Question

What activation threshold must typically be reached for nerve depolarization (action potential) to occur?

a. -55 mV
b. -70 mV
c. 55 mV
d. 70 mV

Answer 1

The activation threshold for nerve depolarization to trigger an action potential is -55 mV, at which point voltage-gated Na+ channels open and the action potential begins.

Step-by-step explanation:

The activation threshold that must typically be reached for nerve depolarization (action potential) to occur is -55 mV. This is the value at which voltage-gated Na+ channels open, initiating the action potential. Reaching or exceeding this threshold leads to the all-or-none response characteristic of action potentials. If depolarization does not reach this threshold, no action potential will be generated. Once an action potential is initiated, it will propagate along the neuron, peaking at around +30 mV, which is a change of approximately 100 mV from the resting membrane potential.