscle spindles within muscles provide feedback on tone levels.
2) When a muscle is stretched, muscle spindles activate the stretch reflex, causing the muscle to contract and counteract the stretch. This maintains constant tone.
3) Gamma motor neurons contract intrafusal muscle fibers within spindles to keep spindles "in tune" as muscle tone levels change, allowing precise tone regulation. Spindle feedback continually informs the brain, especially the cerebellum, of tone levels.
This document describes various approaches to the petrous apex, including the middle cranial fossa transpetrous approach. It discusses the landmarks and surgical anatomy relevant to this approach, including exposing the internal auditory canal and petrous apex by drilling bone. It also mentions combining the frontotemporal orbitozygomatic approach with the Kawase approach to access the middle and posterior cranial fossae. Several references are provided with links to videos and papers on these techniques.
The kidneys regulate plasma and interstitial fluid by forming urine. This regulates blood volume, waste products, electrolyte concentrations, and pH. There are cortical and juxtamedullary nephrons. Glomerular filtration, tubular reabsorption, and secretion work together to regulate urine formation and blood composition. Filtration occurs as fluid passes through the glomerular capillaries, and the resulting filtrate enters the nephron tubules. Most of the filtrate is reabsorbed back into circulation as it passes through the tubules, resulting in concentrated urine.
The vestibular system detects head motion and orientation using receptors in the inner ear. It has three main functions: coordinating eye and head movements, maintaining balance and posture, and perceiving spatial orientation. The vestibular system interacts with the brainstem, cerebellum, eyes, spinal cord and muscles. Sensory information travels to the brainstem via the vestibular nerve and projects to areas controlling eye movements, posture and spatial awareness. Damage can cause issues with balance, coordination and perception.
This document discusses the anatomy and development of the brain stem. It begins with an overview of the three main regions of the brain stem - the medulla, pons, and midbrain. It then examines the development of the brain stem and cranial nerves in the early stages of gestation. The majority of the document focuses on detailed images and descriptions of the gross and microscopic anatomy of structures within the brain stem, including nuclei, tracts, and cranial nerve pathways.
Physiology of posture movementand equilibriumwebzforu
This document discusses the physiology of posture, movement, and equilibrium. It covers 3 main points:
1. The neural control of posture and movement involves pathways from the cortex, brainstem, and cerebellum that converge on spinal motor neurons. The pyramidal system controls voluntary movement while the extrapyramidal system adjusts posture.
2. Lesions to different parts of the motor control pathways produce distinct deficits, such as loss of fine motor skills from damage to the lateral corticospinal tract. Transections of the spinal cord and brainstem in animals produce characteristic reflexes and rigidity.
3. The brainstem, cerebellum, and vestibular systems work together to maintain equilibrium and
1. The document discusses various postural reflexes that help maintain upright posture and balance. It describes segmental, tonic, and righting reflexes in detail.
2. Segmental reflexes like the stretch reflex and crossed extensor reflex act at the spinal cord level. Tonic reflexes like the tonic neck reflex integrate signals at the medulla. Righting reflexes like the labyrinthine righting reflex restore posture at the midbrain level.
3. Experimental preparations are used to study the postural reflexes at different levels, including spinal, decerebrate, midbrain, thalamic, and decorticate preparations. Decerebrate animals exhibit decerebrate
The document discusses the vestibular system, which detects angular and linear acceleration of the head. It has two main parts: the semicircular canals and otolith organs. The semicircular canals contain hair cells that detect rotational movement and signal the brain. The otolith organs contain hair cells and calcium crystals that detect gravity and linear acceleration. The vestibular system provides input to areas of the brainstem, cerebellum and cortex that are important for balance, posture, eye movements and awareness of head position. It discusses the anatomy and function of the vestibular system and several reflexes it controls like the vestibulo-ocular reflex.
Review Of Anatomy And Physiology Of The Nervousmycomic
The document reviews the anatomy and physiology of the nervous system. It describes the central nervous system (brain and spinal cord) and peripheral nervous system. It discusses the structure and function of neurons, classification of neurons, and the components and roles of the nervous system including the brain, spinal cord, cranial nerves and vascular supply. It provides an overview of the organization, tissues and pathways involved in the nervous system.
The reticular formation is a diffuse mass of neurons and fibers in the brainstem that regulates vital functions like consciousness, respiration, blood pressure, and muscle tone. It receives inputs from sensory systems and connects to all levels of the central nervous system. The reticular formation contains nuclei that can be divided into median, medial, and lateral columns based on neuron size. These nuclei have ascending and descending connections and are involved in arousal, sensory modulation, and motor control. The reticular formation plays an important role in regulating consciousness, autonomic functions, and motor activity through its widespread connections throughout the brain and spinal cord.
This document provides an overview of neurophysiology and various parts of the central nervous system. It discusses the brain stem and its three parts - medulla oblongata, pons, and midbrain. It then explains the reticular formation and its role in regulating states of consciousness. The document also reviews the cerebellum's anatomical structures and functions in motor control. The basal nuclei and limbic system are listed but not described. Overall, the document summarizes key areas and functions of the brain stem, reticular formation, and cerebellum.
The cerebellum plays an important role in motor control and coordination. It receives input from various sources, including the spinal cord, brainstem, and cerebral cortex. This input is processed within the cerebellar cortex and nuclei. The cerebellum then sends output to motor areas of the brainstem and cerebral cortex to coordinate movement, balance, and posture. It acts as a comparator, receiving feedback on actual movements and comparing them to intended movements, in order to calibrate motor output and prevent overshooting during voluntary motor acts such as walking and running. Damage to the cerebellum can cause ataxia or lack of coordination.
The anatomy and physiology of nervous with quick overview
OBJECTIVES
1. I can describe the functions of the nervous system
2. I can describe the parts of a neuron cell and identify how they transmit electrochemical impulses.
3. I can compare and contrast the central and peripheral nervous systems
4. I can identify and explain different areas of the brain and their functions.
5. I can explain how the nervous system passes information between the external environment and the many parts of the body.
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authentic medical material
The document provides an overview of the central nervous system. It discusses the main components and functions of the CNS, including the brain stem, cerebellum, basal ganglia, thalamus, hypothalamus, hippocampus, and amygdala. It also covers topics like neuron types, neuroglia, CSF circulation, spinal cord levels, lower and higher brain functions, speech pathways, and neurodegenerative diseases. The central topics covered are the structure and functions of the key parts of the CNS and their roles in motor control, sensory processing, memory, emotion and other higher cognitive functions.
The document discusses various extrapyramidal tracts in the brain and spinal cord that help control motor function. It describes the rubrospinal, reticulospinal, olivospinal, tectospinal, and vestibulospinal tracts, including their origins, pathways, and functions. Common extrapyramidal disorders like Parkinson's disease, chorea, hemiballism, athetosis, dystonia, and tardive dyskinesia are also briefly outlined.
