A specialised synapse
A neuromuscular junction is a specialised synapse between a motor neurone and a muscle cell.
The motor neurone forms the presynaptic cell, while the muscle cell forms the postsynaptic cell. The two cells are separated by a synaptic cleft.
The motor-neurone axon ends in a synaptic knob on the presynaptic side. This contains synaptic vesicles carrying acetylcholine.
- The motor-neurone axon ends in a synaptic knob on the presynaptic side.
- Synaptic vesicles contain the neurotransmitter acetylcholine (ACh).
- The synaptic cleft separates the motor neurone from the muscle cell.
- The muscle-cell membrane is the sarcolemma.
- The sarcolemma contains receptor proteins that bind ACh.
- The muscle cell contains myofibrils and mitochondria within its sarcoplasm.
The postsynaptic membrane at a neuromuscular junction is folded. This is one of the structural differences between a neuromuscular junction and the cholinergic synapse compared later in this note.