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spinal cord and spinal nerves.docx

4 Pages

Biological Sciences
Course Code
Kenneth Welch

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The Spinal Cord and Spinal Nerves General Organization of the Nervous System Divisions of the Nervous System • CNS • Brain and spinal cord • In the white matter, axons arranged in tracts and columns • PNS • Remainder of nervous tissue Gross Anatomy of the Spinal Cord Adult spinal cord • Localized enlargements provide innervation to limbs • 31 segments • each segment has a pair of dorsal roots and a pair of ventral roots • Filum terminale • Conus medularis • Spinal nerves extend off cord • Mixed nerves Spinal meninges • Provide physical stability and shock absorption • Three layers • Dura mater • Arachnoid • Pia mater Dura mater • Covers spinal cord • Tapers to coccygeal ligament • Epidural space separates dura mater from walls of vertebral canal Arachnoid • Interior to dura mater are the subdural space, the arachnoid and the subarachnoid space • Subarachnoid space contains CSF Pia mater • Meshwork of elastin and collagen fibers • Innermost meningeal layer • Denticulate ligaments extend from pia mater to dura mater Sectional anatomy of the spinal cord • White matter is myelinated and unmyelinated axons • Gray matter is cell bodies, unmyelinated axons and neuroglia • Projections of gray matter toward outer surface of cord are horns Horns of spinal cord • Posterior gray horn contains somatic and visceral sensory nuclei • Anterior gray horns deal with somatic motor control • Lateral gray horns contain visceral motor neurons • Gray commissures contain axons that cross from one side to the other White matter • Divided into six columns (funiculi) containing tracts • Ascending tracts relay information from the spinal cord to the brain • Descending tracts carry information from the brain to the spinal cord Spinal Nerves 31 pairs of spinal nerves • Nerves consist of: • Epineurium • Perineurium • Endoneurium Spinal nerves • White ramus (myelinated axons) • Gray ramus (unmyelinated axons that innervate glands and smooth muscle) • Dorsal ramus (sensory and motor innervation to the skin and muscles of the back) • Ventral ramus (supplying ventrolateral body surface, body wall and limbs) • Each pair of nerves monitors one dermatome Nerve plexus • Complex interwoven network of nerves • Four large plexuses • Cervical plexus • Brachial plexus • Lumbar plexus • Sacral plexus Principles of Functional Organization General organization • Sensory neurons • Deliver information to CNS • Motor neurons • Distribute commands to peripheral effectors • Interneurons • Interpret information and coordinate responses Neuronal pools • Functional group of int
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