Question

The rapid depolarization phase of a contractile cell is also known as phase ________.

A) 0
B) 1
C) 2
D) 3
E) 4

Answer 1

The rapid depolarization phase of a contractile cell is known as phase 0, during which there is a surge of positively charged ions that increases membrane potential.

Step-by-step explanation:

The rapid depolarization phase of a contractile cell, which begins with the opening of voltage-gated sodium channels and results in a rapid influx of positively charged ions, is known as phase 0. This phase sees the membrane potential quickly rise to about +30 mV. Following this, the action potential enters a plateau phase characterized by the opening of slow Ca²+ channels, before eventually moving to the repolarization phase where K+ channels open, leading the cell back to its resting state.