What is depolarization and repolarization in heart?

Depolarization with corresponding contraction of myocardial muscle moves as a wave through the heart. 7. Repolarization is the return of the ions to their previous resting state, which corresponds with relaxation of the myocardial muscle.

What are the 5 phases of cardiac action potential?

Membrane currents that generate the a normal action potential. Resting (4), upstroke (0), early repolarization (1), plateau (2), and final repolarization are the 5 phases of the action potential.

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 depolarization of heart?

What is meant by depolarization of the heart? Depolarization of the heart is the orderly passage of electrical current sequentially through the heart muscle, changing it, cell by cell, from the resting polarized state to the depolarized state until the entire heart is depolarized.

What is heart repolarization?

Ventricular repolarization is a complex electrical phenomenon which represents a crucial stage in electrical cardiac activity. It is expressed on the surface electrocardiogram by the interval between the start of the QRS complex and the end of the T wave or U wave (QT).

Where does repolarization occur in the heart?

This repolarization process occurs in the muscle of the ventricles about 0.25 second after depolarization. There are, therefore, both depolarization and repolarization waves represented in the electrocardiogram.

How many phases are in cardiac action potential?

five phases
The cardiac action potential has five phases as shown in Fig. 2. During phase 0, membrane permeability to potassium decreases and fast sodium channels open, producing rapid depolarization from −90 mV to +10 mV. During phase 1, there is partial repolarization, because of a decrease in sodium permeability.

What are the phases of action potential?

The action potential has three main stages: depolarization, repolarization, and hyperpolarization.

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.

What is heart muscle depolarization?

Depolarization of the heart leads to the contraction of the heart muscles and therefore an EKG is an indirect indicator of heart muscle contraction. The cells of the heart will depolarize without an outside stimulus. This property of cardiac muscle tissue is called automaticity, or autorhythmicity.

What causes depolarization in the heart?

Because of slow inward current of sodium and a voltage gated increase in calcium conductance (via T channels) Phase 0—depolarization. As opposed to the ventricular muscle action potential, this occurs because of voltage gated calcium channels opening.

What happens at repolarization?

Repolarization is a stage of an action potential in which the cell experiences a decrease of voltage due to the efflux of potassium (K+) ions along its electrochemical gradient. This phase occurs after the cell reaches its highest voltage from depolarization.

What happens to the cardiac action potential after depolarization?

If depolarization reaches threshold, the contractile cells, in turn, generate action potentials, firstdepolarizing then repolarizing. After depolarization, the cardiac myofibrils in contractile cellsslide over each other resulting in muscle contraction. After repolarization these cells relax.

How does depolarization and repolarization work in the cell?

Depolarization and repolarization. The Sodium-potassium pump in the cell membranes of cells continuously pumps 3 sodium ions to the extracellular space for every 2 potassium ions pumped into the intracellular space resulting in a net deficit of positive ions intracellularly Proteins and phosphate ions, which are negatively charged substances,…

How does repolarization in Autorhythmic cells work?

Page 10. Repolarization in Autorhythmic Cells This reversal of membrane potential triggers the opening of potassium channels, resulting i npotassium rapidly leaving the cell. Potassium efflux produces repolarization, bringing the membrane potential back down to its restinglevel.

What happens when a cell is excited or depolarized?

Once a cell is excited (depolarized), it can excite adjacent cells and “pass on” its action potential, spreading depolarization to more and more cells. Content on this page requires a newer version of Adobe Flash Player.