L12. The Central Nervous System (CNS) PDF

THE CENTRAL NERVOUS SYSTEM(CNS)-1  OBJECTIVES 1) ORGANIZATION OF NERVOUS SYSTEM 2) CENTRAL NERVOUS SYSTEM 3) Peripheral Nervous System 4) Somatic Nervous System 5) Autonomic Nervous System 6) FUNCTIONAL CLASSES OF NEURONS 7) GLIAL CELLS OR NEUROGLIA  ORGANIZATION OF NERVOU...

THE CENTRAL NERVOUS SYSTEM(CNS)-1  OBJECTIVES 1) ORGANIZATION OF NERVOUS SYSTEM 2) CENTRAL NERVOUS SYSTEM 3) Peripheral Nervous System 4) Somatic Nervous System 5) Autonomic Nervous System 6) FUNCTIONAL CLASSES OF NEURONS 7) GLIAL CELLS OR NEUROGLIA  ORGANIZATION OF NERVOUS SYSTEM The Nervous system is organized into 1. Central Nervous System (CNS)  BRAIN  SPINAL CORD 2. Peripheral Nervous System  Nerve fibers that carry information between CNS and other parts of body at periphery.  12 pairs of cranial nerves and 31 pairs of spinal nerves.  Central nervous system (CNS) The central nervous system consists of the brain and spinal cord. It is referred to as "central" because it combines information from the entire body and coordinates activity across the whole organism. CENTRAL NERVOUS SYSTEM – BRAIN – SPINAL CORD  Central nervous system (CNS) In total, around 100 billion neurons and 1000 billion glial cells make up the human brain. Our brain uses around 20 % of our body's total energy. Brain function depends on oxygen and glucose. Brain needs continuous supply of O2 and Glucose. Brain damage results if : - Brain gets no O2 supply for 4 to 5 mins - No glucose supply for 10 mins.  THE BRAIN The brain can be divided into four main lobes: temporal, parietal, occipital and frontal. Temporal lobe: auditory processing region of the brain, housing the auditory cortex. Occipital lobe: visual processing region of the brain, housing the visual cortex. Parietal lobe: integrates sensory information including touch, spatial awareness, and navigation. Frontal lobe: involved in attention, reward, short-term memory, motivation, and planning. planning It includes primary motor  The brain The brain can be divided into four main lobes: temporal, parietal, occipital and frontal. Temporal lobe: for processing sensory input and assigning it emotional meaning. Occipital lobe: visual processing region of the brain, housing the visual cortex. Parietal lobe: integrates sensory information including touch, spatial  Spinal cord Running almost the full length of the back, carries information between the brain and body. From the brainstem, where the spinal cord meets the brain, 31 spinal nerves enter the cord. Along its length, it connects with the nerves of the peripheral nervous system (PNS) that run in from the skin, muscles, and joints. Motor commands from the brain travel  PERIPHERAL NERVOUS SYSTEM (PNS) 12 pairs of cranial nerves and 31 pairs of spinal nerves. Peripheral Nervous System is sub divided into: – Afferent Division (Sensory) – which carry information to CNS – Efferent Division (Motor) – which carry information from CNS to muscle  PERIPHERAL NERVOUS SYSTEM Efferent (Motor) division of PNS is further divide into  Somatic Nervous System – it is under our voluntary control E.g. fibers of motor neuron that supply skeletal muscle.  Autonomic Nervous System – it is not under our control ( involuntary).  PERIPHERAL NERVOUS SYSTEM  Autonomic Nervous System (ANS) ANS– supplies cardiac muscle, smooth - muscle, glands. ANS is divided into:  Sympathetic ANS  Parasympathetic ANS  Enteric NS– in the wall of digestive tract FUNCTIONAL CLASSES OF NEURONS There are THREE functional types of Neurons I. Afferent Neurons– which carry information to CNS. II.Efferent Neurons– which carry information away from CNS (to the periphery). III.Interneurons– They  AFFERENT NEURON Afferent Neuron has sensory RECEPTOR , that generates action potential in response to a particular stimulus. Sensory impulse are taken by axon toward the spinal cord.  EFFERENT NEURON Efferent Neuron lies in the peripheral nervous system. It has cell body in the CNS. Efferent axon leaves the cell body and goes to  Interneurons Interneurons lie in the CNS. About 99% of all neurons are Interneurons. Human CNS has more than 100 billions Interneurons. White and gray matter The CNS can be roughly divided into white and gray matter. As a rule, the brain consists of: 1. outer cortex of gray matter 2. inner area housing tracts of white matter. Both types of tissue contain glial cells, which protect and support neurons. White matter mostly consists of axons and oligodendrocytes (a type of glial cell).  GLIAL CELLS OR NEUROGLIA Glial cells are connective tissue of CNS. Glial cells support the interneurons physically, metabolically, and functionally. They do not conduct nerve impulses. Glial cells are of FOUR types.  GLIAL CELLS OR NEUROGLIA There are 4 type of Glial Cells 1. Astrocytes 2. Oligodendrocytes 3. Microglia 4. Ependymal Cells  1. Astrocytes  Functions  Formation of blood – brain – barrier  Formation of neural scar tissue  2. Oligodendrocytes  Function  Forms myelin sheath around axons in the CNS.  3. Microglia  Functions  Phagocytosis [ defense cells of CNS]  Release nerve growth factor. factor  4. Ependymal Cells  Functions 1. Formation of Cerebrospinal fluid [CSF]. 2. Work as Neural Stem Cell – to form new neurons and glial cells.  Protection Of Brain  Skull bone [covers the brain] and Vertebral column [surrounds the spinal cord].  Meninges – cover brain and spinal cord. Meninges lie between bony covering [outside] and nervous tissue [inside]. Meninges are Dura mater, Arachnoid and Pia mater.  CSF - Cerebrospinal Fluid is present in subarachnoid space. CSF works as  Cerebrospinal Fluid [CSF] It surrounds brain and spinal cord. It is present in subarachnoid space. It is formed by choroid plexuses [capillaries in the piameter] of ventricles in the brain. Volume of CSF is about 125 – 150 ml.  Clinical Note Hydrocephalus [water in the brain]. Occurs if CSF accumulates more, due to the block in its circulation or reabsorption. If hydrocephalus is untreated, increased CSF pressure can lead to brain damage and mental retardation. Treatment – surgically shunting the excess CSF to veins elsewhere in the body.  References Human physiology by Lauralee Sherwood, seventh edition Text book physiology by Guyton &Hall,11th edition Text book of physiology by Linda.s contanzo,third edition 29 Thanks