This document provides an overview of the nervous system, including its anatomical structures and organization. It describes the main parts of the brain and spinal cord, such as the cerebrum, thalamus, hypothalamus, brain stem, and spinal cord. It also discusses neurons, nerve cells, dendrites, axons and synapses. Additionally, it covers the sensory, motor and autonomic nervous systems, and functions like pain, touch, reflexes, senses and sleep.
The document discusses the nervous system, including the brain, spinal cord, and nerves. It describes the main parts of the brain - the cerebrum, cerebellum, and brain stem. It explains the functions of these parts and how sensory, motor, and mixed nerves transfer messages between the brain and other parts of the body for both voluntary and involuntary actions.
The document summarizes the structure and function of the nervous system. It is divided into the central nervous system (CNS), which includes the brain and spinal cord, and the peripheral nervous system (PNS). The CNS controls and coordinates body activities, while the PNS connects the CNS to other parts of the body. Within the nervous system are neurons, which transmit signals, and the brain, spinal cord, nerves, and ganglia through which signals travel from the CNS to the rest of the body and back.
The nervous system is divided into the central nervous system (CNS) and peripheral nervous system (PNS). The CNS contains the brain and spinal cord, while the PNS contains nerves that connect the CNS to sensory organs and effector organs. The basic functional unit of the nervous system is the neuron, which transmits electrochemical signals. The nervous system also contains neuroglial cells that provide support to neurons. Sensory neurons carry signals to the CNS, motor neurons carry signals from the CNS, and interneurons connect sensory and motor neurons within the CNS.
Hypnosis is an induced altered state of consciousness characterized by heightened focus and suggestibility. It can be self-induced through activities like daydreaming or meditation, or induced by a hypnotist through relaxation and focused attention techniques. While some myths exist around hypnosis involving mind control, research shows subjects maintain voluntary control and hypnosis simply involves using imagination and suggestion to influence perceptions, sensations, and behaviors. Hypnosis has various therapeutic and medical applications and any willing person of average intelligence can experience it, though some are more suggestible than others. Risks are small but safeguards like pre-hypnosis screening are recommended.
Nyaya philosophy was founded by the sage Gotama around 600 BC. It is primarily concerned with epistemology and establishing valid means of obtaining knowledge. Nyaya divides reality into 16 categories or "padarthas" including the sources of knowledge (praman), objects of knowledge (prameya), doubt (samsaya), and inference (anumana). The sources of valid knowledge are direct perception, inference, comparison, and testimony, while doubt, faulty cognition, and hypothetical arguments are not reliable means of knowledge.
This document provides an introduction to cognitive neurophysiology. It discusses the evolution of understanding of cognition from ancient times to modern neuroscience. Key topics covered include the historical understanding of the brain and mind, early studies of brain anatomy and localization of function, development of brain mapping techniques like CT, MRI, fMRI and PET scans, as well as cellular-level discoveries like neurons and neural networks. The objectives of studying cognitive neurophysiology are outlined, such as understanding the functional and structural organization of the nervous system, sensory and motor processing, consciousness, higher cognitive functions, brain development and genetics, and recent advances in the field.
Reiki is a technique for stress reduction and relaxation that also promotes healing. It involves channeling universal life force energy through the palms of the practitioner to the recipient. A Reiki practitioner receives attunement to open their energy channels. There are different levels of Reiki training and techniques like hand positions, aura scanning, and distance healing. Reiki is believed to help balance the biofield and energy centers of the body.
This document summarizes key aspects of voluntary motor control and the neural systems involved. It discusses how the basal ganglia, cerebellum, and motor cortex work together to plan and execute movements. The spinal cord and motor neurons are also covered, as well as mechanisms of muscle contraction and sensory feedback systems that provide input to modulate movement.
The document discusses the nervous system, including the brain, spinal cord, and nerves. It describes the main parts of the brain - the cerebrum, cerebellum, and brain stem. It explains the functions of these parts and how sensory, motor, and mixed nerves transfer messages between the brain and other parts of the body for both voluntary and involuntary actions.
The document summarizes the structure and function of the nervous system. It is divided into the central nervous system (CNS), which includes the brain and spinal cord, and the peripheral nervous system (PNS). The CNS controls and coordinates body activities, while the PNS connects the CNS to other parts of the body. Within the nervous system are neurons, which transmit signals, and the brain, spinal cord, nerves, and ganglia through which signals travel from the CNS to the rest of the body and back.
The nervous system is divided into the central nervous system (CNS) and peripheral nervous system (PNS). The CNS contains the brain and spinal cord, while the PNS contains nerves that connect the CNS to sensory organs and effector organs. The basic functional unit of the nervous system is the neuron, which transmits electrochemical signals. The nervous system also contains neuroglial cells that provide support to neurons. Sensory neurons carry signals to the CNS, motor neurons carry signals from the CNS, and interneurons connect sensory and motor neurons within the CNS.
Hypnosis is an induced altered state of consciousness characterized by heightened focus and suggestibility. It can be self-induced through activities like daydreaming or meditation, or induced by a hypnotist through relaxation and focused attention techniques. While some myths exist around hypnosis involving mind control, research shows subjects maintain voluntary control and hypnosis simply involves using imagination and suggestion to influence perceptions, sensations, and behaviors. Hypnosis has various therapeutic and medical applications and any willing person of average intelligence can experience it, though some are more suggestible than others. Risks are small but safeguards like pre-hypnosis screening are recommended.
Nyaya philosophy was founded by the sage Gotama around 600 BC. It is primarily concerned with epistemology and establishing valid means of obtaining knowledge. Nyaya divides reality into 16 categories or "padarthas" including the sources of knowledge (praman), objects of knowledge (prameya), doubt (samsaya), and inference (anumana). The sources of valid knowledge are direct perception, inference, comparison, and testimony, while doubt, faulty cognition, and hypothetical arguments are not reliable means of knowledge.
This document provides an introduction to cognitive neurophysiology. It discusses the evolution of understanding of cognition from ancient times to modern neuroscience. Key topics covered include the historical understanding of the brain and mind, early studies of brain anatomy and localization of function, development of brain mapping techniques like CT, MRI, fMRI and PET scans, as well as cellular-level discoveries like neurons and neural networks. The objectives of studying cognitive neurophysiology are outlined, such as understanding the functional and structural organization of the nervous system, sensory and motor processing, consciousness, higher cognitive functions, brain development and genetics, and recent advances in the field.
Reiki is a technique for stress reduction and relaxation that also promotes healing. It involves channeling universal life force energy through the palms of the practitioner to the recipient. A Reiki practitioner receives attunement to open their energy channels. There are different levels of Reiki training and techniques like hand positions, aura scanning, and distance healing. Reiki is believed to help balance the biofield and energy centers of the body.
This document summarizes key aspects of voluntary motor control and the neural systems involved. It discusses how the basal ganglia, cerebellum, and motor cortex work together to plan and execute movements. The spinal cord and motor neurons are also covered, as well as mechanisms of muscle contraction and sensory feedback systems that provide input to modulate movement.
The document summarizes the nervous system and chemical coordination system in three parts:
1. The central nervous system includes the brain and spinal cord. The brain is made up of the forebrain, midbrain, and hindbrain. The spinal cord runs through the vertebral column and contains grey and white matter.
2. The peripheral nervous system includes ganglia and nerves that connect the central nervous system to other parts of the body. There are motor and sensory neurons that carry signals between the central nervous system and other body systems.
3. The chemical coordination system includes the endocrine system made up of endocrine glands that secrete hormones to regulate processes like growth, metabolism, and reproduction.
The document summarizes the main components and functions of the human nervous system. It describes the central nervous system including the brain and spinal cord. It also describes the peripheral nervous system including cranial nerves and spinal nerves. Finally, it discusses the different types of neurons, their functions, and how they transmit signals in the body.
