Question

Important Implications/traits of Cardiac AP. Which of the following characteristics is a key implication of the cardiac action potential?

A) Rapid depolarization phase
B) Prolonged plateau phase
C) Absence of refractory periods
D) Constant membrane potential

Answer 1

The prolonged plateau phase, due to the influx of calcium ions, is a key characteristic of the cardiac action potential, ensuring the cardiac muscle fully contracts before the next electrical event.

Step-by-step explanation:

A key implication of the cardiac action potential (Cardiac AP) is the prolonged plateau phase. This phase is due to the influx of calcium ions into cardiac contractile cells, which contributes to the extended refractory period of the cardiac muscle. This prolonged phase ensures that muscle cells have time to fully contract before another action potential can occur, preventing tetany and allowing the heart to pump blood effectively. It contrasts with skeletal muscle action potentials which lack this prolonged phase.

The cardiac action potential involves a rapid depolarization phase as well, where a swift influx of positively charged ions raises the membrane potential. However, it is the plateau phase, sustained by the slow opening of calcium channels, which is distinctive and crucial for the heart's function. After the plateau, repolarization occurs and the cell can prepare for the next action potential.