in Discussion | a month ago

Overview of Spinal Cord • Information highway between brain and body • Extends through vertebral canal from foramen magnum to L1 • Each pair of spinal nerves receives sensory information and issues motor signals to muscles and glands • Spinal cord is a component of the Central Nervous System while the spinal nerves are part of the Peripheral Nervous System Functions of the Spinal Cord • Conduction – bundles of fibers passing information up and down spinal cord • Locomotion – repetitive, coordinated actions of several muscle groups – central pattern generators are pools of neurons providing control of flexors and extensors (walking) • Reflexes – involuntary, stereotyped responses to stimuli (remove hand from hot stove) – involves brain, spinal cord and peripheral nerves Anatomy of the Spinal Cord • Cylinder of nerve tissue within the vertebral canal (thick as a finger) – vertebral column grows faster so in an adult the spinal cord only extends to L1 • 31 pairs of spinal nerves arise from cervical, thoracic, lumbar and sacral regions of the cord – each cord segment gives rise to a pair of spinal nerves • Cervical and lumbar enlargements • Medullary cone (conus medullaris) = tapered tip of cord • Cauda equinae is L2 to S5 nerve roots resemble horse’s tail Meninges of the Spinal Cord • 3 Fibrous layers enclosing spinal cord • Dura mater – tough collagenous membrane surrounded by epidural space filled with fat and blood vessels • epidural anesthesia utilized during childbirth • Arachnoid mater – layer of simple squamous epithelium lining dura mater and loose mesh of fibers filled with CSF (creates subarachnoid space) • Pia mater – delicate membrane adherent to spinal cord – filium terminale and denticulate ligaments anchor the cord Nerve Plexuses • Ventral rami branch and anastomose repeatedly to form 5 nerve plexuses – cervical in the neck, C1 to C5 • supplies neck and phrenic nerve to the diaphragm – brachial in the armpit, C5 to T1 • supplies upper limb and some of shoulder and neck – lumbar in the low back, L1 to L4 • supplies abdominal wall, anterior thigh and genitalia – sacral in the pelvis, L4, L5 and S1 to S4 • supplies remainder of lower trunk and lower limb – coccygeal, S4, S5 and C0

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