Hyperpolarization is caused by which ions -

Ans. is ' a' i.e., K+ o During depolarization (spike potential) there is opening of Na+ channels causing Na~ influx. This causes membrane potential to become +35 to +40 mV (from -70 mV of resting potential),o During repolarization phase channels open and there is K+ efflux. The membrane voltage falls back (repolarizes) to resting potential, i.e., -70 mV. At this voltage. K+ channels close, but quite slowly. Therefore, more K+ ions leak out, causing a brief period in which the voltage falls below' -70 mV, i.e. hyperplorization.o Then, K+/Na~ pump works to re-establish resting potential by pumping N+ ions back out and K+.' ions back into the cells.