When a depolarizing graded potential makes the axon membrane depolarize to threshold,
A)ligand-gated Ca⁺² channels close rapidly.
B)voltage-gated Ca⁺² channels open rapidly.
C)ligand-gated Na⁺ channels close rapidly.
D)voltage-gated Na⁺ channels open rapidly.
E)none of these choices occur.

Question

Quizplus · Accepted Answer

When a depolarizing graded potential makes the axon membrane depolarize to threshold, voltage-gated Na+ channels open rapidly, allowing an influx of Na+ ions and leading to the initiation of an action potential. Ligand-gated Ca²+ channels may play a role in neurotransmitter release at the axon terminal, but they are not directly involved in the generation of an action potential. Ligand-gated Na+ channels do not exist in axon membranes - only voltage-gated Na+ channels are involved.

When a Depolarizing Graded Potential Makes the Axon Membrane Depolarize