Upon preventing acetylcholine from diffusing across a neuromuscular junction, which of the following will occur?
Correct answer: A. No action potential will be produced in the affected muscle fibres.
- A. No action potential will be produced in the affected muscle fibres.
- B. The endoplasmic reticulum releases calcium ions (Ca2++) into the cytoplasm.
- C. Myosin will bind to actin in the affected muscle fibre.
- D. The affected muscle fibre will contract.
Explanation
Acetylcholine is a vital neurotransmitter at the neuromuscular junction, responsible for starting the cascade of events leading to muscle contraction. When acetylcholine is blocked from diffusing, it cannot bind to receptors on the muscle cell membrane, preventing the initiation of an action potential. As a result, the muscle fibre remains inactive and does not contract. Other processes such as calcium ion release and myosin-actin interaction are contingent on the presence of an action potential, which is absent in this scenario, rendering options B, C, and D incorrect.
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About Muscle Contraction
Muscle contraction is explained by the sliding filament model, in which myosin heads pull actin filaments within sarcomeres using ATP. The topic covers calcium, troponin, tropomyosin, the neuromuscular junction and relaxation, with attention to how filament length stays almost constant while the sarcomere shortens.
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