What are the 3 phases of cardiac muscle contraction?

Phase 0—depolarization because of the opening of fast sodium channels. Potassium flux also decreases. Phase 1—partial repolarization because of a rapid decrease in sodium ion passage as fast sodium channels close. Phase 2—plateau phase in which the movement of calcium ions out of the cell, maintains depolarization.

What are the 4 phases of cardiac action potential?

Action potential in cardiomyocytes

Phase 4: The resting phase.
Phase 0: Depolarization.
Phase 1: Early repolarization.
Phase 2: The plateau phase.
Phase 3: Repolarization.

What happens in Phase 4 of action potential?

Phase 4 is the spontaneous depolarization (pacemaker potential) that triggers the action potential once the membrane potential reaches threshold between -40 and -30 mV). As ions flow through open channels, they generate electrical currents that change the membrane potential.

Why is there a plateau phase in cardiac muscle?

This plateau phase allows for a longer muscle contraction and gives time for the nearby cardiac muscle cells to depolarize. This is important in allowing the heart to contract in a steady, uniform and forceful manner.

What is the rest cycle of the heart called?

The period of relaxation is called diastole. The period of contraction is called systole. Diastole is the longer of the two phases so that the heart can rest between contractions. heart is known as the cardiac cycle.

Which is the correct sequence of events of the cardiac cycle?

Diastole, atrial systole, ventricular diastole, ventricular systole.

What drug will prolong phase 3 of the cardiac action potential?

Ivabradine is considered to act specifically on the sinoatrial node by inhibiting the If current (the funny current) to slow automaticity. However, in vitro studies show that ivabradine prolongs phase 3 repolarization in ventricular tissue.

Why is refractory period of cardiac muscle long?

The refractory period is very long to prevent the possibility of tetany, a condition in which muscle remains involuntarily contracted. In the heart, tetany is not compatible with life, since it would prevent the heart from pumping blood.

What is the plateau stage?

Plateau follows the excitement or sexual arousal phase, and is characterised by increased heart and respiratory rates, increased sexual pleasure, increased muscle tension, and is followed by orgasm. …