HUMAN NERVOUS SYSTEM 1. CENTRAL NERVOUS SYSTEM2. PERIPHERAL NERVOUS SYSTEM
CENTRAL NERVOUS SYSTEM OF HUMAN BEING► The human central nervous system is made up of;► 1. Brain► 2. Spinal cord► The complete central nervous system consist of up to 100 billions inter-neurons► Brain and spinal cord are protected in protected bony armour, the skull and the vertebral column.► Both the spinal cord and brain are covered in three continuous sheets of connective tissue called meninges.► A plasma like fluid, the cerebrospinal fluid (CSF) bathing the neurons of CNS is yet another protection to CNS.
Fore-Brain:► The human forebrain is made up of;► Telencephalon► Diencephalon► The telencephalon is the largest part of fore-brain it is differentiated into two cereberal hemisphere or cereberum.
FORE-BRAIN► Cereberal cortex is the largest and most complex part of human brain.► By means of a prominent groove, called the longitudinal fissure, the brain is divided into two halves called cerebral hemispheres.► At the base of this fissure lies a thick bundle of nerve fibers, called the corpus callosum, which provides a communication link between the hemispheres Although the right and left hemispheres seem to be a mirror image of one another, there are important functional distinctions.► Each hemisphere of the cerebrum is subdivided into four lobes.
FORE-BRAIN ► Frontal Lobe- associated with reasoning, planning, parts of speech, movement, emotions, and problem solving. ► Parietal Lobe- associated with movement, orientation, recognition, perception of stimuli. ► Occipital Lobe- associated with visual processing. ► Temporal Lobe- associated with perception and recognition of auditory stimuli, memory, and speech.
FORE-BRAIN(DIENCEPHALON): The diencephalon consists of ;1. Thalamus2. Limbic system.1. Thalamus:► The thalamus is a large, dual lobed mass of grey matter cells located at the top of the brainstem, superior to the hypothalamus. The thalamus is a clearing house for sensory impulses as it receives them from different parts of brain and relays them to the appropriate part of the motor cortex.► It controls the pleasure and pain.
FORE-BRAIN(DIENCEPHALON):► Limbic System:► The limbic system, often referred to as the "emotional brain", is found buried within the cerebrum.► Parts of Limbic System:► Hypothalamus► Amygdala► Hippocampus► Some other parts of thalamus
FORE-BRAIN(DIENCEPHALON):► Hypothalamus: Hypothalamus regulates the autonomic nervous system via hormone production and release. Affects and regulates blood pressure, heart rate, Mood and motivation, hormonal body processes, hunger, thirst, sexual arousal, sexual maturation and the sleep/wake cycle.► Amygdala: It involved in signaling the cortex of motivationally significant stimuli such as those related to reward, punishment and fear in addition to social functions such as mating.
FORE-BRAIN(DIENCEPHALON): HIPPOCAMPUS: It belongs to thelimbic system and playsimportant roles inlong-term memory andspatial navigation. InAlzheimers disease thehippocampus is one of thefirst regions of the brain tosuffer damage; memoryproblems and disorientationappear among the firstsymptoms.
MID-BRAIN► The midbrain is located between the two developmental regions of the brain known as the forebrain and hind brain. In mammals, particularly in man, mid brain is relatively very small. Within the midbrain is the reticular formation, which is part of a certain region of the brainstem that influences motor functions. It receives the sensory information from spinal cord and sends them to the fore-brain.
HIND-BRAIN Cerebellum: The cerebellum, or "littlebrain", is similar to thecerebrum in that it has twohemispheres and has a highlyfolded surface or cortex. Thisstructure is associated withregulation and coordinationof movement, posture, andbalance.
HIND-BRAIN► Pons : is a structure located on the brain stem. It is superior to (up from) medulla oblongata, inferior to (down from) the midbrain and ventral to (in front of) the cerebellum. The pons measures about 2.5 cm in length. It mainly controls with sleep, respiration, swallowing, bladder control, hearing, equilibrium, taste, eye movement, facial expressions, facial sensation, and posture.► Reticular formation: is a group of nerve fibers located inside the brainstem. Reticular formation important in regulating Arousal, Attention, Cardiac Reflexes, Motor Functions, consciousness or wakefulness.
HIND-BRAIN Medulla oblongata:► Medulla oblongata also called the myelencephalon, the lowest part of the brainstem. The medulla oblongata looks like a swelling at the tip of the spinal cord.► The medulla oblongata regulates the reflex responses that control breathing, heart beat, blood pressure, coughing, swallowing, hiccupping, sneezing, vomiting, digestion and other essential involuntary functions.
BRAIN-STEM The lower extension of the brain where it connects tothe spinal cord. It is formed by the combination ofmedulla oblongata, pons and mid–brain. Neurologicalfunctions located in the brainstem include thosenecessary for survival (breathing, digestion, heart rate,blood pressure) and for arousal (being awake and alert).The brainstem is the pathway for all fiber tracts passingup and down from peripheral nerves and spinal cord tothe highest parts of the brain.
SPINAL CORD► It is thick, whitish nerve cord that lies below the medulla and extends down through the neural canal of vertebrae up to the hips.► The spinal cord extends down from the brain stem at the base of the skull, enclosed in the vertebral column. Brain and spinal cord in continuity comprise the central nervous system.► The outer layer of the spinal cord consists of white matter, i.e., myelin-sheathed nerve fibers. These are bundled into specialized tracts that conduct impulses triggered by pressure, pain, heat, and other sensory stimuli or conduct motor impulses activating muscles and glands.
SPINAL CORD ANATOMY► The inner layer, or gray matter, has a butterfly-shaped cross-section and is mainly composed of nerve cell bodies. Within the gray matter, running the length of the cord and extending into the brain, lies the central canal through which the cerebrospinal fluid circulates.► The spinal cord mediates the reflex responses to some sensory impulses directly, i.e., without recourse to the brain, as when a persons leg is tapped producing the knee jerk reflex.
PERIPHERAL NERVOUS SYSTEM (PNS)► In man, the peripheral nervous system consists of ►12 pairs of cranial nerves ►31 pairs of spinal nerves► The PNS transmits signals between CNS and rest of the body.► PNS is further divided into• Somatic Nervous System(Voluntary)• Autonomic Nervous System(Involuntary)
Autonomic Nervous System► Autonomic Nervous System is the division of the peripheral nervous system that controls the glands and the muscles of the internal organs.► The Autonomic Nervous System operates on its own and is involuntary.► The two divisions of Autonomic Nervous System are► Sympathetic Nervous System► Parasympathetic Nervous System
Comparison SYMPATHETIC PARASYMPATHETIC NERVOUS SYSTEM NERVOUS SYSTEM► It is formed by the spinal ► It is formed by vagus nerve, nerves arising from thoracic some of the cranial nerves and and lumbar region. spinal nerves arising from► It prepares the body for highly sacral region. energetic activity such as ► It promotes all the internal fight or flight. responses associated with aIt is responsible for relaxed state.► Dilated Pupil It is responsible for► Accelerated Heartbeat ► Contracted Pupil► Slower Digestion ► Slower Heartbeat► Stimulated glucose release ► Stimulated Digestion► Accelerated breathing rate