Anatomy Nervous System PDF

The Nervous System By Ass. Prof. Joseph Amin  Introduction The nervous system controls and integrates the activities of the other system. It helps the individual to survive by keeping the internal environment (homeostasis) and adapting to th...

The Nervous System By Ass. Prof. Joseph Amin  Introduction The nervous system controls and integrates the activities of the other system. It helps the individual to survive by keeping the internal environment (homeostasis) and adapting to the external environment The structural and functional unit of the nervous system is the Neuron (nerve cell)  Types of neurons: Structural classification: According to number of processes (nerve fibers) Multipolar: Many dendrites : they bring impulses to the cell body (input) One axon: it sends impulses from the cell body (output) Bipolar: one dendrite & one axon One process that divides into peripheral branch acts as dendrite and Pseudouniopolar: a central branch acts as axon Dendrites Axon Multipolar Bipolar Pseudouniopolar Functional classification: According to the direction of nerve impulse Motor (efferent): Carries impulses away from the Central nervous system (multipolar) Sensory (Afferent): Carries impulses toward the CNS (pseudounipolar) Interneurons: Coordinates the neurons inside CNS Nucleus: Collection of cell bodies inside the CNS Ganglion: Collection of cell bodies outside the CNS Nerve: Tract Bundle of nerve fibers outside the CNS Ganglion Tract: Bundle of nerve fibers inside the CNS Nucleus  Nervous system Anatomical divisions Central nervous system Peripheral nervous system C.N.S P.N.S Brain Spinal cord Cranial nerves Spinal nerves Functional divisions Autonomic nervous system Somatic nervous system  Central nervous system C.N.S Protected by bones (cranium & vertebrae) Covered by 3 meninges - Pia mater (inner coat) - Arachnoid mater (middle coat) - Dura mater (outer coat) The space between pia & arachnoid called subarachnoid space that contains Cerebrospinal fluid (C.S.F Structure of CNS : grey matter (nerve cell bodies) white matter (myelinated nerve fibers)  Brain Cerebrum Brain stem Cerebellum Posterior view Superior view Medial view of Lateral view midsagittal section ❑ The brain consists of Cerebrum >>>> 2 Cerebral hemispheres Cerebellum >>> 2 Cerebellar hemispheres Brain stem  Brain stem It has 3 parts Midbrain, Pons & medulla oblongata Midbrain Pons Medulla oblongata -Functions: - Connects the spinal cord with higher centers in cerebrum & cerebellum - Gives attachment to 10 cranial nerves - Site of some vital centers e.g. respiratory center  Spinal cord - It generally cylindrical in shape about 45 cm in length - Begins at lower end of medulla oblongata just below foramen magnum - Ends opposite lower border of first lumbar vertebra (L1) (adults) cross section, the white matter is peripheral, and the grey matter surrounds the central canal in the form of H shape with 2 anterior horns. containing the motor neurons and 2 posterior horns containing the sensory neurons - It is divided functionally into 31 segments, (8 cervical, 12 thoracic, 5 lumbar, 5 sacral & 1 coccygeal) - Each segment gives attachment to one pair of spinal nerves  Peripheral nervous system Cranial nerves Spinal nerves (12 pairs) (31 pairs)  Peripheral nervous system Peripheral nerve Bundles of nerve fibers surrounded by connective tissue sheath (epineurium) Types: 1- Motor nerves: contains only motor fibers (bundles of multipolar neurons axons) 2- Sensory nerves: contains only sensory fibers (bundles of the peripheral processes of pseudonuipolar neurons) 3- Mixed nerves (both); most of the nerves are mixed  Spinal Nerves -31 nerve attached to the spinal cord on each side. Each nerve arises from the spinal cord segment by 2 roots - Anterior (ventral) root: motor fibers (axons of AHC) + (axons of LHC, efferent autonomic) - Posterior (dorsal root: sensory fibers (peripheral processes of pseudo unipolar neuron) -The 2 roots unit forming Nerve trunk -Nerve trunk exits from the intervertebral foramen divides into - ventral ramus Motor + sensory fibers - dorsal ramus Dorsal ramus Supplies : - Muscles of the Back - Skin of the Back  Ventral ramus : - T1- T12 &L1,2 ventral rami send white ramus communicans (preganglionic sympathetic fibers) to sympathetic ganglia - Each ventral ramus receives grey ramus communicans (post ganglionic sympathetic fibers) from sympathetic ganglia  The course of ventral rami of spinal nerves: ▪ C1-C4 communicate to form the cervical plexus. ▪ C5- T1 communicate form the brachial plexus. ▪ T1-T12 run individually to form the intercostal (T1-T11) and subcostal (T12) nerves. ▪ L1-L4 communicate to form the lumbar plexus. ▪ L4- S4 communicate to form the sacral plexus. ▪ S4-Co1 communicate to form the coccygeal plexus.  Cranial nerves 12 nerves on each side, numbered with the Roman numerals (I, II, III…..XII). - 1st & 2nd are attached to cerebrum - 3rd to 12th are attached to the brain stem)  Cranial nerves I Olfactory: - Carries smell from the nasal cavity II Optic: - - Carries visual impulses from the retina of the eyeball III Oculomotor: - Motor supply to 4 extra ocular muscles (muscles which move the eyeball) SR, IR, MR,IO IV Trochlear: - Motor supply to superior oblique (an extra ocular muscle) VI Abducent: Motor supply to lateral rectus (extra ocular muscle)  V Trigeminal: has 3 divisions - Ophthalmic: Carries general sensations from the upper zone of the face - Maxillary: Carries general sensations from the middle zone of the face - Mandibular : Carries general sensations from the lower zone of the face Motor supply to muscles of mastication VII Facial : - Motor supply to the muscles of facial expressions - Carries taste sensation from ant 2/3 of the tongue (special sensory) - Supplies parasympathetic to submandibular & sublingual salivary glands VIII Vestibulo-cochlear: - Carries auditory impulses from the cochlea of inner ear - Carries equilibrium from the vestibule of inner ear  IX Glossopharyngeal: - Carries taste sensation form the post 1/3 of the tongue, - Carries general sensations from Pharynx, posterior 1/3 of the tongue & middle ear - Supplies parasympathetic to parotid gland - Motor supply to stylopharyngeus muscle (pharyngeal muscle) X Vagus : - Supplies parasympathetic to most of GIT, respiratory tract and heart - Motor supply to the muscles of larynx, pharynx - Carries taste sensations from the root of the tongue - Carries general sensations from the auricle XI Accessory: - spinal part Supplies sternomastoid & trapezius muscles - cranial part Distributed through the vagus XII Hypoglossal: Supplies all muscles of the tongue except palatoglossus