Question

q4.8. which statement below is true about the voltage - gated na⁺ channels during the action potential? the voltage - gated na⁺ channels are open the entire time that the neuron is depolarized (when vm is above resting potential). the voltage - gated na⁺ channels open after the voltage - gated k⁺ channels. the voltage - gated na⁺ channels open to restore vm to the resting potential after the action potential peak. the voltage - gated na⁺ channels are open when vm is rapidly increasing during the action potential.

Explanation:

During an action potential, when the membrane potential ($V_m$) reaches the threshold, voltage - gated Na⁺ channels open rapidly, allowing Na⁺ ions to rush into the cell and causing a rapid increase in $V_m$. They do not stay open throughout depolarization, open before voltage - gated K⁺ channels, and it is the opening of voltage - gated K⁺ channels that helps restore $V_m$ to the resting potential after the action potential peak.

Answer:

The voltage - gated Na⁺ channels are open when $V_m$ is rapidly increasing during the action potential.