PNS Flashcards
# pairs of spinal nerves are connected to the spinal cord
31
inner most layer that wraps individual axons within a nerve
endoneurium
groups of axons with their endoneurium are held together in bundles
fascicles
wraps around a fascicle (middle layer). Thick and contains up to 15 layers of fibroblasts within a network of collagen fibers
perineurium
outermost layer and covers the entire nerve (multiple fascicles with perineurium). extensions of the epineurium fill the spaces between fascicles
Epineurium
Lumbar, sacral, and coccygeal nerve roots descend from their point of origin at the ________ of the spinal cord
lower end
describes the appearance of the lower end of the spinal cord and its spinal nerves as a “horse’s tail”
Cauda equina
Each spinal nerve attaches to the spinal cord by a ______ root and a ______ root
ventral (anterior) root
Dorsal (posterior root)
All spinal nerves contain both motor and sensory fibers, making them ______.
mixed nerves
one of several large branches formed after each spinal nerve emerges from the spinal cavity
ramus
Each spinal nerve splits into a distinct _____ ramus and ____ ramus.
ventral, dorsal
supplies somatic motor and sensory fibers to several smaller nerves. These smaller nerves innervate the muscles and skin of the posterior surface of the head, neck, and trunk.
dorsal ramus
motor (autonomic and somatic) and sensory fibers innervate muscles and glands in the extremities and in the lateral and ventral portions of the neck and trunk
ventral ramus
autonomic motor fibers split from the ventral ramus and head toward a ganglion of the ________.
sympathetic chain
complete networks formed by the ventral rami of most spinal nerves (not T2-T12) subdividing and then joining together to form individual nerves
nerve plexuses
