Acetylcholine released into the junction between a motor neuron and a skeletal muscle binds to a sodium/potassium channel and opens it. This is an example of ________.

Question

BlackTom AI · Accepted Answer

When examining how acetylcholine operates at the neuromuscular junction, several possibilities come to mind about channel types.
Option 1: 'a chemical that inhibits action potentials' describes a molecule that would reduce excitability, not a channel opening mechanism. It does not specify a type of ion channel and mischaracterizes the role of acetylcholine in this synapse.
Option 2: 'a ligand-gated channel' correctly identifies the mechanism: acetylcholine acting as a ligand binds to a receptor that directly gates the channel, allowing Na+ (and sometimes Ca2+) to pass and depolarize the muscle membrane.
Option 3: 'a voltage-gated channel' would open in response to changes in membrane potential, not directly in response to a chemical messenger binding. This description does not match how acetylcholine influences the postsynaptic membrane at the motor end plate.
Option 4: 'a second-messenger-gated channel' implies opening via intracellular signaling cascades triggered by receptors that are not themselves ion channels. In the neuromuscular junction, the receptor-channel is itself an ion channel that opens directly upon ligand binding, rather than via a second messenger system.
Overall, the key distinction is whether the signal directly gates the channel (ligand-gated) versus requiring voltage changes or intracellular messengers; the acetylcholine effect here is a direct ligand-gated channel opening, leading to depolarization of the muscle cell.

Acetylcholine released into the junction between a motor neuron and a skeletal muscle binds to a sodium/potassium channel and opens it. This is an example of ________.单项选择题

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