CENTRAL NERVOUS SYSTEM PHARMACOLOGY PPT KIU.pptxYIKIISAAC
This document provides an overview of the central nervous system (CNS) and its organization. It discusses the major divisions and regions of the brain including the cerebral cortex, limbic system, diencephalon, midbrain, brainstem, cerebellum, and spinal cord. It describes the cellular organization and microanatomy of the brain, focusing on neurons, synapses, and neurotransmission. The document also provides a course synopsis on topics in CNS pharmacology.
The document provides information about the cerebellum including its anatomical subdivisions, development, functional organization, and connections. It discusses the phylogenetic organization of the spinocerebellum, pontocerebellum, and vestibulocerebellum. It also summarizes the functions of the archicerebellum, paleocerebellum, and neocerebellum as well as cerebellar abnormalities caused by lesions in different areas.
The document discusses the structure and function of the human neural and sensory systems. It describes the central nervous system including the brain, spinal cord, and peripheral nervous system. It explains the divisions of the brain including the forebrain, midbrain, and hindbrain. It also discusses the autonomic nervous system and its sympathetic and parasympathetic divisions. Additionally, it summarizes the structure and function of the eye and ear as sensory organs.
The midbrain connects the brainstem to the forebrain and cerebellum. It consists of the tectum and cerebral peduncles. The tectum contains the superior and inferior colliculi, which are involved in visual and auditory reflexes. The cerebral peduncles contain the substantia nigra and red nucleus. The red nucleus receives input from the motor cortex and dentate nucleus, and sends outputs to control muscle tone, complex movements, righting reflexes, and eye movements.
The document summarizes key aspects of the brainstem. It discusses the brainstem's functions including serving as a conduit for ascending and descending tracts between the spinal cord and thalamus/cerebellum. It describes the internal structure and locations of tracts through the medulla, pons, and midbrain. The cranial nerve nuclei are located throughout the brainstem, organized into somatic and visceral sensory/motor columns. Major fiber decussations occur at the pyramidal decussation, medial lemniscus, and dentatothalamic tract.
A brief discussion on nervous system. central nervous system its part like a short note on brain according to b.pharma 2nd semester syllabus. short note on neurones, neurotransmitter,
The document provides information on the anatomy, physiology, and functions of the cerebellum. Some key points:
- The cerebellum is located in the posterior cranial fossa below the tentorium cerebelli. It has three lobes and consists of an outer cortex and inner white matter.
- It is involved in motor control and coordination, balance, posture, and motor learning. Recent evidence also suggests roles in cognitive functions and affect regulation.
- Cerebellar circuits involve mossy and climbing fibers connecting to Purkinje cells and deep cerebellar nuclei. Damage can cause ataxia, nystagmus, dysmetria and other motor signs, as well as cognitive and psychiatric
The diencephalon includes structures like the thalamus, hypothalamus, epithalamus, and subthalamus. The thalamus relays sensory and motor signals to the cerebral cortex. It contains nuclei that relay specific sensations like vision, hearing, and somatosensation. The hypothalamus controls autonomic functions and regulates behaviors related to hunger, thirst, temperature, sleep, and reproduction. It also controls the pituitary gland. The epithalamus includes the pineal gland and habenular nucleus. The subthalamus contains the subthalamic nucleus and is involved in motor control.
CEREBELLUM- with clinical and radiologylalit yadav
The cerebellum is located in the posterior cranial fossa. It plays an important role in motor control and coordination by modulating posture, balance, and motor skills. The cerebellum receives input from various sources including the spinal cord, brainstem, and cerebral cortex. It has three lobes and contains densely packed neurons in the cerebellar cortex that communicate with deep cerebellar nuclei. Damage to different parts of the cerebellum can cause ataxia, impaired gait, or difficulties with coordinated voluntary movement.
The central nervous system consists of the brain and spinal cord. The brain is divided into the forebrain, midbrain, and hindbrain. The forebrain contains structures like the cerebral cortex that control functions like thinking and producing language. The midbrain regulates sensory processes and body movement. The hindbrain includes the cerebellum, pons, and medulla, which are involved in motor control, balance, and vital functions. The spinal cord connects the brain to the rest of the body and transmits motor and sensory signals.
- Video recording of this lecture in English language: https://youtu.be/Pt1nA32sdHQ
- Video recording of this lecture in Arabic language: https://youtu.be/uFdc9F0rlP0
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STUDIES IN SUPPORT OF SPECIAL POPULATIONS: GERIATRICS E7shruti jagirdar
Unit 4: MRA 103T Regulatory affairs
This guideline is directed principally toward new Molecular Entities that are
likely to have significant use in the elderly, either because the disease intended
to be treated is characteristically a disease of aging ( e.g., Alzheimer's disease) or
because the population to be treated is known to include substantial numbers of
geriatric patients (e.g., hypertension).
Debunking Nutrition Myths: Separating Fact from Fiction"AlexandraDiaz101
In a world overflowing with diet trends and conflicting nutrition advice, it’s easy to get lost in misinformation. This article cuts through the noise to debunk common nutrition myths that may be sabotaging your health goals. From the truth about carbohydrates and fats to the real effects of sugar and artificial sweeteners, we break down what science actually says. Equip yourself with knowledge to make informed decisions about your diet, and learn how to navigate the complexities of modern nutrition with confidence. Say goodbye to food confusion and hello to a healthier you!
Nutritional deficiency Disorder are problems in india.
It is very important to learn about Indian child's nutritional parameters as well the Disease related to alteration in their Nutrition.
Breast cancer: Post menopausal endocrine therapyDr. Sumit KUMAR
Breast cancer in postmenopausal women with hormone receptor-positive (HR+) status is a common and complex condition that necessitates a multifaceted approach to management. HR+ breast cancer means that the cancer cells grow in response to hormones such as estrogen and progesterone. This subtype is prevalent among postmenopausal women and typically exhibits a more indolent course compared to other forms of breast cancer, which allows for a variety of treatment options.
Diagnosis and Staging
The diagnosis of HR+ breast cancer begins with clinical evaluation, imaging, and biopsy. Imaging modalities such as mammography, ultrasound, and MRI help in assessing the extent of the disease. Histopathological examination and immunohistochemical staining of the biopsy sample confirm the diagnosis and hormone receptor status by identifying the presence of estrogen receptors (ER) and progesterone receptors (PR) on the tumor cells.
Staging involves determining the size of the tumor (T), the involvement of regional lymph nodes (N), and the presence of distant metastasis (M). The American Joint Committee on Cancer (AJCC) staging system is commonly used. Accurate staging is critical as it guides treatment decisions.
