Intro to PNS: Spinal Cord and Spinal Nerve

Question 1

gray matter

Answer 1

seat of neurons (cell bodies) w/in the spinal cord. this portion is unmyelinated.

Question 2

dorsal horn

Answer 2

composed of neurons that give rise to fibers that complete simple reflex arcs, decussates (cross to the opposite side) or ascend to other sensory substation in the CNS

Question 3

lateral horn

Answer 3

intermediolateral cell column (IMLCC)

- contains automatic pre-ganglionic neurons that innervate smooth muscle.

Question 4

ventral horn

Answer 4

contains neurons whose fibers innervate skeletal muscle

Question 5

white matter

Answer 5

composed of ascending and descending fiber tracts grouped in funiculi (fiber bundles), composed of smaller fascicli.

Question 6

dorsal root

Answer 6

for the most part, transmits afferent (sensory) fibers of somatic and visceral origins

Question 7

ventral root

Answer 7

for the most part transmits efferent (motor)fibers to somatic and visceral structures

Question 8

spinal (segmental) nerves

Answer 8

a mixed nerve (motor and sensory) formed at the junction of a dorsal and ventral root.

Question 9

dorsal primary ramus

Answer 9

dorsal branch of spinal nerve containing fibers of all types (sensory, motor, somatic, visceral) which innervate cutaneous and subcutaneous areas of the dorsal surface of the head, neck and trunk, deep back muscles, and joints of the spine

Question 10

ventral primary ramus

Answer 10

ventral branch of a spinal nerve containing fibers of all types which innervate the limbs and ventral torso; form all somatic nerve plexuses of the body (cervical, brachial, and lumbosacral

Question 11

name the types of fibers found in the spinal nerves.

Answer 11

somatic afferent, visceral afferent

somatic efferent, visceral efferent

Question 12

segmental innervation

Answer 12

result of early contact between developing nerve fibers and what will eventually become their peripheral targets

Question 13

dermatome

Answer 13

area of skin innervated by cutaneous branches of a single spinal nerve. when combined with other areas gives rise to the dermatome map which can be used to determine which possible nerves may have been damaged during an injury.

Question 14

nerve plexus

Answer 14

‘network of intersecting nerves’ - combining, mixing and branching of nerves such that fibers of up to 3 or 4 dorsal roots supply each dermatome and muscles. makes it so that if a nerve is severed it cannot ablate an entire dermatome or paralyze an entire muscle.