The wave of depolarization begins in the right atrium, and the impulse spreads across the superior portions of both atria and then down through the contractile cells. The contractile cells then begin contraction from the superior to the inferior portions of the atria, efficiently pumping blood into the ventricles.
What happens to the heart during 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 is 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.
How does cardiac depolarization occur?
Depolarization occurs when the permeability to sodium (PNa+) increases, and sodium flows into the cell (Phase 0, Fig 3). … Fast action potential of cardiac contractile cell has four phases 0-4. the voltage gated sodium channels inactivate.
What is cardiac depolarization and repolarization?
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. 8.
What is the difference between depolarization and repolarization?
Depolarization is caused when positively charged sodium ions rush into a neuron with the opening of voltage-gated sodium channels. Repolarization is caused by the closing of sodium ion channels and the opening of potassium ion channels.
What does depolarization mean in ECG?
A wave of depolarization traveling toward a positive electrode results in a positive deflection in the ECG trace. A wave of depolarization traveling away from a positive electrode results in a negative deflection. A wave of repolarization traveling toward a positive electrode results in a negative deflection.
Does depolarization mean relaxation?
When the electrical signal of a depolarization reaches the contractile cells, they contract. When the repolarization signal reaches the myocardial cells, they relax. Thus, the electrical signals cause the mechanical pumping action of the heart.
Is depolarization contraction or relaxation?
Initially, both the atria and ventricles are relaxed (diastole). The P wave represents depolarization of the atria and is followed by atrial contraction (systole). Atrial systole extends until the QRS complex, at which point, the atria relax.
Which stage is indicative for depolarization?
Phase 0 is the phase of depolarization; Phase 1 through 3 is the phases during which repolarization occurs; Phase 4 is the resting phase with no spontaneous depolarization. During phase zero, the phase of rapid depolarization, voltage-gated Na+ channels open, resulting in a rapid influx of Na+ ions.
What are the two types of action potential in the heart?
Key Concept: There are two types of action potentials in the…
- Fast/long action potentials are produced in working cells and Purkinje fibers. Working cells do not exhibit automaticity, and they lack a spontaneous depolarization to threshold for producing an action potential. …
- Slow/brief action potentials are produced in the SA & AV nodes.