General Anatomy Of The Nervous System PDF

Prof. Hoda aAbdel-Aziz ]txep TpyT[Nervous system General Anatomy Of The Nervous System Learning objectives: After this lecture, student should be able to: Know the structure & division of the nervous tissues. Describe the compo...

Prof. Hoda aAbdel-Aziz ]txep TpyT[Nervous system General Anatomy Of The Nervous System Learning objectives: After this lecture, student should be able to: Know the structure & division of the nervous tissues. Describe the components of the central nervous system (brain & spinal cord) and the peripheral nervous system. Describe the formation of spinal nerve. Differentiate between motor and cutaneous nerves. Describe the autonomic nervous system (function & components). Know the effects of nerve lesion (motor & sensory). Introduction: The nervous system is the master controlling and communicating system of the body. -It Communicates through electrical impulses every thoughts, actions, and emotions. Functions: 1. Monitor changes (sensory input) 2. Process and interpret sensory input (integration) 3. Effects a response (motor output) 1 Prof. Hoda aAbdel-Aziz ]txep TpyT[Nervous system Some important definitions: 1-Neuron: It is the anatomical ,functional ,and embryological unite of the nervous system. It is formed of : a)Cell body: it contains the nucleus. b) Processes: they are 2 types 1-The axon (nerve fiber): single,long process which carries nerve impulses away from the cell body. 2- Dendrites: short , multiple processes which carry impulses towards the cell body. 2-Synapse: Site where impulses pass from one neuron to another by contact of the axon of one neuron with the dendrites of the other. The Neuron ►Components of the nervous system: A-The central nervous system (CNS) Brain &spinal cord -Brain & spinal cord are protected by bones ,fluid (cerebro-spinal fluid.CSF).and meninges. -The brain is protected by the skull and spinal cord is protected by the vertebral column. Meninges 2 Prof. Hoda aAbdel-Aziz ]txep TpyT[Nervous system Three membranes that surround and protect the brain and spinal cord:.Dura mater—thick outer layer closest to skull.. Arachnoid mater—middle layer, contains web-like connections.. Pia mater—thin, fibrous inner layer that firmly adheres to brain and spinal cord. N.B : The pia is separated from the arachnoid matter by the subarachnoid space Function of meninges: -These coverings have two major functions: 1-Provide a supportive framework for the cerebral and cranial vasculature. 2-Acting with cerebrospinal fluid to protect the CNS from mechanical damage. 3 Prof. Hoda aAbdel-Aziz ]txep TpyT[Nervous system Subdivisions of the brain: Cerebrum: two cerebral hemisphers. -Brainstem: midbrain, pons, medulla oblongata -Cerebellum : two cerebellar hemisphers. N.B: -The brain shows outer gray matter (cerebral cortex) contains bodies of nerve cells and inner white matter: it contains axons of nerve cells. Spinal cord ►It begins as the downward continuation of the medulla oblongata at the foramen magnum of the skull and ends at the level of lower border of 1st or upper border of 2nd lumber vertebra.It has a central narrow cavity called central canal ►It is divided into 31 segments : -8 Cervical segments -12 Thoracic segments -5 Lumber segments -5 Sacral segments -1 Coccygeal segment 4 Prof. Hoda aAbdel-Aziz ]txep TpyT[Nervous system In tansverse section the spinal cord it shows: -Outer white matter: sensory &motor tracts Sensory tracts carry sensations to the brain while motor tracts carry the higher motor orders to the brain. - Inner gray matter: H shaped area.two anterior horns(motor) and two posterior horns(sensory). The lateral horn is present in the thoracic and upper two lumber segments. It is only source of sympathetic fibers. 5 Prof. Hoda aAbdel-Aziz ]txep TpyT[Nervous system B-The peripheral nervous system 1-Cranial nerves: They are 12 pairs which are named as follows: Number Name Number Name I Olfactory VII Facial II Optic VIII Vestibulo- cochlear III Occulomotor IX Glosso- pharyngeal IV Trochler X Vagus V Trigeminal XI Accessory VI Abducent XII Hypoglossal -Spinal nerves:They are 31 pairs;8 cervical,12 thoracic ,5 lumber,5 sacral and 1 coccygeal spinal nerves. Structure of spinal nerve: -Each spinal nerve is connected to the spinal cord by two roots, anterior (motor) and posterior roots (sensory). -Both anterior & posterior roots unite to form nerve trunk.The spinal nerve is mixed (motor &sensory) 6 Prof. Hoda aAbdel-Aziz ]txep TpyT[Nervous system - -After emerging from the intervertebral foramen, it divides into large anterior ramus and small posterior ramus. - The anterior rami pass anteriorly to supply muscles & skin of the anterolateral body wall and all muscles & skin of the limbs. 7 Prof. Hoda aAbdel-Aziz ]txep TpyT[Nervous system Autonomic Nervous system a) The sympathetic system: -It is connected centrally to the spinal cord segments from the first thoracic to the third lumbar (thoraco-lumbar). -It prepares the body for emergency. b) The parasympathetic system: It is divided into (cranio-sacral): 1- The Cranial part :in the cranial nerves 3, 7, 9, 10. 2-The sacral part :which is connected centrally with the sacral segments 2, 3 and 4 of the spinal cord. -Activities of the parasympathetic system aim at conserving and restoring energy of the body 8