motor units and movement Flashcards
somatic nervous system
A branch of the Peripheral nervous system which consists of the skeletal muscles and their neural control elements
muscle synergist
muscle that assists the primary movers
biceps brachii and brachialis work together. which muscle is the primary mover ?
biceps brachii
what muscles are antagonistic to biceps brachii and brachialis (as flexors)
triceps brachii and anconeus ( extensors )
Axial muscles
muscles that control movements of the trunk
proximal muscles
muscles that are found in the shoulder, elbow, pelvis and knee and the mediate locomotion
distal muscles
muscles that move the hands, feet and digits
where do upper motor neurons arise?
cerebral cortex
what neurotransmitter is used by the upper motor neurons ?
glutamate
where do the lower motor neurons arise from ?
spinal cord
what neurotransmitter is used by lower motor neurons
acetylcholine
how do lower motor neurons exit the spinal cord ?
in spinal nerves
motor unit
α motor neuron and all of the skeletal muscle that it innervates
motor pool
single muscle innervated by a group of α motor neurons
what influences the force of contraction from an α motor neuron ?
- motor unit recruitment
- frequency of action potentials generated
what do smaller motor units (small innervation ratio) control ?
finer movements (i.e. extraocular muscles of the eye )
what do larger motor units control
postural muscles (i.e. pectoralis and erector spinae)
how many motor neurons does a single muscle cell respond to ?
one
where do the cell bodies of lower motor neurons reside
ventral horn of the spinal cord
innervation ratio
the number of muscle fibers innervated by a single motor neuron
what type of movement are fast fatiguing motor units for
short bursts of power (powerlifting)
describe fast fatiguing motor units
-very high tension
- fatigues quickly
- large motor neurons and high AP threshold
- type IIx fibers
what type of movement are fatigue resistant motor units for
sustained locomotion (long distance running)
describe fatigue resistant motor units
-high tension
-intermediate α motor neuron and AP threshold
- type IIa fibers
describe slow motor units
-low tension
-fatigue resistant
- small α motor neurons and low AP threshold
- type I fibers
what is the oxidative capacity for slow muscle fibers vs fast muscle fibers
slow - high
fast - low
myoglobin in slow muscle fibers vs fast muscle fibers
slow - high
fast - low
glycolytic capacity in slow muscle fibers vs fast muscle fibers
slow - low
fast -high
myosin ATPase activity in slow muscle fibers vs fast muscle fibers
slow- slow
fast - fast
fatigue resistance in slow muscle fibers vs fast muscle fibers
slow - high
fast - low
what is the order of motor unit recruitment
1) slow motor units
2) fast fatigue-resistant
3) fast fatigable
(aka size principle)
what frequency is associated with twitch muscle contractions
5Hz
what frequency is associated with unfused tetanus muscle contractions
20Hz
what frequency is associated with wave summation muscle contractions
10Hz
what frequency is associated with fused tetanus muscle contractions
40Hz
fused tetanus
type of muscle contraction where there is no relaxation of the muscle fibers between stimuli
unfused tetanus
type of muscle contraction where the muscle fibers do not completely relax before next stimulus
wave summation
muscle fibers produce stronger contractions by being stimulated rapidly before they can fully relax, resulting in an increase force of contraction
twitch
single AP from a motor neuron that produces a single contraction in the muscle fiber
