1. What structure most directly stimulates a skeletal muscle fiber to contract?

Question

1. What structure most directly stimulates a skeletal muscle fiber to contract?

a. Voltage-gated calcium channels

b. Acetylcholinesterase

c. Synaptic cleft

d. Motor neuron

2. Rank the sequence of events at the NMJ that initiate an action potential in the muscle fiber, from first to last.

- Action potential arrives at the axon terminal.

- Acetylcholine binds to its receptors on the junctional folds.

- Calcium ions enter the axon terminal.

- Synaptic vesicles fuse to membrane of axon terminal.

- Junctional folds become depolarized.

- Action potential is initiated on the sarcolemma.

- Acetylcholine is released into the synaptic cleft.

Explanation / Answer

1.b. Acetylcholinesterase

2.- Calcium ions enter the axon terminal

- Synaptic vesicles fuse to membrane of axon terminal.

- Acetylcholine is released into the synaptic cleft

- Acetylcholine binds to its receptors on the junctional folds

Junctional folds become depolarized

- Action potential arrives at the axon terminal

- Action potential is initiated on the sarcolemma

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