Treatment Options
Endocrine Therapy
Endocrine therapy is the cornerstone of treatment for HR+ breast cancer in postmenopausal women. The primary goal is to reduce the levels of estrogen or block its effects on cancer cells. Commonly used agents include:
Selective Estrogen Receptor Modulators (SERMs): Tamoxifen is a SERM that binds to estrogen receptors, blocking estrogen from stimulating breast cancer cells. It is effective but may have side effects such as increased risk of endometrial cancer and thromboembolic events.
Aromatase Inhibitors (AIs): These drugs, including anastrozole, letrozole, and exemestane, lower estrogen levels by inhibiting the aromatase enzyme, which converts androgens to estrogen in peripheral tissues. AIs are generally preferred in postmenopausal women due to their efficacy and safety profile compared to tamoxifen.
Selective Estrogen Receptor Downregulators (SERDs): Fulvestrant is a SERD that degrades estrogen receptors and is used in cases where resistance to other endocrine therapies develops.
Combination Therapies
Combining endocrine therapy with other treatments enhances efficacy. Examples include:
Endocrine Therapy with CDK4/6 Inhibitors: Palbociclib, ribociclib, and abemaciclib are CDK4/6 inhibitors that, when combined with endocrine therapy, significantly improve progression-free survival in advanced HR+ breast cancer.
Endocrine Therapy with mTOR Inhibitors: Everolimus, an mTOR inhibitor, can be added to endocrine therapy for patients who have developed resistance to aromatase inhibitors.
Chemotherapy
Chemotherapy is generally reserved for patients with high-risk features, such as large tumor size, high-grade histology, or extensive lymph node involvement. Regimens often include anthracyclines and taxanes.
Giloy in Ayurveda - Classical Categorization and SynonymsPlanet Ayurveda
Giloy, also known as Guduchi or Amrita in classical Ayurvedic texts, is a revered herb renowned for its myriad health benefits. It is categorized as a Rasayana, meaning it has rejuvenating properties that enhance vitality and longevity. Giloy is celebrated for its ability to boost the immune system, detoxify the body, and promote overall wellness. Its anti-inflammatory, antipyretic, and antioxidant properties make it a staple in managing conditions like fever, diabetes, and stress. The versatility and efficacy of Giloy in supporting health naturally highlight its importance in Ayurveda. At Planet Ayurveda, we provide a comprehensive range of health services and 100% herbal supplements that harness the power of natural ingredients like Giloy. Our products are globally available and affordable, ensuring that everyone can benefit from the ancient wisdom of Ayurveda. If you or your loved ones are dealing with health issues, contact Planet Ayurveda at 01725214040 to book an online video consultation with our professional doctors. Let us help you achieve optimal health and wellness naturally.
Are you looking for a long-lasting solution to your missing tooth?
Dental implants are the most common type of method for replacing the missing tooth. Unlike dentures or bridges, implants are surgically placed in the jawbone. In layman’s terms, a dental implant is similar to the natural root of the tooth. It offers a stable foundation for the artificial tooth giving it the look, feel, and function similar to the natural tooth.
5-hydroxytryptamine or 5-HT or Serotonin is a neurotransmitter that serves a range of roles in the human body. It is sometimes referred to as the happy chemical since it promotes overall well-being and happiness.
It is mostly found in the brain, intestines, and blood platelets.
5-HT is utilised to transport messages between nerve cells, is known to be involved in smooth muscle contraction, and adds to overall well-being and pleasure, among other benefits. 5-HT regulates the body's sleep-wake cycles and internal clock by acting as a precursor to melatonin.
It is hypothesised to regulate hunger, emotions, motor, cognitive, and autonomic processes.
The Children are very vulnerable to get affected with respiratory disease.
In our country, the respiratory Disease conditions are consider as major cause for mortality and Morbidity in Child.
2. n
OBJECTIVE
INTRODUCTION
LOCATION OF RETICULAR FORMATION
NUCLEI OF RETICULAR FORMATION(NEUROAL AGGREGATES )
AFFERENTS AND EFFERENT OF RETICULAR FORMATION
FUNCTIONS OF RETICULAR FORMATION
ASCENDING RETICULAR ACTIVATING SYSTEM
DESCENDING RETICULAR ACTIVATING SYSTEM
ROLE IN SLEEP AND WAKE FULLNES
APPLIED PHYSIOLOGY
3. The brainstem contains extensive fields of intermingled
neuronal cell bodies and nerve fibres, which are collectively
termed the reticular formation. The reticular regions are often
regarded as phylogenetically ancient, representing a primitive
nerve network on which more anatomically organized,
functionally selective connections have developed during
evolution
4.
5.
6. Reticular regions tend to be ill-defined collections of neurones with
diffuse connections. Their conduction paths are difficult to define,
often complex and polysynaptic, and they have ascending and
descending components that are crossed, uncrossed and
sometimes bilateral. Their components subserve somatic and
visceral functions.
7.
8.
9. They also include some distinct and important
cell groups, which are distinguished on the
basis of their conections and neurotransmitter
substances. These
Include:
dopaminergic and noradrenergic
neurones (group A)
serotoninergic (group B)
adrenergic (group C)
cholinergic (group Ch)
10.
11. . Some regions contain only small to
intermediate multipolar cells (‘parvocellular’
regions). However, there are a few areas where
these mingle with large multipolar neurones in
‘gigantocellular’ or ‘magnocellular’ nuclei.
12.
13. In general terms, the reticular formation is a continuous core that
traverses the whole brainstem, and is continuous below with the
reticular intermediate spinal grey. It is divisible, on the basis of
cytoarchitectonic, chemoarchitectonic and functional criteria, into
three bilateral longitudinal columns:
median; medial, containing mostly large reticular neurones; and
lateral, containing mostly small to intermediate neurones
14.
15.
16. MEDIAN COLUMNNUCLEI
midlineand occupyinthe median column of reticular nuclei extends
throughout the medulla, pons and midbrain and contains neurones that
are largely aggregated in bilateral, vertical sheets, located immediately
adjacent to the g the paramedian zones. collectively they are called the
nuclei of the raphe, or raphe nuclei. many neurones in raphe nuclei are
serotoninergic and are grouped into nine clusters, b1–9
17.
18. The raphe pallidus nucleus (B1) and associated raphe obscurus nucleus (B2) lie in the upper
two-thirds of the medulla and cross the pontomedullary junction. The raphe magnus nucleus,
corresponding to many B3 neurones, minimally overlaps with B1 and B2, and ascends into
the caudal pons. Above it is the pontine raphe nucleus, which is formed by cell group B5. Also
located in the pons is the central superior raphe nucleus, which contains parts of cell groups
B6 and B8. The dorsal (rostral) raphe nucleus, approximating to cell group B7, extends
through much of the midbrain.
19.
20. 1. Raphe nuclei of medulla:-
• Nucleus raphe obscures
• Nucleus raphe magnus
• Nucleus pallidus.
