physiology exam 2 questions from review

Question 1

upper motor neurons

Answer 1

descend the spinal cord to level of the of the appropriate spinal nerve root and synapse with lower motor neuron or interneuron

Question 2

what is the neurotransmitter of upper motor neuron and lower motor neuron

Answer 2

glutamate (binds to glutamergic receptors)

Question 3

lower motor neuron: where are they found? where do they terminate?

Answer 3

typically found in anterior gray portion of the spinal cord or cranial nerve nuclei of brandstem
teminate at effector

Question 4

neurotransmitter of lower motor neuron

Answer 4

acetylcholine

Question 5

where are renshaw cells found?

Answer 5

anterior horns of spinal cord

Question 6

function of renshaw cells

Answer 6

transmit inhibitory signals to surounding motor neurons resulting in lateral inhibition and enhance the fluidity of limb movement
transmits inhibitory signal to collateral branch of alpha motor neuron that it receives: recurrent inhibition/ negative feedback

Question 7

list possible sensory fibers

Answer 7

A-alpha, A-beta, A-delta, or C fibers

Question 8

order the sensory fibers in terms of conductance rate

Answer 8

A-alpha and A-beta (30-120 m/sec.) > A-delta (4-30 m/sec) > C fibers (<2.5 m/sec)

Question 9

what type of fibers compose nociceptors and thermoreceptors

Answer 9

C fiber or A-delta fibers

Question 10

how long is a muscle spindle

Answer 10

3-10 mm long

Question 11

what type of neuron innervates muscle spindles

Answer 11

small gamma motor neurons (group II afferents)

Question 12

describe a muscle spindel

Answer 12

3-12 intrafusal fibers encapsulated within a sheath and run parallel to extrafusal fibers
detects changes in muscle length

Question 13

the number of muscle spindles increase or decrease with finer movements?

Answer 13

increase

Question 14

how does the central region of a muscle spindle differ than the rest of the spindle?

Answer 14

it has no contractile fibers and acts as a sensory receptor
where sensory fibers originate
stretching of central region intrafusal fiber stimulates sensory fibers
when stimulate, they stimulate alpha-motor neurons, resulting in contraction and shortening of muscle

Question 15

what type of fibers make up muscle fibers and what are they innervated by

Answer 15

extrafusal fibers

alpha motor neuron

Question 16

what are the two types of intrafusal fibers, which are more prominent

Answer 16

nuclear bag fibers and nuclear chain fibers

nuclear chain fibers are more prominent

Question 17

nuclear bag fibers: function, innervation

Answer 17

detect rate of change in muscle length
innervated by group Ia afferents and dynamic gamma efferents

(have multiple nuclei located in a central “bag-like” configuration)

Question 18

nuclear chain fibers: function, innervation

Answer 18

detect static change in muscle length
innervated by group II affernt and static gamma efferents

(multiple nuclei arranged in a single row)

Question 19

what sensory fibers are in the central region of intrafusal fibers in the muscle spindle

Answer 19

Ia (primary fibers) and II (secondary fibers)

Question 20

what areas of the brain control gamma fibers

Answer 20

bulboreticular region of brain stem, crebellum, basal nuclei, cerenr