The electrical potential of the cell membrane becomes less negative or more positive due to Na+ or Ca2+ entering the cell. This is called what?

• A. Depolarization
• B. Hyperpolarization
• C. Repolarization
• D. Resting potential

Answer: (A)

When positive ions rush into a cell, the inside becomes less negative and tends toward zero, sometimes becoming positive. This shift toward a more positive membrane potential is called depolarization. It’s the change that brings the neuron or muscle cell closer to firing an action potential, because reaching a threshold triggers voltage-gated channels to open and propagate the signal.

Hyperpolarization would be the membrane potential becoming more negative than the resting level, typically due to continued K+ efflux or Cl- influx. Repolarization is the process of returning from depolarization back toward the resting potential after a spike. Resting potential is the steady, negative voltage when the cell is not signaling, maintained by ion pumps and leak channels.