Motor control (big ppt) Flashcards
What is muscle tone?
The degree of contraction of a muscle or the proportion of motor units that are active at any one time
What is high and low muscle tone?
High tone - feels firm or rigid; it resists passive stretch
Low tone - feels soft or flaccid
How does alpha motor neuron activity alter when relaxed and contracted?
- Relaxed: alpha motor neuron activity does not make a significant contribution to the resistance to stretch
- Alert: more activation of the alpha motor neurons occur and muscle tone increases
What is EPP?
End plate potential
How does a single EPP compare to a single EPSP?
A single EPP is larger than a single EPSP as the neurotransmitter is released over a larger surface area
Describe the process for neuromuscular junction?
- Action potential in a motor neuron arrives at the axon terminal and depolarises the plasma membrane
- Voltage-gated Ca2+ channels open and calcium ions diffuse into the axon terminal
- Calcium binds to proteins which allows the Ach vesicles to fuse with the neuronal plasma membrane
- Ach diffuses to motor end plate and binds to cholinergic nicotinic receptors
- This opens an ion channel in the receptor protein resulting in more Na+ moving in than K+ out so an EPP is produced (contraction)
What is the neurotransmitter involved with UMN?
Glutamate
Where is the cell body of an UMN?
Cerebral cortex or brainstem
Where is the cell body of LMN?
Ventral horn of the spinal cord or the brainstem motor nuclei
What do alpha- motor neurons of the LMN do?
- Cause contraction of the muscle fibres
- Produce clinical signs of LMN syndrome when damaged
- Somatotopically organised
What do the y-motor neurons of the LMN do?
- Regulation of muscle tone and maintaining proprioception
- Signal length and velocity of a muscle