This document summarizes the structure and function of the human nervous system. It describes the basic unit of the nervous system, the neuron, including its cell body, dendrites, and axon. It explains how axons are myelinated and the role of nodes of Ranvier in nerve signal transmission. It then discusses the synapse, reflex arc, and the central and peripheral nervous systems. Within the central nervous system it outlines the main functions of the brain regions including the cerebrum, cerebellum, and medulla oblongata. It concludes by describing the sympathetic and parasympathetic divisions of the autonomic nervous system and some of their roles in stress response and relaxation.
nervous system ppt pptx anatomy system of nervesPhebeLois1
The nervous system has two main divisions - the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS is made up of the brain and spinal cord, which act as integrative and control centers. The PNS includes nerves that connect the CNS to the rest of the body and transmit sensory information to the CNS and motor commands from the CNS. Neurons are the basic functional units and come in sensory, motor, and interneuron types. Supporting glial cells insulate and protect neurons. The nervous system uses electrical and chemical signals to sense the environment, integrate information, and coordinate responses via pathways like ascending and descending tracts in the spinal cord and reflex arcs.
This document provides an overview of the nervous system, including its central and peripheral components. It describes the main cell types - neurons and glial cells. It discusses the key parts of neurons - dendrites, axons, axon hillock. It outlines the main types of neurons and glial cells in both the central and peripheral nervous systems. It provides details on how neurons communicate at synapses and how glial cells support neuronal function.
This document provides an overview of the nervous system, including its main components and functions. It discusses the peripheral nervous system, spinal cord, and central nervous system. It describes the morphological and functional subdivisions of the nervous system. Key topics covered include the embryonic origins and histological composition of nervous system structures. Reflex arcs and the organization of the spinal cord are also summarized.
The central nervous system is protected by three meningeal membranes and contains interconnected ventricles that circulate cerebrospinal fluid. The spinal cord extends from the foramen magnum to the lumbar vertebrae and functions as a center for spinal reflexes and to conduct nerve impulses. The brain controls muscular movements, regulates organs, interprets sensations, stores memories, and determines personality. It contains structures like the cerebrum, cerebellum, and brainstem. The cerebrum is divided into lobes and regions that control motor functions, sensory interpretation, memory, reasoning, and more.
The document provides an overview of the nervous system, including key structures and functions. It discusses the meninges surrounding the central nervous system, ventricles within the brain, cerebrospinal fluid, spinal cord tracts and reflex arcs. It also summarizes the major parts and lobes of the brain, cerebral cortex functions, and the peripheral and autonomic nervous systems.
Lecture notes and diagrams to help high school anatomy and physiology students learn the general functions of the nervous system and types of glial support nerve cells, types of neurons and anatomy of typical neurons.
The nervous system can be divided into the central nervous system (CNS) and peripheral nervous system (PNS). The CNS consists of the brain and spinal cord and is responsible for integrating sensory information and coordinating motor commands. The PNS has two parts - the cerebrospinal part made up of cranial and spinal nerves, and the autonomic nervous system. There are two main cell types in the nervous system - neurons, which transmit signals, and neuroglia, which provide support and insulation. The autonomic nervous system has two divisions - the parasympathetic and sympathetic systems, which work in opposition to activate "rest and digest" and "fight or flight" responses respectively.
The document summarizes key aspects of the central nervous system. It describes the main parts and functions of the brain and spinal cord, including the meninges, ventricles, cerebrospinal fluid, spinal cord structure, brain lobes and areas, diencephalon, limbic system, brain stem, reticular formation, and cerebellum. It also discusses reflexes, motor and sensory areas, memory, sleep, and left and right hemisphere dominance.
The nervous system is divided into the central nervous system (CNS) and peripheral nervous system (PNS). The CNS contains the brain and spinal cord for integrating and controlling signals, while the PNS uses nerves to connect the CNS to the rest of the body. Neurons are the basic functional units that transmit signals via electrical impulses. Supporting glial cells insulate neurons and provide nutrients. Sensory neurons carry signals to the CNS, while motor neurons carry signals from the CNS to muscles and glands. Reflexes are rapid, involuntary responses mediated by neural pathways and occurring without conscious thought.
The document discusses the structure and function of the nervous system. It describes the three basic functions of the nervous system as sensory, integrative, and motor. It then explains the divisions of the nervous system including the central nervous system (CNS) which contains the brain and spinal cord, and the peripheral nervous system (PNS) which contains nerves that connect the CNS to sensory receptors and effectors. Within the PNS it describes the somatic, autonomic, and enteric nervous systems. It also discusses the basic cell types of neural tissue including neurons and neuroglia, and provides diagrams of neuron structure and function.
The document discusses the structure and function of the nervous system. It describes the three basic functions of the nervous system as sensory, integrative, and motor. It then explains the divisions of the nervous system including the central nervous system (CNS) which contains the brain and spinal cord, and the peripheral nervous system (PNS) which contains nerves that connect the CNS to sensory receptors and effectors. Within the PNS it describes the somatic, autonomic, and enteric nervous systems. It also discusses the basic cell types of neural tissue including neurons and neuroglia, and provides diagrams of neuron structure and function.
The document summarizes the key functions and components of the human nervous system. It discusses how the nervous system allows for communication and coordination within the body through the central nervous system (brain and spinal cord) and peripheral nervous system (nerves connecting to muscles and organs). It also describes the basic unit (neuron), divisions (central vs peripheral), and roles of the nervous system in sensation, voluntary control, and involuntary processes.
This document outlines key concepts related to the nervous system. It defines neurons and their parts, and describes how nerve impulses are transmitted. It explains the structure and function of the central nervous system, including the brain regions and spinal cord. It also outlines the peripheral nervous system, somatic vs autonomic systems, and the sympathetic and parasympathetic divisions. Finally, it provides overviews of the main sensory organs - eye, ear, taste/smell, and touch receptors.
This document provides an overview of the nervous system, including its main divisions and components. The nervous system is divided into the central nervous system (CNS), comprising the brain and spinal cord, and the peripheral nervous system (PNS). The CNS is further divided into afferent and efferent divisions for sensory and motor functions. Key cell types include neurons, which communicate via synapses and form reflex arcs, and glial cells like Schwann cells, oligodendrocytes, astrocytes and microglia that support neuronal function.
The nervous system has two main divisions - the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS is made up of the brain and spinal cord and acts as the control center, receiving and sending signals. The PNS includes nerves that connect the CNS to the rest of the body and has two parts - sensory and motor. The nervous system has four primary functions - sensing the world, transmitting information, processing information, and producing responses. It contains neurons and supporting cells called neuroglia that help insulate and protect neurons. The complex brain is divided into the hindbrain, midbrain, and forebrain, each controlling different functions critical for life.
The document summarizes key aspects of the nervous system, including:
- The central nervous system (CNS) composed of the brain and spinal cord. The peripheral nervous system (PNS) connects the CNS to the rest of the body.
- The brain is divided into sections that control different functions like thinking, movement, senses, and basic body processes. Brain size does not necessarily correlate with intelligence.
- The left and right hemispheres of the brain control opposite sides of the body and have different functions related to logic, creativity, and language.
- The spinal cord carries signals between the brain and body to control muscles and receive sensory feedback.
- Reflexes bypass conscious thought
This document provides an overview of spinal cord anatomy and disorders. It describes the spinal cord's location and functions, including conduction of information between the brain and body, control of locomotion, and reflexes. Anatomically, it details the spinal cord's segments, gray and white matter structures, vascular supply, and coverings. Regarding disorders, it notes that compressive myelopathies can be extradural or intradural, and intrinsic lesions can be intramedullary. Clinical features of spinal cord disorders include patterns of motor, sensory and autonomic dysfunction depending on the level and nature of the lesion.
