What is the normal depolarization point for most cells?

What is the normal depolarization point for most cells?

• A. +30 mV
• B. -70 mV
• C. -90 mV
• D. 0 mV

Answer: (A)

Depolarization, in this context, means the peak of the action potential—the moment when the cell’s membrane potential becomes least negative before it returns toward resting values. At rest, neurons and many other cells sit around −70 mV. When a sufficient stimulus arrives, voltage-gated Na+ channels open, causing a rapid influx of sodium that drives the membrane potential upward into the positive range. In most cells, this peak—where depolarization is greatest—reaches about +30 mV. After this peak, Na+ channels inactivate and K+ channels open, leading to repolarization and then a brief hyperpolarization before returning to rest. So, the normal depolarization point is around +30 mV, with some cells drifting a bit higher or lower depending on exact channel dynamics. The other values reflect resting, hyperpolarized, or near-neutral states, not the peak depolarization.

Depolarization, in this context, means the peak of the action potential—the moment when the cell’s membrane potential becomes least negative before it returns toward resting values. At rest, neurons and many other cells sit around −70 mV. When a sufficient stimulus arrives, voltage-gated Na+ channels open, causing a rapid influx of sodium that drives the membrane potential upward into the positive range. In most cells, this peak—where depolarization is greatest—reaches about +30 mV. After this peak, Na+ channels inactivate and K+ channels open, leading to repolarization and then a brief hyperpolarization before returning to rest. So, the normal depolarization point is around +30 mV, with some cells drifting a bit higher or lower depending on exact channel dynamics. The other values reflect resting, hyperpolarized, or near-neutral states, not the peak depolarization.