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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 ...
The sinoatrial node (SA node) is the primary pacemaker of the heart. It is a region of cardiac muscle on the wall of the upper right atrium near to the superior vena cava entrance. The cells that make up the SA node are specialized cardiomyocytes known as pacemaker cells that can spontaneously generate cardiac action potentials.
The origin of the sinoatrial node artery is not related to coronary artery dominance, which means the side (right or left) that provides the circulation to the back of the heart. In contrast, the atrioventricular nodal branch, that is the artery that brings blood to the atrioventricular node, depends on coronary artery dominance. [citation needed]
An impulse (action potential) that originates from the SA node at a relative rate of 60–100 bpm is known as a normal sinus rhythm. If SA nodal impulses occur at a rate less than 60 bpm, the heart rhythm is known as sinus bradycardia. If SA nodal impulses occur at a rate exceeding 100 bpm, the consequent rapid heart rate is sinus tachycardia ...
Another form of voltage-gated potassium channels are the delayed rectifier potassium channels. These channels carry potassium currents which are responsible for the plateau phase of the action potential, and are named based on the speed at which they activate: slowly activating I Ks , rapidly activating I Kr and ultra-rapidly activating I Kur .
Normally, the sinoatrial node (SA node) produces an electrical signal to control the heart rate. The signal travels from the SA node to the ventricles through the atrioventricular node (AV node). In an AV block, this electrical signal is either delayed or completely blocked.
The AV node's normal intrinsic firing rate without stimulation (such as that from the SA node) is 40–60 times/minute. [13] This property is important because loss of the conduction system before the AV node should still result in pacing of the ventricles by the slower pacemaking ability of the AV node.
SA node: 60–100 bpm; Atrioventricular node(AVN): 40–60 bpm; Purkinje fibres: 20–40 bpm; The potentials will normally travel in order SA node → Atrioventricular node → Purkinje fibres Normally, all the foci will end up firing at the SA node rate, not their intrinsic rate in a phenomenon known as overdrive-suppression.