Question

click and drag on elements in order
list the events leading to excitation of a muscle fiber in order, starting at the top.
instructions
the permeability of sarcolemma to sodium ions increases.
nerve impulse arrives at a distal end of the axon.
acetylcholine binds to its receptors on the muscle fiber sarcolemma.
acetylcholine diffuses across the synaptic cleft.
acetylcholine is released.

Explanation:

Muscle fiber excitation starts with a nerve - impulse arrival. This leads to acetylcholine release, which then diffuses across the synaptic cleft and binds to receptors on the sarcolemma. This binding increases the sarcolemma's sodium - ion permeability.

Answer:

1. Nerve impulse arrives at a distal end of the axon.
2. Acetylcholine is released.
3. Acetylcholine diffuses across the synaptic cleft.
4. Acetylcholine binds to its receptors on the muscle fiber sarcolemma.
5. The permeability of sarcolemma to sodium ions increases.