2. Raphe nuclei of the pontine reticular formation
• Pontine raphe nucleus
• Inferior central nucleus
3. Raphe nuclei of the Midbrain reticular
formation
• Superior central nucleus
• Dorsal Raphe nucleus
21.
22. all raphe nuclei provide descending serotoninergic projecti ons,which
terminate in the brainstem and spinal cord. Brainstem connections are
multiple and complex. For example, the dorsal raphe nucleus, in addition
to sending a large number of fibres to the locus coeruleus, projects to
the dorsal tegmental nucleus and most of the rhombencephalic reticular
formation, together with the central superior, pontine raphe and raphe
magnus nuclei.
23.
24.
25.
26. Raphe-spinal serotoninergic axons originate mainly from
neurons in the raphe magnus, pallidus and obscurus nuclei.
They project as ventral, dorsal and intermediate spinal tracts in
the ventral and lateral funiculi, and terminate respectively in the
ventral horns and laminae I, II and V of the dorsal horns of all
segments, and in the thoracolumbar intermediolateral
sympathetic and sacral parasympathetic preganglionic cell
columns.
27. The dorsal raphe spinal projections function as a pain control
pathway that descends from a mesencephalic pain control centre
located in the periaqueductal grey matter, dorsal raphe and
cuneiform nuclei. The intermediate raphe-spinal projection is
inhibitory and, in part, modulates central sympathetic control of
cardiovascular function. The ventral raphe-spinal system excites
ventral horn cells and could function to enhance motor responses
to nociceptive stimuli.
28.
29.
30.
31.
32. Principally, the mesencephalic serotoninergic raphe system is reciprocally
interconnected rostrally with the limbic system, septum, prefrontal cortex and
hypothalamus. Efferents ascend and form a large ventral and a diminutive dorsal
pathway.
33.
34. Somatic motor control - Some motor neurons send their axons to the reticular
formation nuclei, giving rise to the reticulospinal tracts of the spinal cord. These
tracts play a large role in maintaining tone, balance, and posture, especially during
movement. The reticular formation also relays eye and ear signals to
the cerebellum so that visual, auditory, and vestibular stimuli can be integrated in
motor coordination. Other motor nuclei include gaze centers, which enable the
eyes to track and fixate objects, and central pattern generators, which produce
rhythmic signals to the muscles of breathing and swallowing
35. Habituation – This is a process in which the brain learns to ignore repetitive,
meaningless stimuli w This is a process in which the brain learns to ignore repetitive,
meaningless stimuli while remaining sensitive to others. A good example of this is a
person who can sleep through loud traffic in a large city, but is awakened promptly due
to the sound of an alarm or crying baby. Reticular formation nuclei that modulate activity
of the cerebral cortex are part of the reticular activating systemperson who can sleep
through loud traffic in a large city, but is awakened promptly due to the sound of an alarm
or crying baby. Reticular formation nuclei that modulate activity of the cerebral cortex are
part of the reticular activating system.[2][
HABITUATION
36.
37. MEDIAL COLUMN OF
RETICULARNUCLEI
THE MEDIAL COLUMN OF RETICULAR NUCLEI IS
COMPOSED PREDOMINANTLY OF NEURONES OF
MEDIUM SIZE, ALTHOUGH VERY LARGE NEURONES ARE
FOUND IN SOME REGIONS, AND MOST HAVE
PROCESSES ORIENTATED IN THE TRANSVERSE PLANE.
IN THE LOWER MEDULLA THE COLUMN IS INDISTINCT,
AND IS PERHAPS REPRESENTED BY A THIN LAMINA
LATERAL TO THE RAPHE NUCLEI.
41. Afferent components to the medial reticular nuclear
1.spinoreticular projection
2.spinal trigeminal fibers
3. spinal vestibular fiber
4.spinal cochlear fibres.
42. RETICULOSPINAL TRACT
Pontine(lateral) rticulospinal tract.origin from oral
and
caudal pontine reticular formation
Medullary(medial)reticulospinal tract. Origin from
medullary reticular formation
Terminate in venteral spinal cord
43.
44.
45. Function
1. Integrates information from the motor systems to coordinate
automatic movements of locomotion and posture
2. Facilitates and inhibits voluntary movement; influences
muscle tone
3. Mediates autonomic functions
4. Modulates pain impulses
46. The MRST is responsible for exciting anti-gravity, extensor muscles. The
fibers of this tract arise from the caudal pontine reticular nucleus and the oral
pontine reticular nucleus and project to the lamina VII and lamina VIII of the
spinal cord
The LRST is responsible for inhibiting excitatory axial extensor muscles of
movement. The fibers of this tract arise from the medullary reticular
formation, mostly from the gigantocellular nucleus, and descend the length of
the spinal cord in the anterior part of the lateral column. The tract terminates
in lamina VII mostly with some fibers terminating in lamina IX of the spinal
cord.
47. Lesions to the cortico-reticulospinal system can result in decreased
postural control and reduced selectivity of postural control.
If the excitatory fibres in the reticular formation have a leison this can
result in hypotonia by the loss of descending excitatatory impulses to
the spinal cord. Conversly in the inhibitory fibres are disrupted in the
reticular formation this could result in hypertonia (spasticity) As the
lateral reticulospinal's is involved in inhibition, if this pathway is disruped
it can result in spasticity . In addition due to the lack of descending
inhibition, the medial reticulospinal tract would then maintain spasticity
in the musculatur
48.
49.
50. DECORTICAT POSTURING
• Decorticate posturing is also called decorticate
response, decorticate rigidity, flexor posturing, Patients with
decorticate posturing present with the arms flexed, or bent inward on
the chest, the hands are clenched into fists, and the legs extended
and feet turned inward. A person displaying decorticate posturing in
response to pain gets a score of three in the motor section of
the Glasgow Coma Scale
51.
52. There are two parts to decorticate posturing.
•The first is the disinhibition of the red nucleus with facilitation of
the rubrospinal tract. The rubrospinal tract facilitates motor
neurons in the cervical spinal cord supplying the flexor muscles of
the upper extremities. The rubrospinal tract and medullary
reticulospinal tract biased flexion outweighs the medial and lateral
vestibulospinal and pontine reticulospinal tract biased extension in
the upper extremities.
•The second component of decorticate posturing is the disruption
of the lateral corticospinal tract which facilitates motor neurons in
the lower spinal cord supplying flexor muscles of the lower
extremities. Since the corticospinal tract is interrupted, the pontine
reticulospinal and the medial and lateral vestibulospinal biased
extension tracts greatly overwhelm the medullary reticulospinal
biased flexion tract.
