Question

Which of the following is the value for the action potential of a cell?

• A. 0.70 mV
• B. -20 mV
• C. +20 mV
• D. +50 mV

Hint:

During an action potential, the membrane potential briefly becomes positive — around +20 mV — due to rapid sodium influx.

Answer 1

The Correct Option is C

The action potential of a cell refers to a rapid rise and subsequent fall in voltage or membrane potential across a cellular membrane.
At rest, most cells (especially neurons and muscle cells) maintain a resting potential of about -70 mV.
During an action potential, the membrane depolarizes due to an influx of sodium ions ($\text{Na}^+$), causing the voltage to rise.
This depolarization continues until the membrane potential becomes positive — typically peaking around +20 mV.
This peak is considered the value of the action potential, beyond which repolarization and recovery follow.
Other values like -20 mV are closer to depolarization thresholds but not the peak action potential.