Question

As an axon enters a muscle, it branches into a number of axonal terminals, each of which forms a neuromuscular junction with a single muscle fiber. A motor neuron and all the muscle fibers it supplies is called a

a. neuromuscular junction
b. synaptic cleft
c. synaptic knob
d. motor unit
e. motor end plate

Answer 1

A motor unit is a motor neuron and all the muscle fibers it supplies. Each motor neuron forms a neuromuscular junction with a single muscle fiber. The release of acetylcholine at the neuromuscular junction initiates muscle contraction.

Step-by-step explanation:

A motor unit consists of a motor neuron and all the muscle fibers it supplies. Each motor neuron branches into several axonal terminals, each of which forms a neuromuscular junction with a single muscle fiber. The neuromuscular junction is a specialized synaptic structure where the axon terminal of the motor neuron connects with the muscle fiber's sarcolemma. The motor neuron releases the neurotransmitter acetylcholine, which binds to receptors on the sarcolemma, initiating muscle contraction.