53. The effects on these two tracts
(corticospinal and rubrospinal) by
lesions above the red nucleus is
what leads to the characteristic
flexion posturing of the upper
extremities and extensor posturing
of the lower extremities
54. Decorticate posturing indicates
that there may be damage to
areas including the cerebral
hemispheres, the internal
capsule, and the thalamus. It
may also indicate damage to
the midbrain.
55. DECEREBRATE POSTURE
• Decerebrate posturing is also called decerebrate
response, decerebrate rigidity, or extensor posturing. It describes
the involuntary extension of the upper extremities in response to
external stimuli. In decerebrate posturing, the head is arched back,
the arms are extended by the sides, and the legs are extended. A
hallmark of decerebrate posturing is extended elbows The arms and
legs are extended and rotated internally. The patient is rigid, with the
teeth clenched. The signs can be on just one side of the body or on
both sides, and it may be just in the arms and may be intermittent.
56. A person displaying decerebrate posturing in response to pain gets
a score of two in the motor section of the Glasgow Coma Scale (for
adults)
Decerebrate posturing indicates brain stem damage, specifically
damage below the level of the red nucleus It is exhibited by people
with lesions or compression in the midbrain and lesions in
the cerebellum Decerebrate posturing is commonly seen
in pontine strokes.
57.
58. . Spinoreticular fibres
part of the anterolateral system, arise from neurones in the
intermediate grey matter of the spinal cord.
They decussate in the ventral white commissure, ascend
in the ventrolateral funiculus,
terminate not only at all levels of the medial column of
reticular nuclei but also in the intralaminar nuclei of the
thalamus.
59.
60. . Information is sent from there to the intradmedian
nucleus of the thalamic intralaminar nuclei. The
thalamic intralaminar nuclei project diffusely to entire
cerebral cortex where pain reaches conscious level
and promotes behavioral arousal.It is believed that
spinoreticular tract projects to neurons having a large
receptive fields that may cover wide areas of the body
and play a role in the memory and in the affective
(emotional) component of pain
61. Efferents from the medial column of reticular nuclei
project through a multisynaptic pathway within the
column to the thalamus.
Areas of maximal termination of spinoreticular fibres also
project directly to the intralaminar thalamic nuclei.
The multisynaptic pathway is integrated into the lateral
column of reticular nuclei with cholinergic neurones in
the lateral pontine tegmentum.
The intralaminar thalamic nuclei project directly to the
striatum and neocortex.
62.
63. LATERAL COLUMN OF RETICULAR
FORMATION NUCLEOS
MIDBRAIN
CUNEIFORM AND SUBCONEIFORM
NUCLOS
PONS
RETICULLARIS PARVOCELLULARIS
PARABRACHIAL PEDUNCULOPONTINE
LOCUS COERULEUS
MEDULLA
RETICULLARIS PARVOCELLULARIS
RETICULLARIS LATERALIS
64. The lateral column of reticular nuclei contains six nuclear groups, which
include the parvocellular reticular area; superficial ventrolateral reticular area;
lateral pontine tegmental noradrenergic cell groups A1, A2 and A4 to A7 (A3
is absent in primates); adrenergic cell groups C1 and C2; and cholinergic cell
groups Ch5 and Ch6. The column descends through the lower two-thirds of
the lateral pontine tegmentum and upper medulla, where it lies between the
gigantocellular nucleus medially and the sensory trigeminal nuclei laterally. It
continues caudally and expands to form most of the reticular formation
lateral to the raphe nuclei. It abuts the superficial ventrolateral reticular area,
nucleus solitarius, nucleus ambiguus and vagal nucleus, where it contains the
adrenergic cell group C2 and the noradrenergic group A2.
65.
66. The lateral paragigantocellular nucleus lies at the rostral pole of the
diffuse superficial ventrolateral reticular area (at the level of the facial
nucleus). The zone extends caudally as the nucleus retroambiguus and
descends into the spinal cord. It contains noradrenergic cell groups A1, A2,
A4 and A5 and the adrenergic cell group C1.
The ventrolateral reticular area is involved in cardiovascular, respiratory, vasoreceptor
and chemoreceptor reflexes and in the modulation of nociception.
The A2 or noradrenergic dorsal medullary cell group lies in the nucleus of the tractus
solitarius,vagal nucleus and adjoining parvocellular reticular area
Adrenergic group C1 lies rostral to the A2 cell group. Noradrenergic cell group A4
extends into the lateral pontine tegmentum, along the subependymal surface of the
superior Cerebellar peduncle
Noradrenergic group A5 forms part of the paragigantocellular
nucleus in the caudolateral pontine tegmentum
67.
68. The lateral pontine tegmental reticular grey matter is related to the
superior cerebellar peduncle and forms the medial and lateral
parabrachial nuclei and the ventral Kölliker-Fuse nucleus, a pneumotaxic
centre.
The locus coeruleus (noradrenergic cell group A6), area subcoeruleus,
noradrenergic cell group A7 and cholinergic group Ch5 in the
pedunculopontine tegmental
nucleus are all located in the lateral pontine and mesencephalic
tegmental reticular zones.
69.
70. Cell group A6 contains all the noradrenergic cells in
the central region of the locus coeruleus. Group A6
has ventral (nucleus subcoeruleus), rostral and
caudolateral extensions; the last merges with the A4
group.
The locus coeruleus probably functions as an
attention centre,focusing neural functions on
prevailing needs.
The noradrenergic A7 group occupies the
rostroventral part of the pontine tegmentum
The A7, A5, A1 complex is also connected
by noradrenergic cell clusters with group A2
caudally and with group A6 rostrally.
71.
72. The A5 and A7 groups lie mainly within the medial
parabrachial
and Kölliker-Fuse nuclei.
Reticular neurones in the lateral pontine tegmental
reticular area, like those of the ventrolateral zone,
function to regulate respiratory,
cardiovascular and gastrointestinal activity.
Two micturition centres are located in the dorsomedial
and ventrolateral parts of the lateral pontinetegmentum.
73. In the human brain, the parabrachial area, also known as
the parabrachial complex and parabrachial nucleus, is a
horseshoe-shaped strip of gray matter comprising
the subparabrachial nucleus(Kölliker-Fuse nucleuS)
the lateral parabrachial nucleus
the medial parabrachial nucleus.
It is located at the junction of the midbrain and Pons in
the lateral reticular formation, rostral to the parvocellular
reticular nucleus near the superior cerebellar peduncle
PARABRACHIAL COMPLEX
74. The respiratory centers are divided into four major groups:
medulla
dorsal respiratory group
ventral respiratory group.
pons
pneumotaxic center also known as the pontine respiratory
group
apneustic center.
75.
76. Inspiratory center (Dorsal respiratory group)
•Location: Dorsal portion of medulla
•Nucleus: Nucleus tractus solitaries
Expiratory center (Ventral respiratory group)
•Location: Antero- lateral part of medulla, about 5 mm
anterior and lateral to dorsal respiratory group
•Nucleus: Nucleus ambiguus and nucleus retro
ambiguus.
