Ch 3: Clinical Correlates pg 61-65

Question 1

what does the dorsal horn consist of?

Answer 1

laminae I-VI and neurons derived from alar plate which respond to sensory inputs provided mainly by dorsal roots of spinal nerves

Question 2

what does the ventral horn consist of?

Answer 2

laminae VIII-IX and cell bodies of alpha and gamma motor neurons which innervate skeletal muscle

Question 3

what does the intermediate zone consist of?

Answer 3

lamina VII: preganglionic autonomic neuron cell bodies (lateral horn T1-L2) and neuron cell bodies in Clarke’s nucleus (dorsal spinocerebellar tract to provide proprioceptive input to cerebellum from lower limbs)

Question 4

medial division dorsal root fibers: velocity, myelination, diameter, sensitivity to anoxia/anesthesia?

Answer 4

fastest-conducting
heavily myelinated
largest-diameter afferent fibers
most sensitive to anoxia
most resistant to anesthesia

Question 5

lateral division dorsal root fibers: velocity, myelination, diameter, sensitivity to anoxia/anesthesia?

Answer 5

slowest-conducting
thinly myelinated
smallest-diameter afferent fibers
more resistant to anoxia
most sensitive to anethesia

Question 6

what are the medial division dorsal root fibers?

Answer 6

Class Ia, Ib, Class II, A-beta fibers

Question 7

what are the lateral division dorsal root fibers?

Answer 7

A-delta, C fibers

Question 8

where do Class Ia and Ib fibers arise from?

Answer 8

muscle spindles (skeletal muscles: change in length/rate of change in length) and GTO (tendons: muscle force)

Question 9

where do Class II fibers arise from?

Answer 9

muscles spindles/joint receptors (muscle stretch and joint angle)

Question 10

where do A-beta fibers arise from?

Answer 10

mechanoreceptors in skin

Question 11

where do A-delta fibers arise from?

Answer 11

free nerve endings (skin) that respond to modalities of sharp pain and cold

Question 12

where do C fibers arise from?

Answer 12

free nerve endings (skin) that respond to dull/burning pain and warmth

Question 13

what are the three types of motor fibers which exit the spinal cord, and where do they do so?

Answer 13

• alpha, gamma: ventral root from all spinal cord segments

- preganglionic autonomic: from ventral roots of T1-L2 and S2-S4

Question 14

list motor fiber types in order of velocity and diameter from fastest to slowest; greatest to smallest

Answer 14

alpha
gamma
preganglionic autonomic

Question 15

what do alpha motor fibers innervate and what is their function?

Answer 15

extrafusal skeletal muscle fibers–>contracts a motor unit

Question 16

what do gamma motor fibers innervate and what is their function?

Answer 16

muscle spindles (intrafusal fibers)–>increases sensitivity of spindles to rate of stretch and change in muscle length

Question 17

what do preganglionic autonomic fibers innervate?

Answer 17

postganglionic autonomic cell bodies–>which go to smooth muscle autonomic glands, cardiac muscle