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The sinoatrial node (also known as the sinuatrial node, SA node or sinus node) is an oval shaped region of special cardiac muscle in the upper back wall of the right atrium made up of cells known as pacemaker cells. The sinus node is approximately 15 mm long, 3 mm wide, and 1 mm thick, located directly below and to the side of the superior vena ...
Therefore, the resting membrane potential is mostly equal to K + equilibrium potential and can be calculated using the Goldman-Hodgkin-Katz voltage equation. However, pacemaker cells are never at rest. In these cells, phase 4 is also known as the pacemaker potential. During this phase, the membrane potential slowly becomes more positive, until ...
In the pacemaking cells of the heart (e.g., the sinoatrial node), the pacemaker potential (also called the pacemaker current) is the slow, positive increase in voltage across the cell's membrane, that occurs between the end of one action potential and the beginning of the next.
The cells that make up the SA node are specialized cardiomyocytes known as pacemaker cells that can spontaneously generate cardiac action potentials. These signals are propagated through the heart's electrical conduction system. [1] [2] Only one percent of the heart muscle cells are conductive, the rest of the cardiomyocytes are contractile.
The funny current is highly expressed in spontaneously active cardiac regions, such as the sinoatrial node (SAN, the natural pacemaker region), the atrioventricular node (AVN) and the Purkinje fibres of conduction tissue. The funny current is a mixed sodium–potassium current that activates upon hyperpolarization at voltages in the diastolic ...
The duration of this slow diastolic depolarization (pacemaker phase) thus governs the cardiac chronotropism. It is also important to point out that the modulation of the cardiac rate by the autonomic nervous system also acts on this phase. Sympathetic stimuli induce the acceleration of rate by increasing the slope of the pacemaker phase, while ...
Cardiac physiology or heart function is the study of healthy, unimpaired function of the heart: involving blood flow; myocardium structure; the electrical conduction system of the heart; the cardiac cycle and cardiac output and how these interact and depend on one another.
If there is a blockage between the AV node and the SA node, the atria may not contract at all. [6] [7] Junctional rhythm can be diagnosed by looking at an ECG: it usually presents without a P wave or with an inverted P wave. Retrograde, or inverted, P waves refers to the depolarization from the AV node back towards the SA node. [8]