Question

Which of the following must be true of the structures of axons and muscle cells in order for nerve impulses to stimulate muscle contraction?

Answer 1

Motor neuron axons must connect to muscle fibers at a neuromuscular junction, acetylcholine must be released and bind to receptors on the sarcolemma, and depolarization of the sarcolemma must occur to initiate muscle contraction.

Step-by-step explanation:

In order for nerve impulses to stimulate muscle contraction, certain structures of axons and muscle cells must be true:

1. Motor neuron axons connect to muscle fibers at a neuromuscular junction: This is a specialized synaptic structure where the axon terminals of motor neurons synapse with the muscle fiber sarcolemma.
2. Acetylcholine is released and binds to receptors on the sarcolemma: The synaptic end bulbs of the motor neurons secrete acetylcholine, which binds to receptors on the muscle fiber sarcolemma, causing an increase in movement of cations.
3. Depolarization of the sarcolemma initiates muscle contraction: The binding of acetylcholine opens ligand-gated ion channels, which depolarizes the sarcolemma and triggers muscle contraction.

Answer 2

The following statement about the structures of axons and muscle cells in order for nerve impulses to stimulate muscle contraction must be true: Axons must have structures that make and secrete molecules, and muscle cells must have receptors that recognize these molecules. The axon conducts electrical impulses (action potentials) away from the nerve cell body.