HY from lecture 10

Question 1

what is a motor unit?

Answer 1

a group of muscle fibers innervated by a single lower motor or _alpha neuron _

Question 2

what is size of motor neuron proportional to? what does contraction strength approximate? what does fine control regulate?

Answer 2

1. size of motor neuron is ~ to the # of muscle fibers innervated.
2. contraction strength ~ motor unit size
3. fine cotnrol regulated by small motor unit muscle pools

Question 3

what are type I muscle?

2. # of mitochondria, how do they fatigue and what type of contraction produced?
3. waht type of metabolism

Answer 3

Slow muscle with:

1. slow motor units
2. many mitochondria, capillary/myoglobin rich(red muscle)
3. fatigue slowly and produce slow, sustained(tonic) contractions
4. primary aerobic metabolism

Question 4

type II

1. what type of motor units?
2. amt of myoglobin, mitochondria and capillaries, type of contractions
3. what type of metabolism

Answer 4

type II

1. fast fatigable with large motor units.
2. muscle fibers sparse in myoglobin, mitochondria and capillaries (white muscle) and fatigue quickly, produce quick, forceful contractions.
3. primarily glycolytic (non-aerobic) metabolism

Question 5

what is the function of muscle spindles?

Answer 5

to facilitate the muscle stretch reflex and help maintain normal muscle tone

Question 6

what are gamma motor neurons motor to?

Answer 6

motor to intrafusal fibers

Question 7

gamma motor neuron activity reflects positive bias or gain on muscle tone. the higher the gain the greater the _1___ and _____2___

3. what alters gamma motor neuron gain?

Answer 7

1. muscle tone
2. force of contraction
3. local reflex circuitry and upper motor neuron input

Question 8

1. what do golgi tendon organs monitor?
2. which two structures povide input to alter golgi tendon organ activity

Answer 8

1. golgi tendon organs monitor muscle tension and protect the muscle against excessive contraction
2. local sensory circuitry and upper motor neourn input

Question 9

define upper motor neuron

Answer 9

motor neuron contained entirely in CNS (no part leavesthe CNS)

Question 10

lower motor neuron definition

Answer 10

neuron with cell body in the CNS projecting its axon into the PNS to innervate skeletal muslce