Specifically, the neurotransmitter responsible for this communication is acetylcholine (ACh). Here's how it works:
1. Action Potential: An electrical signal called an action potential travels down the motor neuron axon.
2. Synaptic Vesicle Release: When the action potential reaches the end of the axon (the axon terminal), it triggers the release of acetylcholine-filled synaptic vesicles.
3. Synaptic Cleft: These vesicles fuse with the presynaptic membrane and release acetylcholine into the synaptic cleft, the space between the motor neuron and muscle fiber.
4. Muscle Fiber Stimulation: Acetylcholine diffuses across the synaptic cleft and binds to receptors on the muscle fiber's membrane (the sarcolemma).
5. Muscle Contraction: This binding initiates a series of events within the muscle fiber, ultimately leading to muscle contraction.
So, in essence, the motor neuron sends a chemical message (acetylcholine) to the skeletal muscle, causing it to contract.