The document summarizes the nervous system and chemical coordination system in three parts:
1. The central nervous system includes the brain and spinal cord. The brain is made up of the forebrain, midbrain, and hindbrain. The spinal cord runs through the vertebral column and contains grey and white matter.
2. The peripheral nervous system includes ganglia and nerves that connect the central nervous system to other parts of the body. There are motor and sensory neurons that carry signals between the central nervous system and other body systems.
3. The chemical coordination system includes the endocrine system made up of endocrine glands that secrete hormones to regulate processes like growth, metabolism, and reproduction.
The document summarizes the main components and functions of the human nervous system. It describes the central nervous system including the brain and spinal cord. It also describes the peripheral nervous system including cranial nerves and spinal nerves. Finally, it discusses the different types of neurons, their functions, and how they transmit signals in the body.
This document summarizes the structure and function of the human nervous system. It describes the basic unit of the nervous system, the neuron, including its cell body, dendrites, and axon. It explains how axons are myelinated and the role of nodes of Ranvier in nerve signal transmission. It then discusses the synapse, reflex arc, and the central and peripheral nervous systems. Within the central nervous system it outlines the main functions of the brain regions including the cerebrum, cerebellum, and medulla oblongata. It concludes by describing the sympathetic and parasympathetic divisions of the autonomic nervous system and some of their roles in stress response and relaxation.
nervous system ppt pptx anatomy system of nervesPhebeLois1
The nervous system has two main divisions - the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS is made up of the brain and spinal cord, which act as integrative and control centers. The PNS includes nerves that connect the CNS to the rest of the body and transmit sensory information to the CNS and motor commands from the CNS. Neurons are the basic functional units and come in sensory, motor, and interneuron types. Supporting glial cells insulate and protect neurons. The nervous system uses electrical and chemical signals to sense the environment, integrate information, and coordinate responses via pathways like ascending and descending tracts in the spinal cord and reflex arcs.
This document provides an overview of the nervous system, including its central and peripheral components. It describes the main cell types - neurons and glial cells. It discusses the key parts of neurons - dendrites, axons, axon hillock. It outlines the main types of neurons and glial cells in both the central and peripheral nervous systems. It provides details on how neurons communicate at synapses and how glial cells support neuronal function.
This document provides an overview of the nervous system, including its main components and functions. It discusses the peripheral nervous system, spinal cord, and central nervous system. It describes the morphological and functional subdivisions of the nervous system. Key topics covered include the embryonic origins and histological composition of nervous system structures. Reflex arcs and the organization of the spinal cord are also summarized.
The central nervous system is protected by three meningeal membranes and contains interconnected ventricles that circulate cerebrospinal fluid. The spinal cord extends from the foramen magnum to the lumbar vertebrae and functions as a center for spinal reflexes and to conduct nerve impulses. The brain controls muscular movements, regulates organs, interprets sensations, stores memories, and determines personality. It contains structures like the cerebrum, cerebellum, and brainstem. The cerebrum is divided into lobes and regions that control motor functions, sensory interpretation, memory, reasoning, and more.
The document provides an overview of the nervous system, including key structures and functions. It discusses the meninges surrounding the central nervous system, ventricles within the brain, cerebrospinal fluid, spinal cord tracts and reflex arcs. It also summarizes the major parts and lobes of the brain, cerebral cortex functions, and the peripheral and autonomic nervous systems.
Lecture notes and diagrams to help high school anatomy and physiology students learn the general functions of the nervous system and types of glial support nerve cells, types of neurons and anatomy of typical neurons.
The nervous system can be divided into the central nervous system (CNS) and peripheral nervous system (PNS). The CNS consists of the brain and spinal cord and is responsible for integrating sensory information and coordinating motor commands. The PNS has two parts - the cerebrospinal part made up of cranial and spinal nerves, and the autonomic nervous system. There are two main cell types in the nervous system - neurons, which transmit signals, and neuroglia, which provide support and insulation. The autonomic nervous system has two divisions - the parasympathetic and sympathetic systems, which work in opposition to activate "rest and digest" and "fight or flight" responses respectively.
The document summarizes key aspects of the central nervous system. It describes the main parts and functions of the brain and spinal cord, including the meninges, ventricles, cerebrospinal fluid, spinal cord structure, brain lobes and areas, diencephalon, limbic system, brain stem, reticular formation, and cerebellum. It also discusses reflexes, motor and sensory areas, memory, sleep, and left and right hemisphere dominance.
The nervous system is divided into the central nervous system (CNS) and peripheral nervous system (PNS). The CNS contains the brain and spinal cord for integrating and controlling signals, while the PNS uses nerves to connect the CNS to the rest of the body. Neurons are the basic functional units that transmit signals via electrical impulses. Supporting glial cells insulate neurons and provide nutrients. Sensory neurons carry signals to the CNS, while motor neurons carry signals from the CNS to muscles and glands. Reflexes are rapid, involuntary responses mediated by neural pathways and occurring without conscious thought.
The document discusses the structure and function of the nervous system. It describes the three basic functions of the nervous system as sensory, integrative, and motor. It then explains the divisions of the nervous system including the central nervous system (CNS) which contains the brain and spinal cord, and the peripheral nervous system (PNS) which contains nerves that connect the CNS to sensory receptors and effectors. Within the PNS it describes the somatic, autonomic, and enteric nervous systems. It also discusses the basic cell types of neural tissue including neurons and neuroglia, and provides diagrams of neuron structure and function.
The document discusses the structure and function of the nervous system. It describes the three basic functions of the nervous system as sensory, integrative, and motor. It then explains the divisions of the nervous system including the central nervous system (CNS) which contains the brain and spinal cord, and the peripheral nervous system (PNS) which contains nerves that connect the CNS to sensory receptors and effectors. Within the PNS it describes the somatic, autonomic, and enteric nervous systems. It also discusses the basic cell types of neural tissue including neurons and neuroglia, and provides diagrams of neuron structure and function.
The document summarizes the key functions and components of the human nervous system. It discusses how the nervous system allows for communication and coordination within the body through the central nervous system (brain and spinal cord) and peripheral nervous system (nerves connecting to muscles and organs). It also describes the basic unit (neuron), divisions (central vs peripheral), and roles of the nervous system in sensation, voluntary control, and involuntary processes.
This document outlines key concepts related to the nervous system. It defines neurons and their parts, and describes how nerve impulses are transmitted. It explains the structure and function of the central nervous system, including the brain regions and spinal cord. It also outlines the peripheral nervous system, somatic vs autonomic systems, and the sympathetic and parasympathetic divisions. Finally, it provides overviews of the main sensory organs - eye, ear, taste/smell, and touch receptors.
This document provides an overview of the nervous system, including its main divisions and components. The nervous system is divided into the central nervous system (CNS), comprising the brain and spinal cord, and the peripheral nervous system (PNS). The CNS is further divided into afferent and efferent divisions for sensory and motor functions. Key cell types include neurons, which communicate via synapses and form reflex arcs, and glial cells like Schwann cells, oligodendrocytes, astrocytes and microglia that support neuronal function.
The nervous system has two main divisions - the central nervous system (CNS) and the peripheral nervous system (PNS). The CNS is made up of the brain and spinal cord and acts as the control center, receiving and sending signals. The PNS includes nerves that connect the CNS to the rest of the body and has two parts - sensory and motor. The nervous system has four primary functions - sensing the world, transmitting information, processing information, and producing responses. It contains neurons and supporting cells called neuroglia that help insulate and protect neurons. The complex brain is divided into the hindbrain, midbrain, and forebrain, each controlling different functions critical for life.
