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primary communication link between the brain and the peripheral nervous system, integration of incoming info, reflex mechanisms, form foramen magnum to L2
31 pairs, exit the vertebral column through the intervertebral and sacral foramina, not uniform in diameter
Cervical and Lumbosacral Enlargements
larger diameter of cord, give rise to the spinal nerves of the limbs
cone like region of the spinal cord inferior to the lumbosacral enlargement, have caudal equina off of it
form a thecal sac that surrounds the spinal cord, attaches to the rim of the foramen magnum and ends at the level of the second sacral vertebra, most superior
between the periosteum of the vertebral canal and the dura mater, contains blood vessels, areolar tissue and fat
consist of myelinated axons forming tracts, located peripherally, organized into three columns ventral, dorsal, lateral
composed of axons ascending to the brain or desending from the brain, axons within carry same type of info
spinal nerves arise as rootlets then combine to form roots, located along the dorsal and ventral surfaces of the spinal cord
basic functional unit of the nervous system, simplest portion capable of receiving a stimulus and producing a response, stereotypic, unconscious, and involuntary responses to stimuli, maintains homeostasis
mediated through the somatic motor nervous system, responses; remove for painful stimuli, keep from falling suddenly, cause movement because of external forces
mediated through the autonomic nervous system, responsible for maintaining variables within their normal ranges; blood pressure, carbon dioxide levels, water intake
muscles contract in response to a stretching force applied to them, innervated by specific motor neurons, sensory neurons innervate the non contractile centers of the muscle spindle cells, synapse with alpha motor neurons, and intern innervate the muscle with spindle
Golgi Tendon Reflex
reflex preventing contracting muscles from applying excessive tension to tendons, prevents damage to tendons, produces sudden relaxation of muscles
Golgi Tendon Organ
encapsulated nerve endings that have at their ends numerous terminal branches with small swelling associated with bundles of collagen fibers in tendon, located in tendon near muscle
reflex function to remove a body limb from a painful stimulus, have reciprocal innervation and crossed extensor reflex
causes relaxation of extensor muscle when flexor muscle contracts in withdrawal reflex, also involved in stretch reflex
Crossed Extensor Reflex
when a withdrawal reflex is initiated in one lower limb, the crossed extensor reflex causes extension of opposite lower limb
Spinal Nerve Structure
consist of axon bundles, schwann cells and connective tissue, have endoneurium, perineurium and epineurium layers
branches of nerves that innervate deep muscles of the trunk responsible for movements of the vertebral column and the CT and skin near the midline of the back
branches of nerve, what they innervate depends on what part of the spinal cord is considered
part of ventral ramus, form intercostal nerves that innervate the intercostal muscles and the skin over the thorax
C1-C4 innervate superficial neck, structures, skin of neck, posterior portion of head, have ansa cervicalis, and phrenic nerve
in cervical plexus, C3-C5, part of both cervical and brachial plexus, innervates diaphragm
C4, C5-T1, five ventral rami form three trunks, separate into six divisions of cords giving rise to beaches/nerves; axillary, radial, musculocutabeous, ulnar, median, and small nerves that innervate muscles action on scapula and arm
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