•Function: It generally causes expiration but can cause
either expiration or inspiration depending upon which
neuron in the group is stimulated. It sends inhibitory
impulse to the apneustic center
77. Pneumotaxic center
•Location: Pons (upper part )
•Nucleus: Nucleus parabrachialis
•Function: It controls both rate and pattern of breathing. Limit
inspiration.
Apneustic center
•Location: Pons (lower part)
•Functions:
a.It discharges stimulatory impulse to the inspiratory center causing
inspiration.
b.It receives inhibitory impulse from pneumotaxic center and from
stretch receptor of lung.
c.It discharges inhibitory impulse to expiratory center
78.
79.
80. The automatic central control of
respiration may be influenced and
temporarily overridden by volitional
control from the cerebral cortex
(motor area , area 4,6) for a variety of
activities, such as speech, singing,
laughing, intentional and
psychogenic alterations of
respiration, and breath holding
81.
82.
83.
84.
85. Central chemoreceptors
Central chemoreceptors, located
primarily within the ventrolateral surface
of medulla, respond to changes in brain
extracellular fluid [H1] concentration.
Other receptors have been recently
identified in the brainstem,
hypothalamus, and the cerebellum.
These receptors are effectively CO2
receptors because central [H1]
concentrations are directly dependent on
central PCO2 levels.
86. Peripheral chemoreceptors include the carotid bodies
and the aortic bodies.
The carotid bodies, located bilaterally at the bifurcation
of the internal and external carotid arteries, are the
primary peripheral monitors.
They are highly vascular structures that monitor the
status of blood about to be delivered to the brain and
provide afferent input to the medulla through the 9th
cranial nerve.
The carotid bodies respond mainly to PaO2, but also to
changes in PaCO2 and pH.
PERIPHERAL
CHEMORECEPTORS
87. Descending motoneurons include two anatomically
separate groups:
• The corticospinal and corticobulbar tracts for the
volitional control of respiration and
• The reticulospinal tracts for the automatic control of
respiration .
88.
89.
90.
91.
92. The Pontine micturition center (PMC, also known
as Barrington's nucleus) is a collection of neuronal cell
bodies located in the rostral pons in the brainstem involved in
the supraspinal regulation of micturition. When activated, the
PMC relaxes the urethral sphincter allowing for micturition to
occur. The PMC coordinates with other brain centers,
including the medial frontal cortex, insular
cortex, hypothalamus and periaqueductal gray (PAG). The
PAG acts as a relay station for ascending bladder information
from the spinal cord and incoming signals from higher brain
areas.
MICTURATION CENTER
93. •Normal voiding occurs in response to afferent signals of the bladder filling, and it is
controlled by nervous system of the brain and spinal cord.
•CNS and PNS coordinate the activity of the detrusor smooth muscle and urethral
sphincter muscle.
•The S2–S4 spinal cord constitute primary parasympathetic micturition center that
innervate the bladder as well as the distal urethral sphincter (striated sphincter).
•Above the sacral segments, the thoracolumbar segments (T11-L2) provide the
sympathetic outflow from the spinal cord to the bladder and the proximal urethral
sphincter.
•Above the spinal cord is an important control center in the pons where it directly
excites bladder neurons and inhibits the urethral sphincter, thus resulting
coordination of the bladder contraction and sphincter relaxation at the same time to
empty the urine.
•The cerebral cortex appears to be involved in inhibiting lower centers of
micturition.
•Primary neurologic control of the bladder and urethral sphincters depends on
multiple levels of the nervous system, especially the sacral segments and the pons
94. Peripheral innervation:
The lower urinary tract is innervated by three
principal sets of peripheral nerves involving
the parasympathetic, sympathetic, and somatic
nervous systems from 3 major nerves, namely
the pelvic, hypogastric and pudendal nerves,
respectively.
These nerves contain afferent (sensory) as
well as efferent (motor) axons.
Parasympathetic and sympathetic nervous
systems form pelvic plexus at the lateral side
of the rectum before reaching bladder and
sphincter.
95. oParasympathetic nerves:
emerge from the S2-4 (parasympathetic
nucleus; intermediolateral column of gray
matter)
exciting the bladder and relax the urethra
96. oSympathetic pathways:
originate from the T11-L2 (sympathetic nucleus;
intermediolateral column of graymatter)
inhibiting the bladder body and excite the bladder
base and proximal urethral sphincter
97. oSacral somatic pathways:
emerge from the S2-4 (Onuf’s nucleus; ventral
horn)
form pudendal nerve, providing an innervation to
the striated urethral sphincter.
Pudendal nerves from S2-4 excite the distal striated
urethral sphincter.
98.
99. Sympathetic postganglionic nerves — for
example, the hypogastric nerve — release
noradrenaline, which activates β adrenergic
inhibitory receptors in the detrusor muscle
to relax the bladder, α-adrenergic
excitatory receptors in the urethra and the
bladder neck, and α- and β-adrenergic
receptors in bladder ganglia
100.
101. The micturition reflex is a bladder-to-bladder contraction reflex for which the
reflex center is located in the rostral pontine tegmentum (pontine micturition
center: PMC). There are two afferent pathways from the bladder to the brain. One
is the dorsal system and the other is the spinothalamic tract. Afferents to the PMC
ascend in the spinotegmental tract, which run through the lateral funiculus of the
spinal cord. The efferent pathway from the PMC also runs through the lateral
funiculus of the spinal cord to inhibit the thoracolumbar sympathetic nucleus and
the sacral pudendal nerve nucleus,
102. There are two centers that inhibit micturition in the
pons, which are the pontine urine storage center and
the rostral pontine reticular formation. In the
lumbosacral cord, excitatory glutamatergic and
inhibitory glycinergic/GABAergic neurons influence
both the afferent and efferent limbs of the micturition
reflex. The activity of these neurons is affected by the
pontine activity. There are various excitatory and
inhibitory areas co-existing in the brain, but the brain
has an overall inhibitory effect on micturition, and thus
maintains continence. For micturition to occur, the
cerebrum must abate its inhibitory influence on the
PMC
103. PONTINE MICTURITION CENTERS (Barrington's nucleus):
– pontomesencephalic reticular formation micturition center
(located in the locus ceruleus, pontomesencephalic gray
matter, and nucleus tegmentolateralis dorsalis). – collection of
cell bodies located in the rostral pons in the brainstem
involved in the supraspinal regulation of micturition (urination).
– The PMC makes connections with other brain centers to
control micturition, including the medial frontal cortex, insular
cortex, hypothalamus and periaqueductal gray (PAG). – The
PAG in particular acts a relay station for ascending bladder
information from the spinal cord and incoming signals from
higher brain areas.