The document summarizes key aspects of the nervous system, including:
- The central nervous system (CNS) composed of the brain and spinal cord. The peripheral nervous system (PNS) connects the CNS to the rest of the body.
- The brain is divided into sections that control different functions like thinking, movement, senses, and basic body processes. Brain size does not necessarily correlate with intelligence.
- The left and right hemispheres of the brain control opposite sides of the body and have different functions related to logic, creativity, and language.
- The spinal cord carries signals between the brain and body to control muscles and receive sensory feedback.
- Reflexes bypass conscious thought
This document provides an overview of spinal cord anatomy and disorders. It describes the spinal cord's location and functions, including conduction of information between the brain and body, control of locomotion, and reflexes. Anatomically, it details the spinal cord's segments, gray and white matter structures, vascular supply, and coverings. Regarding disorders, it notes that compressive myelopathies can be extradural or intradural, and intrinsic lesions can be intramedullary. Clinical features of spinal cord disorders include patterns of motor, sensory and autonomic dysfunction depending on the level and nature of the lesion.
Chronic progressive external ophthalmoplegiaPS Deb
Chronic progressive external ophthalmoplegia (CPEO) is a descriptive term for a heterogeneous group of disorders characterized by chronic, progressive, bilateral, and usually symmetric ocular motility deficit and ptosis, without pain, proptosis and pupil involvement. Commonly a syndrome of Mitochondrial Cytopathy.
This document discusses different theories of motivation in the workplace. It covers intrinsic and extrinsic motivators, Maslow's hierarchy of needs, Herzberg's two-factor theory, and equity theory. The document also examines what motivates people in different countries, what employees value in their jobs, and how the 40-hour work week emerged. A key point is that while pleasure, leisure, and happiness are often seen as motivators, a truly happy and motivated person would feel compelled to act due to their nature but remain detached from outcomes and desires.
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.
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.
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 summarizes research on the organization and function of the motor nervous system and motor cortex. It describes that the primary motor cortex directly controls spinal motor neurons to enable fine movement control. The dorsal premotor cortex contains movement-related neurons that encode sensorimotor transformations for visually and sensory-cued movements. The ventral premotor cortex encodes learned motor acts and fires before movement execution. Long-term practice leads to more extensive representation of movements in the primary motor cortex, demonstrating the adaptability and plasticity of cortical motor areas.
This document discusses the motor nervous system and motor paralysis from multiple levels including:
- The motor cortex and its connections to other brain areas
- The extrapyramidal and pyramidal systems
- Different types of apraxia and their lesion locations
- Lesions of the brainstem, spinal cord, nerves and muscles that can cause hemiplegia, monoplegia, or paraplegia
- The clinical features and localization of upper and lower motor neuron lesions
- Specific motor syndromes and their etiologies
It provides an overview of the organization of the motor system and localization of lesions throughout the nervous system that can result in different clinical motor deficits.
The document discusses the basal ganglia, including its subdivisions and connections. It describes the basal ganglia's role in voluntary movement, including initiation and control of movement. Disorders of the basal ganglia like Parkinson's disease can cause issues with movement including bradykinesia, rigidity, and tremors. Lesion and stimulation studies in animals help explain how abnormalities in basal ganglia circuits lead to motor symptoms.
This document provides information about myoclonus, which are sudden, shock-like contractions of muscles. It describes different types of myoclonus including focal, cortical, brainstem, spinal, peripheral, multifocal, generalized, essential, and childhood myoclonic epilepsies. Diagnostic tests like EMG and EEG are discussed. Various causes and treatment options are also mentioned.
This document discusses athetosis and dystonia. It defines athetosis as irregular, slow writhing movements, often of the extremities and fingers. Dystonia is defined as an abnormal sustained muscle contraction causing twisting movements and abnormal postures. The document describes the clinical presentations and patterns of movement seen in athetosis. It discusses the potential pathophysiology of athetosis involving lesions in the frontal lobes, parietal lobes, and putamen. Causes of athetosis in children and adults are provided. Dystonia is similarly defined and classified. Potential pathology, types, hereditary forms, and secondary causes of dystonia are outlined in detail.
This document discusses tic disorders, including Tourette Syndrome. It describes the characteristics and symptoms of simple and complex motor and vocal tics. Tourette Syndrome is defined by the presence of multiple motor and vocal tics with onset before age 18 that have been present for over a year. The document discusses the pathophysiology involving dopamine dysfunction and potential genetic and environmental factors. Diagnostic criteria from the Tourette Syndrome Study Group and DSM-IV are provided. Prognosis is noted to be generally good, with marked improvement in tics occurring in late teens to early twenties for most patients.
1. Chorea is a state of excessive, spontaneous, irregular movements that are randomly distributed and abnormal in character. It can range from mild restlessness to violent disabling movements.
2. Ballismus involves proximal, flinging, violent involuntary movements. Both chorea and ballismus are associated with basal ganglia dysfunction and abnormal neurotransmitter levels like decreased GABA and increased dopamine.
3. Causes of chorea and ballismus include infections, metabolic and endocrine disorders, drugs, trauma, vascular events, tumors, and hereditary conditions like Huntington's disease. Treatment involves reducing dopamine levels with antipsychotics or GABA agonists, as well as surgical procedures like pallidotomy or thalamotomy
This document provides information on different types of tremors, including their causes, characteristics, and pathophysiology. It discusses rest tremor seen in Parkinson's disease and other conditions. It also covers postural tremor, physiological tremor, essential tremor, kinetic tremor, and cerebellar intention tremor. For each type of tremor, the summary highlights key details like involved areas of the brain, typical frequencies, symptoms, and potential treatments.
This is a short presentation at Down Town Hospital clinical meeting for DNB Medicine students. It dose not cover the all aspects of stroke care especially Thrombolysis, since it is difficult to practice for Medical specialist, and ischemic stroke is not common in North East India
This document discusses the neurologic manifestations of HIV/AIDS in India. Some key points include:
- Opportunistic infections like cryptococcal meningitis and tuberculosis account for the majority (around 70%) of neurologic events seen in HIV patients in India.
- Conditions like progressive multifocal leukoencephalopathy and myelopathy are relatively rare compared to Western countries.
- Common neurologic manifestations include meningitis, mass lesions in the brain, and various neuropathies.
- The pattern of neurologic involvement tends to change as the CD4 count declines, with more severe complications occurring at very low CD4 levels.
10 Benefits an EPCR Software should Bring to EMS Organizations Traumasoft LLC
The benefits of an ePCR solution should extend to the whole EMS organization, not just certain groups of people or certain departments. It should provide more than just a form for entering and a database for storing information. It should also include a workflow of how information is communicated, used and stored across the entire organization.
Travel Clinic Cardiff: Health Advice for International TravelersNX Healthcare
Travel Clinic Cardiff offers comprehensive travel health services, including vaccinations, travel advice, and preventive care for international travelers. Our expert team ensures you are well-prepared and protected for your journey, providing personalized consultations tailored to your destination. Conveniently located in Cardiff, we help you travel with confidence and peace of mind. Visit us: www.nxhealthcare.co.uk
These lecture slides, by Dr Sidra Arshad, offer a simplified look into the mechanisms involved in the regulation of respiration:
Learning objectives:
1. Describe the organisation of respiratory center
2. Describe the nervous control of inspiration and respiratory rhythm
3. Describe the functions of the dorsal and respiratory groups of neurons
4. Describe the influences of the Pneumotaxic and Apneustic centers
5. Explain the role of Hering-Breur inflation reflex in regulation of inspiration
6. Explain the role of central chemoreceptors in regulation of respiration
7. Explain the role of peripheral chemoreceptors in regulation of respiration
8. Explain the regulation of respiration during exercise
9. Integrate the respiratory regulatory mechanisms
10. Describe the Cheyne-Stokes breathing
Study Resources:
1. Chapter 42, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 36, Ganong’s Review of Medical Physiology, 26th edition
3. Chapter 13, Human Physiology by Lauralee Sherwood, 9th edition
Cell Therapy Expansion and Challenges in Autoimmune DiseaseHealth Advances
There is increasing confidence that cell therapies will soon play a role in the treatment of autoimmune disorders, but the extent of this impact remains to be seen. Early readouts on autologous CAR-Ts in lupus are encouraging, but manufacturing and cost limitations are likely to restrict access to highly refractory patients. Allogeneic CAR-Ts have the potential to broaden access to earlier lines of treatment due to their inherent cost benefits, however they will need to demonstrate comparable or improved efficacy to established modalities.
