Question

An individual has just ingested a chemical that binds irreversibly to the ACh receptors in the sarcolemma. By itself it does not alter membrane potential, yet prevents normal neurotransmitter binding. Ignoring the effects on any other system, the consequence to skeletal muscle would be ________?

1) irreversible contraction as soon as the first nervous stimulation reached the sarcolemma
2) no contraction at all by nervous mechanisms
3) contraction if stimulated by an external electrode
4) no contraction at all by nervous mechanisms, but contraction if stimulated by an external electrode

Answer 1

The consequence to skeletal muscle when a chemical binds irreversibly to ACh receptors is no contraction by nervous mechanisms, but contraction with external electrode stimulation.

Step-by-step explanation:

The consequence to skeletal muscle when an individual ingests a chemical that binds irreversibly to the ACh receptors in the sarcolemma and prevents normal neurotransmitter binding would be no contraction at all by nervous mechanisms, but contraction if stimulated by an external electrode.

The chemical that binds irreversibly to the ACh receptors in the sarcolemma prevents the binding of acetylcholine (ACh), which is the neurotransmitter responsible for muscle contraction. Without ACh binding to the receptors, the muscle fibers cannot be stimulated to contract by the nervous system. However, if an external electrode is used to directly stimulate the muscle fibers, muscle contraction can still occur.