motor units Flashcards
what is a motor unit
A motor unit consists of a motor neuron AND a number of muscle fibres.
what is a motor neurone
Motor neurons are specialised cells which transmit nerve impulses to a group of muscle fibres
when can skeletal muscles contract
only contract when stimulated by an electrical impulse, sent from the Central Nervous System which travels down the extending axon which connects to the motor end plates
what is the place called where the axon’s motor end plates meet the muscle fibre
neuromuscular junction
what is the action potential
refers to a positive electrical charge inside the motor unit, which conducts the nerve impulse down the neuron into the muscle fibre.
what happens when a motor unit receives stimulus
creates an action potential that reaches or is above the threshold charge
what happens to the muscles during the threshold of charge
aLL the muscle fibres within that motor unit will contract at the same time and with maximum force
what happens when the charge does not reach the threshold
no muscle fibres contract
what is the small gap between between the motor end and muscle fibres called
synaptic cleft
what is the neurotransmitter and what does it do
acetylcholine (Ach) it transfers the electrical charge across the cleft
if their is enough neurotransmitter secreted and enough charge what happens.
muscle action potential is created
after the muscle action is created what happens in the muscles
a wave of contraction goes down the muscle fibre
what is the all or none law
‘When stimulated ALL the
Fibres within a motor unit
Contract completely or not
at all.’