In addition to infrastructure and capacity constraints, CAR-Ts face a very different risk-benefit dynamic in autoimmune compared to oncology, highlighting the need for tolerable therapies with low adverse event risk. CAR-NK and Treg-based therapies are also being developed in certain autoimmune disorders and may demonstrate favorable safety profiles. Several novel non-cell therapies such as bispecific antibodies, nanobodies, and RNAi drugs, may also offer future alternative competitive solutions with variable value propositions.
Widespread adoption of cell therapies will not only require strong efficacy and safety data, but also adapted pricing and access strategies. At oncology-based price points, CAR-Ts are unlikely to achieve broad market access in autoimmune disorders, with eligible patient populations that are potentially orders of magnitude greater than the number of currently addressable cancer patients. Developers have made strides towards reducing cell therapy COGS while improving manufacturing efficiency, but payors will inevitably restrict access until more sustainable pricing is achieved.
Despite these headwinds, industry leaders and investors remain confident that cell therapies are poised to address significant unmet need in patients suffering from autoimmune disorders. However, the extent of this impact on the treatment landscape remains to be seen, as the industry rapidly approaches an inflection point.
Does Over-Masturbation Contribute to Chronic Prostatitis.pptxwalterHu5
In some case, your chronic prostatitis may be related to over-masturbation. Generally, natural medicine Diuretic and Anti-inflammatory Pill can help mee get a cure.
DECLARATION OF HELSINKI - History and principlesanaghabharat01
This SlideShare presentation provides a comprehensive overview of the Declaration of Helsinki, a foundational document outlining ethical guidelines for conducting medical research involving human subjects.
- Video recording of this lecture in English language: https://youtu.be/Pt1nA32sdHQ
- Video recording of this lecture in Arabic language: https://youtu.be/uFdc9F0rlP0
- Link to download the book free: https://nephrotube.blogspot.com/p/nephrotube-nephrology-books.html
- Link to NephroTube website: www.NephroTube.com
- Link to NephroTube social media accounts: https://nephrotube.blogspot.com/p/join-nephrotube-on-social-media.html
8 Surprising Reasons To Meditate 40 Minutes A Day That Can Change Your Life.pptxHolistified Wellness
We’re talking about Vedic Meditation, a form of meditation that has been around for at least 5,000 years. Back then, the people who lived in the Indus Valley, now known as India and Pakistan, practised meditation as a fundamental part of daily life. This knowledge that has given us yoga and Ayurveda, was known as Veda, hence the name Vedic. And though there are some written records, the practice has been passed down verbally from generation to generation.
Clinic ^%[+27633867063*Abortion Pills For Sale In Tembisa Central19various
Clinic ^%[+27633867063*Abortion Pills For Sale In Tembisa Central Clinic ^%[+27633867063*Abortion Pills For Sale In Tembisa CentralClinic ^%[+27633867063*Abortion Pills For Sale In Tembisa CentralClinic ^%[+27633867063*Abortion Pills For Sale In Tembisa CentralClinic ^%[+27633867063*Abortion Pills For Sale In Tembisa Central
Overview Perhaps the major reason that neuroscience remains such an exciting field is the wealth of unanswered questions about the fundamental structure and functions of the human brain. To understand this remarkable organ (and the rest of the nervous system), the myriad cell types that constitute the nervous system must be identified, their interconnections traced, and the physiological role of the resulting circuits defined. Adding to these several challenges is the fact that a specialized anatomical vocabulary has arisen to describe the structure of the nervous system, as well as a specialized set of physiological terms to describe its functions. In light of these conceptual and semantic difficulties, comprehending the brain and the rest of the nervous system is greatly facilitated by a general picture of the organization of the nervous system, and by a review of the basic terms and anatomical conventions used in discussing its structure and function.
A flexure in the long axis of the nervous system arose as humans evolved upright posture, leading to an approximately 120° angle between the long axis of the brainstem and that of the forebrain (A). The consequences of this flexure for anatomical terminology are indicated in (B). The terms anterior, posterior , superior , and inferior refer to the long axis of the body, which is straight. Therefore, these terms indicate the same direction for both the forebrain and the brainstem. In contrast, the terms dorsal , ventral , rostral , and caudal refer to the long axis of the central nervous system. The dorsal direction is toward the back for the brainstem and spinal cord, but toward the top of the head for the forebrain. The opposite direction is ventral. The rostral direction is toward the top of the head for the brainstem and spinal cord, but toward the face for the forebrain. The opposite direction is caudal. (C) The major planes of section used in cutting or imaging the brain. To understand the spatial organization of these systems, some additional vocabulary employed to describe them needs to be defined. The terms used to specify location in the central nervous system are the same as those used for the gross anatomical description of the rest of the body ( Figure 1.9 ). Thus, anterior and posterior indicate front and back; rostral and caudal, toward the head and tail; dorsal and ventral, top and bottom; and medial and lateral, the midline or to the side. Nevertheless, the comparison between these coordinates in the body versus the brain can be confusing. For the entire body these anatomical terms refer to the long axis, which is straight. The long axis of the central nervous system, however, has a bend in it. In human and other bipeds, a compensatory tilting of the rostral/caudal axis for the brain is necessary to properly compare body axes to brain axes. Once this adjustment has been made, the other axes for the brain can be easily assigned. The proper assignment of these anatomical axes then dictates the standard planes for histological sections or tomographic images used to study the internal anatomy of the brain (see Figure 1.9C) . Horizontal sections are taken parallel to the rostral/caudal axis of the brain. Sections taken in the plane dividing the two hemispheres are sagittal , and can be further categorized as median and paramedian according to whether the section is near the midline (median or midsagittal) or more lateral (paramedian). Sections in the plane of the face are called frontal or coronal. Different terms are usually used to refer to sections of the spinal cord. The plane of section orthogonal to the long axis of the cord is called transverse , whereas sections parallel to the long axis of the cord are called longitudinal . In a transverse section through the human spinal cord, the dorsal and ventral axes and the anterior and posterior axes indicate the same directions. Tedious though this terminology may be, it is essential for understanding the basic subdivisions of the nervous system.