104.
105.
106. Storage reflexes
During filling, there is low-level activity from bladder
afferent fibers signaling distension via the pelvic nerve,
which in turn stimulates sympathetic outflow to the
bladder neck and wall via the hypogastric nerve. This
sympathetic stimulation relaxes the detrusor and
contracts the bladder neck at the internal sphincter.
Afferent pelvic nerve impulses also stimulate the
pudendal (somatic) outflow to the external sphincter
causing contraction and maintenance of continence
107. Voiding reflexes.
Upon initiation of micturition, there is high-intensity
afferent activity signaling wall tension, which activates
the brainstem pontine micturition center.
Spinobulbospinal reflex can be seen as an ascending
signal from afferent pelvic nerve stimulation (left side),
which passes through the periaqueductal gray matter
before reaching the pontine micturition center and
descending to elicit parasympathetic contraction of the
detrusor, and somatic relaxation via the pudendal nerve
108.
109. . • The somatic storage reflex or the pelvic-to-pudendal or
guarding reflex is initiated when one laughs, sneezes, or
coughs, which causes increased bladder pressure.
Glutamate is the primary excitatory transmitter for the
reflex. Glutamate activates NMDA and AMPA receptors
which produce action potentials. These action potentials
activate the release of acetylcholine causing the
rhabdosphincter muscle fibers to contract.
110. HIGHER CENTERS • CORTICAL CENTERS
Situated in • Medial frontal lobe • Cingulate gyrus • Corpus
collosum • cortical input is inhibitory on micturition reflexes.
Subcortical centers: – thalamic nuclei – limbic system, –
Red nucleus – Substantia nigra – Hypothalamus –
Subthalamic nucleus. • Cerebellum : – anterior vermis of
the cerebellum – fastigial nucleus are concerned with
micturition
111.
112.
113. SPINAL REFLEX ARC •
AFFERENT ARC: – Sensation of stretch arising from
bladder wall travels through the parasympathetic nerves
to the center for micturition • DETRUSOR CENTER OR
SACRAL PARASYMPATHETIC NUCLEUS – sacral
segments S2,S4 of the spinal cord.
•
EFFERENT ARC (PARASYMPATHATIC) – travels
through the pelvic nerves to the pelvic plexus; short
postganglionic fibers travel from the plexus to the detrusor
muscle
114. Parasympathetic postganglionic nerves release both
cholinergic (acetylcholine, ACh) and non-adrenergic,
non-cholinergic transmitters. Cholinergic transmission
is the major excitatory mechanism in the human
bladder . It results in detrusor contraction and
consequent urinary flow and is mediated principally
by the M3 muscarinic receptor, although bladder
smooth muscle also expresses M2 receptors5.
Muscarinic receptors are also present on
parasympathetic nerve terminals at the neuromuscular
junction and in the parasympathetic ganglia .
115. Somatic cholinergic motor nerves that supply
the striated muscles of the external urethral
sphincter arise in S2–S4 motor neurons in
Onuf's nucleus and reach the periphery through
the pudendal nerves . A medially placed motor
nucleus at the same spinal level supplies axons
that innervate the pelvic floor musculature
116. The somatic motor neurons that
innervate the external urethral sphincter
are located in the ventral horn (lamina
IX) in Onuf's nucleus, have a similar
arrangement of transverse dendrites
and have an extensive system of
longitudinal dendrites that travel within
Onuf's nucleus
117. In the brain, many neuron populations are involved in
the control of the bladder, the urethra and the urethral
sphincter. Some, such as the serotonergic neurons of
the medullary raphe nuclei, the noradrenergic
neurons of the locus coeruleus and the
noradrenergic A5 cell group in the brain stem, are
non-specific ‘level-setting’ mechanisms with diffuse
spinal projections . Others are specific for
micturition: these include the neurons of Barrington's
nucleus (also called the pontine micturition centre
(PMC)) and those of the periaqueductal grey (PAG),
cell groups in the caudal and preoptic hypothalamus,
and the neurons of several parts of the cerebral
118. The neural pathways that control lower-urinary-
tract function are organized as simple on–off
switching circuits that maintain a reciprocal
relationship between the urinary bladder and
the urethral outlet. Storage reflexes are
activated during bladder filling and are
organized primarily in the spinal cord, whereas
voiding is mediated by reflex mechanisms that
are organized in the brain
119. Micturition Reflex
Referring again to Figure 26–7, one can see that as the
bladder fills, many superimposed micturition contraction
begin to appear, as shown by the dashed spikes.They
are the result of a stretch reflex initiated by sensory
stretch receptors in the bladder wall, especially by the
receptors in the posterior urethra when this area begins
to fill with urine at the higher bladder pressures. Sensory
signals from the bladder stretch receptors are conducted
to the sacral segments of the cord through the pelvic
nerves and then reflexively back
again to the bladder through the parasympathetic nerve
fibers by way of these same nerves.
120.
121.
122. Once a micturition reflex begins, it is “self-
regenerative.”
That is, initial contraction of the bladder activates
the stretch receptors to cause a greater increase
in sensory impulses to the bladder and posterior
urethra, which causes a further increase in reflex
contraction of the bladder; thus, the cycle is repeated
again and again until the bladder has reached a strong
degree of contraction
. Then, after a few seconds to
more than a minute, the self-regenerative reflex begins
to fatigue and the regenerative cycle of the micturition
reflex ceases, permitting the bladder to relax.
123. When the bladder is only partially filled, these
micturition
contractions usually relax spontaneously after
a fraction of a minute, the detrusor muscles stop
contracting,
and pressure falls back to the baseline. As the
bladder continues to fill, the micturition reflexes
become more frequent and cause greater contractions
of the detrusor muscle.
124. Facilitation or Inhibition of Micturition
by the Brain
The micturition reflex is a completely autonomic
spinal cord reflex, but it can be inhibited or facilitated
by centers in the brain.
These centers include
strong facilitative and inhibitory centers in the
brain stem, located mainly in the pons, and
several centers located in the cerebral cortex that
are mainly inhibitory but can become excitatory.
125. The micturition reflex is the basic cause of micturition, but
the higher centers normally exert final control of
micturition as follows:
1. The higher centers keep the micturition reflex partially
inhibited, except when micturition is desired.
2. The higher centers can prevent micturition, even if the
micturition reflex occurs, by continual tonic contraction of
the external bladder sphincter until a convenient time
presents itself.
3. When it is time to urinate, the cortical centers can
facilitate the sacral micturition centers to help initiate a
micturition reflex and at the same time inhibit the external
urinary sphincter so that urination can occur.
126. Voluntary urination is usually initiated in the following
way: First, a person voluntarily contracts his or her
abdominal muscles, which increases the pressure in
the bladder and allows extra urine to enter the
bladder neck and posterior urethra under pressure,
thus stretching their walls. This stimulates the stretch
receptors, which excites the micturition reflex and
simultaneously inhibits the external urethral
sphincter.
