motor units and movement Flashcards
biceps branchii and what work together
branchialis
biceps and triceps working with and against each other
Biceps brachii and brachialis (as flexors) oppose-triceps brachii and anconeus (as extensors),these groups are antagonists to each other
what does axial muscle control
movements of the truk
What are proximal muscles found
in the shoulder, elbow, pelvis and knee
what do distal muscles move
hands, feet and digits
Motor neurons of the somatic nervous system
→ Upper motor neurons
→ Lower motor neurons
upper motor neurons
→ Arise in the cerebral cortex
→ Use glutamate as a neurotransmitter
Lower motor neurons
→ Arise from the spinal cord
→ Use acetylcholine as a neurotransmitter
what do lower motor neurons exiting the spinal cord in the spinal nerves do
→ Provide both motor and sensory supply to skeletal muscle (and sensory input from skin, visceral receptors, too)
motor unit
a motor neuron and all of the skeletal muscle innervates
Motor pool
single muscle innervated by group of α motor neurons
A force of contraction from α motor neuron influenced by
→ Motor unit recruitment
→ Frequency of action potentials generated
what do small motor units control
finer movements (i.e. extraocular muscles of the eye)
what do larger motor units control
postural muscles (i.e. pictorials and erector spine)
like posture
properties of fast-fatiguing muscles
- Very high tension
- Fast fatiguing
- Large α-MN,high threshold
- Type IIx fibres
properties of fatigue-resistant muscles
- High tension
- Slow fatiguing
- Intermediate α-MNand threshold
- Type IIa fibres
properties of slow muscles
- Low tension
- Fatigue resistant
- Small α-MN,low threshold
- Type I fibres
what can increase the force of contraction that a muscle can produce
greater number of motor units
Fixed order of recruitment in response to increased 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
summary
The somatic nervous system is responsible for motor control of skeletal muscle
That control is facilitated by upper motor neurons which synapse on and drive lower motor neurons which act as the final common pathway in initiating skeletal muscle contraction
Lower motor neurons exit the spinal cord as spinal nerves and are organized into motor units with skeletal muscle fibres
The force of contraction of skeletal muscle can be modulated by:
→ Motor unit recruitment
→ Changes in the frequency of action potentials generated