White Matter vs. Gray Matter Both the spinal cord and the brain consist of white matter = bundles of axons each coated with a sheath of myelin gray matter = masses of the cell bodies and dendrites — each covered with synapses . In the spinal cord, the white matter is at the surface, the gray matter inside. In the brain of mammals , this pattern is reversed. However, the brains of "lower" vertebrates like fishes and amphibians have their white matter on the outside of their brain as well as their spinal cord
The subdivisions and components of the central nervous system. (A) A lateral view indicating the seven major components of the central nervous system. (Note that the position of the brackets on the left side of the figure refers to the vertebrae, not the spinal segments.) (B) The central nervous system in ventral view, indicating the emergence of the segmental nerves and the cervical and lumbar enlargements. (C) Diagram of several spinal cord segments, showing the relationship of the spinal cord to the bony canal in which it lies. The central nervous system (defined as the brain and spinal cord) is usually considered to have seven basic parts: the spinal cord, the medulla, the pons, the cerebellum, the midbrain, the diencephalon, and the cerebral hemispheres . The medulla, pons, and midbrain are collectively called the brainstem; the diencephalon and cerebral hemispheres are collectively called the forebrain. Within the brainstem are found cranial nerve nuclei that either receive input from cranial sensory ganglia via their respective cranial sensory nerves or give rise to axons that constitute cranial motor nerves . In addition, the brainstem is the conduit for several major tracts in the central nervous system. These tracts either relay sensory information from the spinal cord and brainstem to the midbrain and forebrain, or relay motor commands from the midbrain and forebrain back to motor neurons in the brainstem and spinal cord.
Divisions of the Brain Generally, many body functions involve cells in several areas of the brain. However, certain areas of the brain tend to be more important in some functions while other areas dominate the control of other functions. Some major parts of the brain are listed below. Hindbrain : medulla oblongata, cerebellum, pons Midbrain Forebrain : thalamus, hypothalamus, cerebrum The human forebrain (prosencephalon) is made up of a pair of large cerebral hemispheres , called the telencephalon . Because of crossing over of the spinal tracts, the left hemisphere of the forebrain deals with the right side of the body and vice versa. a group of structures located deep within the cerebrum, that make up the diencephalon . Cerebrum The cerebrum became greatly enlarged as evolution progressed from fish to mammals. In reptiles, birds, and mammals, it receives sensory information and coordinates motor responses. Motor responses to the skeletal muscles originate in the cerebrum but are refined and coordinated by the cerebellum. In humans, the cerebrum is the largest part of the brain. Characteristics such as thinking, intelligence, and emotion are controlled here. Olfactory Bulbs - The anterior parts of the cerebral hemispheres are called the olfactory bulbs. It receives input from the olfactory nerves (smell). The olfactory bulbs of primitive vertebrates comprise a large proportion of the cerebrum. Cerebral Cortex - Over evolutionary time, gray matter developed over the cerebrum. This is the cerebral cortex and it is an information-processing center. It increased in size more rapidly than the skull so that it has become folded (convoluted) in order to fit in the skull. The human cerebral cortex is thin (1.5-4 mm thick) and is highly folded to increase its surface area. Intelligence, emotion, creativity, learning, and memory are localized in the cerebral cortex. Lobes of the cerebral cortex The cerebral cortex is divided into four lobes, each receives information from particular senses and processes the information into higher levels of consciousness. Lobe Function Frontal motor functions; permits conscious control of skeletal muscles; contains the primary motor cortex conscious thought Parietal sensory areas from the skin; contains the primary sensory cortex Occipital The primary visual cortex is located within the occipital lobe. Temporal hearing and smell Primary Sensory and Primary Motor Cortex - The primary sensory cortex is a narrow band of cortex tissue that extends from one side of the cortex near the ear over the top of the brain to the other side. Information from sensory receptors in the skin arrive at this area. The motor cortex is a band of cortex tissue directly anterior (in front) of the primary sensory cortex. Signals that control the skeletal muscles originate in this area. Corpus Callosum The corpus callosum contains neurons that cross from one side of the brain to the other, allowing each half to communicate with each other. The corpus callosum of people with severe epilepsy is sometimes cut to reduce the frequency and intensity of seizures. Researchers presented some of these people with words such as cowboy. When viewing this word, the first three letters (cow) are viewed in the left visual field of each eye and is projected onto the right half of the brain. These people could write the word cow with their left hand because their right brain controls the left side of the body and it is aware of the word cow but not boy. Their other hand could only write the word ''boy". Moreover, they could only say "boy" because language is controlled by the left hemisphere. Although they could see themselves write cow, they could only say boy.
Thalamus the thalamus serves as a relay area to the cerebrum from other parts of the spinal cord and brain. For example, it receives sensory input (except smell) and sends to appropriate areas of the cerebral cortex. The cerebral cortex also sends information to the thalamus which then transmits this information to other areas of the brain and spinal cord. The Thalamus contains part of the reticular formation (see below).
Hypothalamus Functions: Body Temperature, Emotions, Hunger, Thirst, Circadian Rhythms The hypothalamus is composed of several different areas and is located at the base of the brain. It is only the size of a pea (about 1/300 of the total brain weight), but it is responsible for some very important behaviors. One important function of the hypothalamus is the control of body temperature. The hypothalamus acts like a "thermostat" by sensing changes in body temperature and then sending out signals to adjust the temperature. For example, if you are too hot, the hypothalamus detects this and then sends out a signal to expand the capillaries in your skin. This causes blood to be cooled faster. The hypothalamus also controls the pituitary.
Basal Ganglia Functions: Movement The basal ganglia are a group of structures, including the globus pallidus, caudate nucleus, subthalamic nucleus, putamen and substantia nigra, that are important in coordinating movement.
Limbic System The limbic system contains neural pathways that connect portions of the cortex, thalamus, hypothalamus, and basal nuclei (several areas deep within the cerebrum). It causes pleasant or unpleasant feelings about experiences (rage, pain, pleasure, sorrow). This guides the individual into behavior that is likely to increase survival. The hippocampus is also important for memory
Cerebellum The cerebellum coordinates and refines complex muscle movements. Movement information that is initiated in higher brain centers (the cerebral cortex) is compared to the actual position of the limbs. The cerebellum then adjusts and refines the movement. It is large in birds because flight requires considerable coordination. Functions: Movement, Balance, Posture The word "cerebellum" comes from the Latin word for "little brain." The cerebellum is located behind the brain stem. In some ways, the cerebellum is a bit like the cerebral cortex: the cerebellum is divided into hemispheres and has a cortex that surrounds these hemispheres.
Brain stem Functions: Breathing, Heart Rate, Blood Pressure The brain stem is a general term for the area of the brain between the thalamus and spinal cord. Structures within the brain stem include the medulla, pons, tectum, reticular formation and tegmentum. Some of these areas are responsible for the most basic functions of life such as breathing, heart rate and blood pressure. Medulla oblongata The medulla looks like a swollen tip to the spinal cord. Nerve impulses arising here rhythmically stimulate the intercostal muscles and diaphragm — making breathing possible regulate heartbeat regulate the diameter of arterioles thus adjusting blood flow. The neurons controlling breathing have mu (µ) receptors , the receptors to which opiates , like heroin, bind. This accounts for the suppressive effect of opiates on breathing. Destruction of the medulla causes instant death. Pons The pons seems to serve as a relay station carrying signals from various parts of the cerebral cortex to the cerebellum. Nerve impulses coming from the eyes , ears , and touch receptors are sent on the cerebellum. The pons also participates in the reflexes that regulate breathing. The reticular formation is a region running through the middle of the hindbrain (and on into the midbrain). It receives sensory input (e.g., sound) from higher in the brain and passes these back up to the thalamus. The reticular formation is involved in sleep, arousal (and vomiting). The Midbrain The midbrain (mesencephalon) occupies only a small region in humans (it is relatively much larger in "lower" vertebrates). We shall look at only three features: the reticular formation : collects input from higher brain centers and passes it on to motor neurons. the substantia nigra : helps "smooth" out body movements; damage to the substantia nigra causes Parkinson's disease. the ventral tegmental area ( VTA ): packed with dopamine -releasing neurons that are activated by nicotinic acetylcholine receptors and whose projections synapse deep within the forebrain. The VTA seems to be involved in pleasure: nicotine, amphetamines and cocaine bind to and activate its dopamine-releasing neurons and this may account — at least in part — for their addictive qualities.
