Final answer:
The K+ channel protein's state depends on the membrane voltage, which influences the gating of these channels. During depolarization, when the threshold voltage is reached, the channels open, allowing K+ ions to exit the cell, and they close again as the membrane repolarizes.
Step-by-step explanation:
The state that the K+ channel protein adopts is influenced by several factors, one of which includes the voltage across the membrane. Specifically, in the case of voltage-gated K+ channels, a change in membrane potential to a certain threshold (such as -50 mV) prompts the channel to open. This event is carefully timed, occurring just as the influx of Na+ ions peaks during the depolarization phase. Once the membrane potential repolarizes and passes -50 mV again, the gates of the K+ channel close with a slight delay, which leads to a brief continued outflux of K+, causing the hyperpolarizing overshoot.
The channel then returns to its closed state, and the resting potential is maintained by the ongoing activities of the non-gated channels and the Na+/K+ pump which operates via an anti-porter mechanism, using ATP to transport ions across the cell membrane.