Motor Units and Movement

Question 1

anatomy of upper motor neurons

Answer 1

arise in cerebral cortex and extend down spinal cord
use glutamate as neurotransmitter

Question 2

anatomy of lower motor neurons

Answer 2

arise from spinal cord and extend to muscle
use ACh as neurotransmitter

Question 3

function of lower motor neurons

Answer 3

provide both motor and sensory supply to skeletal muscle
sensory input from skin and visceral receptors

Question 4

what is a motor unit

Answer 4

alpha motor neuron ad all of the skeletal muscle it innervates

Question 5

what is a motor pool

Answer 5

single muscle innervated by a group of alpha motor neurons

Question 6

what factors contribute to the force of contraction of a motor pool

Answer 6

motor unit recruitment
frequency of APs generated

Question 7

how is fine muscle control achieved

Answer 7

recruitment of many motor units

Question 8

what do smaller motor units control
what innervates them

Answer 8

finer movements (i.e. muscles of the eye)
small alpha motor neurons

Question 9

what do larger motor units control
what innervates them

Answer 9

postural muscles (i.e. pectoralis or erector spinae)
larger alpha motor neurons

Question 10

what dictates if a muscle will be slow or fast twitch

Answer 10

how quickly they release ATP to form cross-bridges and the source of the ATP used (glycolysis vs oxphos)

Question 11

in which order are different motor unit types recruited

Answer 11

slow motor units
fast fatigue-resistant units
fast fatigable units
(size principle)