Cranial Nerves and Spinal Nerves Humans have 12 pairs of cranial nerves and 31 pairs of spinal nerves . Cranial nerves are sensory, motor, or mixed, and all but the vagus are involved with the head and neck region; the vagus nerve manages the internal organs. Spinal nerves are all mixed nerves. Their regular arrangement reflects the segmentation of the human body. Spinal nerves are connected to the spinal cord by two branches called roots. The dorsal root contains sensory neurons . The dorsal root ganglion contains the cell bodies of sensory neurons. Sensory neurons therefore have long dendrites. The ventral root contains motor neurons. Motor neurons have short dendrites and long axons.
The Ventricular System The cerebral ventricles are a series of interconnected, fluid-filled spaces that lie in the core of the forebrain and brainstem . The presence of ventricular spaces in the various subdivisions of the brain reflects the fact that the ventricles are the adult derivatives of the open space or lumen of the embryonic neural tube . Although they have no unique function, the ventricular spaces present in sections through the brain provide another useful guide to location. The largest of these spaces are the lateral ventricles (one within each of the cerebral hemispheres). These particular ventricles are best seen in frontal sections, where their ventral surface is usually defined by the basal ganglia, their dorsal surface by the corpus callosum, and their medial surface by the septum pellucidum , a membranous tissue sheet that forms part of the midline sagittal surface of the cerebral hemispheres. The third ventricle forms a narrow midline space between the right and left thalamus, and communicates with the lateral ventricles through a small opening at the anterior end of the third ventricle (called the interventricular foramen). The third ventricle is continuous caudally with the cerebral aqueduct , which runs though the midbrain. At its caudal end, the aqueduct opens into the fourth ventricle , a larger space in the dorsal pons and medulla. The fourth ventricle narrows caudally to form the central canal of the spinal cord. The ventricles are filled with cerebrospinal fluid , and the lateral, third, and fourth ventricles are the site of the choroid plexus , which produces this fluid. The cerebrospinal fluid percolates through the ventricular system and flows into the subarachnoid space through perforations in the thin covering of the fourth ventricle; it is eventually absorbed by specialized structures called arachnoid villi or granulations , and returned to the venous circulation. Figure 1.17. The ventricular system of the human brain. (A) Location of the ventricles as seen in a transparent left lateral view. (B) Table showing the ventricular spaces associated with each of the major subdivisions of the brain. (See Chapter 22 for an account of brain development that more fully explains the origin of the ventricular spaces.) Figure 1.18. The meninges. Upper left panel is a midsagittal view showing the three layers of the meninges in relation to the skull and brain. Right panels are blowups to show detail. The Meninges The cranial cavity is conventionally divided into three regions called the anterior, middle, and posterior cranial fossae. Surrounding and supporting the brain within this cavity are three protective tissue layers, which also extend down the brainstem and the spinal cord. Together these layers are called the meninges ( Figure 1.18 ). The outermost layer of the meninges is called the dura mater because it is thick and tough. The middle layer is called the arachnoid mater because of spiderlike processes called arachnoid trabiculae that extend from it toward the third layer, the pia mater , a thin, delicate layer of cells that closely invests the surface of the brain. Since the pia closely adheres to the brain as its surface curves and folds, whereas the arachnoid does not, there are placescalled cisterns where the subarachnoid space is especially large. The major arteries supplying the brain course through the subarachnoid space where they give rise to branches that penetrate the substance of the hemispheres. The subarachnoid space is therefore a frequent site of bleeding following trauma. A collection of blood between the meningeal layers is referred to as a subdural or subarachnoid hemorrhage, as distinct from bleeding within the brain itself.
The Spinal Cord The vertebrae surround and protect the spinal cord. Cerebrospinal fluid within the central canal functions to cushion the spinal cord. Many sensory - motor reflex connections are in the spinal cord. Interneurons often lie between sensory and motor neurons . White matter White matter contains tracts that connect the brain and the spinal cord. The white color is due to the myelin sheaths. Gray matter Gray matter looks gray because it is unmyelinated. It contains the short interneurons that connect many sensory and motor neurons. Sensory neurons enter the gray matter and the axons of motor neurons leave it. The cell bodies of these motor neurons are located in the gray matter. 31 pairs of spinal nerves arise along the spinal cord. These are "mixed" nerves because each contain both sensory and motor axons. However, within the spinal column, all the sensory axons pass into the dorsal root ganglion where their cell bodies are located and then on into the spinal cord itself. all the motor axons pass into the ventral roots before uniting with the sensory axons to form the mixed nerves. The spinal cord carries out two main functions: It connects a large part of the peripheral nervous system to the brain. Information (nerve impulses) reaching the spinal cord through sensory neurons are transmitted up into the brain. Signals arising in the motor areas of the brain travel back down the cord and leave in the motor neurons. The spinal cord also acts as a minor coordinating center responsible for some simple reflexes like the withdrawal reflex . The interneurons carrying impulses to and from specific receptors and effectors are grouped together in spinal tracts .
Nerves Nerves are bundles of neurons; either long dendrites and/or long axons. There are no cell bodies in nerves. The cell bodies are in the ganglia (PNS) or nuclei (in gray matter of the CNS). Most nerves contain both kinds of neurons (sensory and motor). The sensory neurons conduct information to the CNS, the motor neurons conduct away from the CNS. All of the neurons in some nerves conduct in the same direction. These nerves contain either sensory or motor neurons.
Animal evolution has generated a wide range of species including single-celled animals and multicellular animals including invertebrates and vertebrates (left column, indicating time since common ancestor with humans). All of these animals show behavioural responses to their environment with vertebrates showing the most complex behaviours. Only the multicellular animals having anatomically specialised nerve cells forming their brains. The synapses that form the junctions between nerve cells are made of many proteins organised together into 'molecular signal processors' (middle column, Synapse protein complexity). In vertebrates and invertebrates, these proteins control psychological functions including learning and memory. Surprisingly, these synapse molecules exist in single-celled animals as a simple set of proteins (where they control response to environment), and this set was built upon to form a larger set used in the brains of invertebrates. This invertebrate set was expanded further in the brains of vertebrate species. The correlation between numbers of nerve cells in the brain of animals and the number of synaptic proteins shows that both contribute to the differences in species (right column).
Cell Body In many ways, the cell body is similar to other types of cells. It has a nucleus with at least one nucleolus and contains many of the typical cytoplasmic organelles. It lacks centrioles, however. Because centrioles function in cell division, the fact that neurons lack these organelles is consistent with the amitotic nature of the cell. Dendrites Dendrites and axons are cytoplasmic extensions, or processes, that project from the cell body. They are sometimes referred to as fibers. Dendrites are usually, but not always, short and branching, which increases their surface area to receive signals from other neurons. The number of dendrites on a neuron varies. They are called afferent processes because they transmit impulses to the neuron cell body. There is only one axon that projects from each cell body. It is usually elongated and because it carries impulses away from the cell body, it is called an efferent process. Axon An axon may have infrequent branches called axon collaterals. Axons and axon collaterals terminate in many short branches or telodendria. The distal ends of the telodendria are slightly enlarged to form synaptic bulbs. Many axons are surrounded by a segmented, white, fatty substance called myelin or the myelin sheath. Myelinated fibers make up the white matter in the CNS, while cell bodies and unmyelinated fibers make the gray matter. The unmyelinated regions between the myelin segments are called the nodes of Ranvier.
Cell Body In many ways, the cell body is similar to other types of cells. It has a nucleus with at least one nucleolus and contains many of the typical cytoplasmic organelles. It lacks centrioles, however. Because centrioles function in cell division, the fact that neurons lack these organelles is consistent with the amitotic nature of the cell. .
