Question

multiple choice question

when skeletal muscle contracts, ______ enzyme is released.

• acetylcholine
• antihistamine
• acetylcholinesterase
• antidiuretic hormone

Explanation:

Identify the biological context of the question

Using the Muscle Contraction, Neuromuscular Junction, and Acetylcholine knowledge points

• The question asks for the specific enzyme released or active during skeletal muscle contraction.
• At the neuromuscular junction, the neurotransmitter acetylcholine is released to initiate contraction.
• To allow the muscle to relax and prevent continuous stimulation, the neurotransmitter must be rapidly broken down.
• The enzyme responsible for degrading acetylcholine in the synaptic cleft is acetylcholinesterase.

Analyze the given options

• acetylcholine: This is a neurotransmitter (a chemical messenger), not an enzyme.
• antihistamine: This is a class of drugs used to treat allergies, not an endogenous enzyme involved in muscle contraction.
• acetylcholinesterase: This is an enzyme (indicated by the suffix "-ase") that breaks down acetylcholine at the neuromuscular junction.
• antidiuretic hormone: This is a hormone (also known as vasopressin) that regulates water balance in the kidneys, not an enzyme.

Answer:

• acetylcholine
• antihistamine
• acetylcholinesterase (Correct answer)
• antidiuretic hormone