Ordinarily, all the urine will be emptied, with rarely
more than 5 to 10 milliliters left in the bladder.
127.
128.
129.
130.
131. Abnormalities of Micturition
Atonic Bladder Caused by Destruction of Sensory Nerve Fibers.
Micturition reflex contraction cannot occur if the
sensory nerve fibers from the bladder to the spinal cord
are destroyed, thereby preventing transmission of
stretch signals from the bladder.When this
happens, a
person loses bladder control, despite intact
efferent
fibers from the cord to the bladder and despite
intact
neurogenic connections within the brain. Instead
of
emptying periodically, the bladder fills to capacity
and overflows a few drops at a time through the
132. A common cause of atonic bladder is
crush injury to the sacral region of the
spinal cord. Certain diseases can also
cause damage to the dorsal root nerve
fibers that enter the spinal cord. For
example, syphilis can cause
constrictive fibrosis around the dorsal
root nerve fibers, destroying them. This
condition is called tabes dorsalis, and
the resulting bladder condition is called
tabetic bladder.
133. Automatic Bladder Caused by Spinal Cord Damage Above the Sacral
Region. If the spinal cord is damaged above the
sacral region but the sacral cord segments are still intact, typical
micturition reflexes can still occur. However, they are no longer
controlled by the brain. During the first few days to several weeks after
the damage to the
cord has occurred, the micturition reflexes are suppressed
because of the state of “spinal shock” caused by the sudden loss of
facilitative impulses from the brain
stem and cerebrum. However, if the bladder is emptied periodically by
catheterization to prevent bladder injury caused by overstretching of
the bladder, the excitability of the micturition reflex gradually increases
until typical micturition reflexes return; then, periodic (but
unannounced) bladder emptying occurs. Some patients can still
control urination in this condition by stimulating the skin (scratching or
134. Uninhibited Neurogenic Bladder Caused by Lack
of Inhibitory Signals from the Brain. Another
abnormality of micturition is the so-called
uninhibited neurogenic bladder,
which results in frequent and relatively
uncontrolled micturition.This condition derives
from partial damage in the spinal cord or the brain
stem that interrupts most
of the inhibitory signals.Therefore, facilitative
impulses passing continually down the cord keep
the sacral centers so excitable that even a small
quantity of urine elicits an uncontrollable
micturition reflex, thereby promoting frequent
135. Spinal Shock
After SCI, initially there is flaccid muscle paralysis and absent
somatic activity, as well as suppressed autonomic activity below
the area of th lesion. The bladder is acontractile and areflexic.
The bladder neck is generally closed and competent. Sphincter ton will be
mainteined Because of the preservation of external
sphincter tone, urinary incontinence is usually secondaty to poor
emptying and overflow incontinence. Patients will have urinaty
retention during the period of spinal shock and require either
intermittent or continuous catheterization to empty the bladder.
Involuntary voiding between intermittent catheterizations indicates
the return of reflex bladder activity. Spinal shock generally
lasts 6 to 12 weeks but may continue as long as 1 to 2 month years.
SPINAL SHOCK
137. The locus coeruleus is located in the posterior area of the
rostral pons in the lateral floor of the fourth ventricle. It is
composed of mostly medium-size neurons. Melanin granules
inside the neurons of the LC contribute to its blue color. Thus, it
is also known as the nucleus pigmentosus pontis, meaning
"heavily pigmented nucleus of the pons.
138. The locus coeruleus (LC) is the major noradrenergic nucleus of the brain,
giving rise to fibres innervating extensive areas throughout the neuraxis.
Recent advances in neuroscience have resulted in the unravelling of the
neuronal circuits controlling a number of physiological functions in which the
LC plays a central role. Two such functions are the regulation of arousal and
autonomic activity, which are inseparably linked largely via the involvement of
the LC. The LC is a major wakefulness-promoting nucleus, resulting from
dense excitatory projections to the majority of the cerebral cortex, cholinergic
neurones of the basal forebrain, cortically-projecting neurones of the thalamus,
serotoninergic neurones of the dorsal raphe and cholinergic neurones of the
pedunculopontine and laterodorsal tegmental nucleus, and substantial inhibitory
projections to sleep-promoting GABAergic neurones of the basal forebrain and
ventrolateral preoptic area. Activation of the LC thus results in the
enhancement of alertness through the innervation of these varied nuclei
139.
140. The importance of the LC in controlling autonomic function
results from both direct projections to the spinal cord and
projections to autonomic nuclei including the dorsal motor
nucleus of the vagus, the nucleus ambiguus, the
rostroventrolateral medulla, the Edinger-Westphal nucleus,
the caudal raphe, the salivatory nuclei, the paraventricular
nucleus, and the amygdala. LC activation produces an
increase in sympathetic activity and a decrease in
parasympathetic activity via these projections. Alterations
in LC activity therefore result in complex patterns of
neuronal activity throughout the brain, observed as
changes in measures of arousal and autonomic function
141.
142. Noradrenergic receptors on follower cells receiving an afferent input
from the LC can be generally classified as α1-, α2- or β-adrenoceptors.
Activation of α1-adrenoceptors by noradrenaline generally leads to
excitation of the follower cells and there is some evidence that β-
adrenoceptors are also excitatory . In contrast, activation of α2-
adrenoceptors leads to inhibition of the follower cells , and also of the
noradrenergic neurones themselves (“autoreceptors”). The
consequences of autoreceptors activation can be detected as changes in
the firing rate of LC neurones and in the release of noradrenaline. α2 –
Adrenoceptors are widely distributed in the brain and there are
regional differences in their role in modulating noradrenaline releas
143.
144. The reticular activating system (RAS),
or extrathalamic control modulatory
system, is a set of connected nuclei in
the brains of vertebrates that is responsible
for regulating wakefulness and sleep-wake
transitions. As its name implies, its most
influential component is the reticular
formation
RETICULAR ACTIVAYING SYSTEM
145. Anatomical components
The RAS is composed of several neuronal circuits connecting the brainstem to
the cortex. These pathways originate in the upper brainstem reticular core and
project through synaptic relays in the rostral intralaminar and thalamic nuclei to
the cerebral cortex As a result, individuals with bilateral lesions of thalamic
intralaminar nuclei are lethargic or somnolent.Several areas traditionally
included in the RAS are:
Midbrain Reticular Formation
Mesencephalic Nucleus (in Midbrain)
Thalamic Intralaminar nucleus (centromedian nucleus)
Dorsal Hypothalamus
Tegmentum
The RAS consists of evolutionarily ancient areas of the brain, which are crucial
to survival and protected during adverse periods. As a result, the RAS still
functions during inhibitory