Dendrites Dendrites and axons are cytoplasmic extensions, or processes, that project from the cell body. They are sometimes referred to as fibers. Dendrites are usually, but not always, short and branching, which increases their surface area to receive signals from other neurons. The number of dendrites on a neuron varies. They are called afferent processes because they transmit impulses to the neuron cell body. There is only one axon that projects from each cell body. It is usually elongated and because it carries impulses away from the cell body, it is called an efferent process.
Axon An axon may have infrequent branches called axon collaterals. Axons and axon collaterals terminate in many short branches or telodendria. The distal ends of the telodendria are slightly enlarged to form synaptic bulbs. Many axons are surrounded by a segmented, white, fatty substance called myelin or the myelin sheath. Myelinated fibers make up the white matter in the CNS, while cell bodies and unmyelinated fibers make the gray matter. The unmyelinated regions between the myelin segments are called the nodes of Ranvier
Saltatory action potential conduction along a myelinated axon. (A) Diagram of a myelinated axon. (B) Local current in response to action potential initiation at a particular site flows locally, as described in . However, the presence of myelin prevents the local current from leaking across the internodal membrane; it therefore flows farther along the axon than it would in the absence of myelin. Moreover, voltage-gated Na+ channels are present only at the nodes of Ranvier. This arrangement means that the generation of active, voltage-gated currents need only occur at these unmyelinated regions. The result is a greatly enhanced velocity of action potential conduction. Panel to the left of the figure legend shows the changing membrane potential as a function of time at the points indicated.
Components Presynaptic terminal Synaptic cleft Postsynaptic membrane Neurotransmitters released by action potentials in presynaptic terminal Synaptic vesicles Diffusion Postsynaptic membrane Neurotransmitter removal When an impulse arrives at the end bulb , the end bulb membrane becomes more permeable to calcium . Calcium diffuses into the end bulb & activates enzymes that cause the synaptic vesicles to move toward the synaptic cleft. Some vesicles fuse with the membrane and release their neurotransmitter (a good example of exocytosis). The neurotransmitter molecules diffuse across the cleft and fit into receptor sites in the postsynaptic membrane. When these sites are filled, sodium channels open & permit an inward diffusion of sodium ions. This, of course, causes the membrane potential to become less negative (or, in other words, to approach the threshold potential). If enough neurotransmitter is released, and enough sodium channels are opened, then the membrane potential will reach threshold. If so, an action potential occurs and spreads along the membrane of the post-synaptic neuron (in other words, the impulse will be transmitted). Of course, if insufficient neurotransmitter is released, the impulse will not be transmitted. Impulse transmission - The nerve impulse (action potential) travels down the presynaptic axon towards the synapse, where it activates voltage-gated calcium channels leading to calcium influx, which triggers the simultaneous release of neurotransmitter molecules from many synaptic vesicles by fusing the membranes of the vesicles to that of the nerve terminal. The neurotransmitter molecules diffuse across the synaptic cleft, bind briefly to receptors on the postsynaptic neuron to activate them, causing physiological responses that may be excitatory or inhibitory depending on the receptor. The neurotransmitter molecules are then either quickly pumped back into the presynaptic nerve terminal via transporters, are destroyed by enzymes near the receptors (e.g. breakdown of acetylcholine by cholinesterase), or diffuse into the surrounding area.
Types of neurotransmitters: 1- Excitatory - neurotransmitters that make membrane potential less negative (via increased permeability of the membrane to sodium) &, therefore, tend to 'excite' or stimulate the postsynaptic membrane 2 - Inhibitory - neurotransmitters that make membrane potential more negative (via increased permeability of the membrane to potassium) &, therefore, tend to 'inhibit' (or make less likely) the transmission of an impulse. One example of an inhibitory neurotransmitter is gamma aminobutyric acid (GABA; shown below). Medically, GABA has been used to treat both epilepsy and hypertension. Another example of an inhibitory neurotransmitter is beta-endorphin, which results in decreased pain perception by the CNS.
Autonomic Nervous System This part of the nervous system sends signals to the heart, smooth muscle, glands, and all internal organs. It is generally without conscious control. The autonomic nervous system uses two or more motor neurons : The cell body of one of the motor neurons is in the CNS. The cell body of the other one is in a ganglion. Sympathetic The sympathetic nervous system prepares the body to deal with emergency situations. This is often called the "fight or flight" response. Stimulation from sympathetic nerves dilates the pupils, accelerates the heartbeat, increases the breathing rate, and inhibits the digestive tract. The neurotransmitter is norepinephrine (similar to epinephrine [adrenaline], the heart stimulant). Sympathetic nerves arise from the middle (thoracic-lumbar) portion of the spinal cord. Parasympathetic When there is little stress, the parasympathetic system tends to slow down the overall activity of the body. It causes the pupils to contract, it promotes digestion, and it slows the rate of heartbeat. The neurotransmitter is acetylcholine. The actual rate of stimulus to each organ is determined by the sum of opposing signals from the sympathetic and parasympathetic systems. Parasympathetic nerves arise from the brain and sacral (near the legs) portion of the cord.
Somatic Nervous System The somatic nervous system provides conscious, voluntary control. It includes all of the nerves that serve the skeletal muscles and the exterior sense organs. Reflex arcs Reflexes are simple, stereotyped and repeatable motor actions (example: movements) brought about by a specific sensory stimulus. The reflex is involuntary but may involve the use of voluntary (skeletal) muscle and nerves. Reflexes are quick and produce behaviors that are typically beneficial. For example, when you fall, reflex arcs immediately act to extend your arm so that your arm prevents your head and body from hitting the ground. Some reflexes involve the brain, others do not. A whole series of responses may occur since some sensory neurons stimulate several interneurons which, in turn send impulses to other parts of the CNS. If you were to fall forward, interneurons would use information from the ears to determine the direction of the fall and extend the arms in a forward direction. If you were to fall toward the left side, interneurons would select neurons that activate muscles to extend your arm to the left side. Example: The stretch reflex The stretch reflex is involved in helping the body maintain its position without having to consciously think about it. When a muscle is stretched, stretch-sensitive receptors are stimulated. An action potential is conducted to the spinal cord. The axon terminals synapse with motor neurons leading right back to the muscles. This causes the muscle to contract to its original position.
Reticular Formation The reticular formation is a net of nerve cells extending from the thalamus through the brain stem (midbrain, pons and medulla oblongata) to the spinal cord. It acts as a filter to incoming stimuli and discriminates important from unimportant. Hundreds of millions of sensory receptors flood the brain; the brain does not have the capacity to deal with even a small fraction of this information, so much of it must be ignored. Examples: You may be unaware of conversation in a crowded situation but the system alerts you when you hear your name. You can sleep in the presence of some kinds of sounds but others will wake you. The reticular activating system (RAS) is the part of the reticular formation that maintains wakefulness. Sleep centers are located in the reticular formation. Neurons in one sleep center secrete serotonin , a chemical that inhibits the RAS and thus causes drowsiness and sleep. Another sleep center secretes factors that counteract serotonin and bring about wakefulness. Damage to these centers can lead to unconsciousness or coma
Memory The limbic system is involved in memory formation. The hippocampus , a structure that is deep in the cerebrum and a part of limbic system, is necessary to form new memories. People with a damaged hippocampus cannot remember things since the time the damage occurred but can remember from before. Short-term memory is probably stored as electrical differences because they can be removed by the application of an electrical shock. Long-term memory is probably stored as new or different synapses. Research on snails shows that learning is associated with an increased number of synapses. Forgetting is associated with a decreased number. Disuse can cause a synapse to wither and sever the connection between two neurons. Intensively stimulated synapses form stronger connections, grow, or sprout buds to form more connections. Memory appears to be stored in sensory areas of the cerebrum.