spinal cord tracts and nerves lecture two part two

spinal cord tracts

bundles of axons that run in the white matter of the spinal cord

types of spinal cords

ascending tracts and descending tracts

ascending tracts

sensory axons that travel from body to brain

descending tracts

motor axons that travel from brain to body

what is a nerve

a structure you can see with the naked eye and formed by many axons bundled together in ct wrappings

connective tissues in spinal cord

endoneurium, perineurium, epineurium (inner to outer)

how is a spinal nerve formed

from the unification of anterior and posterior roots

anterior roots

axons of motor neurons

posterior roots

axons of sensory neurons

posterior root ganglions

contain cell bodies of sensory neurons

spinal nerve branches (rami)

posterior ramus, anterior ramus

posterior horns

innervates deep back muscles and skin of back, smaller

anterior ramus

innervates everything else from the neck inferiorly, larger and performs nerve plexuses

plexus

networks of converging or diverging axons

rami vs roots

roots are organized by function (sensory or motor)

rami are organized by location (posterior, anterior)

dermatomes

segments of skin innervated by a single spinal nerve; create a sensory map of the body

shingles

chicken pox virus that lies dormant in posterior root ganglion, reactivates along dermatomes as shingles