Question

the axon terminal releases acetylcholine into the synaptic cleft, which is received by

a sarcomere
the varicosity of a smooth muscle cell
the thick filament
the neuromuscular junction of a skeletal muscle
a motor unit

Explanation:

Identify the key physiological process

The question describes the release of acetylcholine (ACh) from an axon terminal into the synaptic cleft.

Analyze the target receptor site

ACh is a neurotransmitter that binds to receptors on the postsynaptic membrane.

Evaluate the given options

• A sarcomere is the basic contractile unit inside a muscle fiber, not a direct receiver at the synaptic cleft.
• Varicosities are neurotransmitter-releasing sites in smooth muscle, not the receiving end of this specific somatic motor pathway.
• Thick filaments are intracellular contractile proteins (myosin).
• The neuromuscular junction (specifically the motor end plate of a skeletal muscle) contains the nicotinic ACh receptors that receive the released neurotransmitter.
• A motor unit consists of a motor neuron and all the muscle fibers it innervates, which is a broader structural organization.

Select the correct option

The neuromuscular junction of a skeletal muscle is the specific site where the axon terminal meets the muscle fiber to receive acetylcholine.

Answer:

• A sarcomere
• The varicosity of a smooth muscle cell
• The thick filament
• The neuromuscular junction of a skeletal muscle (Correct answer)
• A motor unit