motor units and movement Flashcards
what is the somatic nervous system
a branch of the peripheral nervous system which consists of the skeletal muscle and their neural control elements
voluntary
what is the function of the axial muscles
control movements of the trunk
what is the function of the proximal muscles
mediate locomotion
found in the shoulder, elbow, pelvis and knee
what is the function of the distal muscles
move the hands, feet and digits
what is the anatomy of the somatic nervous system
consists of upper motor neurons and lower motor neurons
what are upper motor neurons
arise in the cerebral cortex - CNS in the brain
uses glutamate as a neurotransmitter
what are lower motor neurons
arise from the spinal cord - axons synapse directly on skeletal muscle > force generation
uses acetylcholine as a neurotransmitter
what is the anatomy and organisation of the lower motor neurons
exit the spinal cord in spinal nerves
provide both motor and sensory supply to skeletal muscle, and sensory input from skin and visceral receptors
30 spinal nerves which innervate muscles roughlt at the spinal segment
what is a motor unit
⍺-motor neuron and all of the skeletal muscle it innervates
what is a motor pool
single muscle innervated by a group of ⍺-motor neurons
how is the force of contraction from an ⍺-motor neuron influenced
motor unit recruitment
frequency of action potential generated
what are the features of motor units
motor units vary in size
smaller motor units control finer movements e.g. extraocular muscles of the eye - innervated by smaller ⍺-motor neurons
larger motor units control postural muscles e.g. pectoralis and erector spinae - innervated by larger ⍺-motor neurons
what is the twitch response in skeletal muscle fibre
red muscle - slow
white muscle - fast
what is the myosin ATPase activity in skeletal muscle fibre
red muscle - slow
white muscle - fast
what is fatigue resistance in skeletal muscle fibre
red muscle- high
white muscle - low
what is the oxidative capacity in skeletal muscle fibre
red muscle - high
white muscle - low
what is myoglobin in skeletal muscle fibre
red muscle - high
white muscle - low
what is the glycolytic capacity in skeletal muscle fibre
red muscle - low
white muscle - high
what are the types of motor units
fast fatiguing
fatigue resistant
slow
what are the characteristics of fast fatiguing motor units
very high tension
fast fatiguing
large ⍺-motor neuron, high threshold
type IIx fibres
‘burst power’
what are the characteristics of fatigue resistant motor units
high tension
slow fatiguing
intermediate ⍺-motor neuron, and threshold
type IIa fibres
‘sustained locomotion’
what are the characteristics of slow motor units
low tension
fatigue resistant
small ⍺-motor neuron, low threshold
type I fibres
‘antigravity, sustained movement’
what is motor unit recruitment
the greater the number of motor units which can be recruited increases the force of contraction that a muscle can produce
fixed order of recruitment in response to increasing activity of the lower motor neurons stimulating the muscle (the motor pool)
> starts with slow motor units, then, fast, fatigue-resistant units, finally fast, fatigable units
also known as the size principle
