- Neuromuscular Junctions
- the point where a motor neurone meets a skeletal muscle fibre.
- they are spread throughout the muscle, ensuring that the contraction of the muscle is rapid and powerful when it is simultaneously stimulated by action potentials.
- all muscle fibres supplied by a singular motor neurone acts together as a single functional unit and are known as motor-units.
- motor-units give control over the force that the muscle exert; if only a small force is needed, only a few units are stimulated, if a larger force is needed then more units are stimulated.
- when a nerve impulse is received at the neurotransmuscular junction, the synaptic vesicles fuse with the presynaptic membrane and release their acetylcholine, which diffuses to the post synaptic membrane, altering its permeability to sodium ions, which enter rapidly depolarising its membrane.
- the acetylcholine is broken down into choline and ethonic acid by acetylcholinsterase, to ensure the muscle is not over stimulated.
- choline and ethonic acid diffuses back to the presynaptic membrane, where ATP from the mitochondria, recombines it to acetylcholine.