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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.
- Sinoatrial Node
- Atrioventricular Node
- Atrioventricular Bundle
- Purkinje Fibres
The sinoatrial (SA) nodeis a collection of specialised cells (pacemaker cells), and is located in the upper wall of the right atrium, at the junction where the superior vena cava enters. These pacemaker cells can spontaneously generateelectrical impulses. The wave of excitation created by the SA node spreads via gap junctions across both atria, res...
After the electrical impulses spread across the atria, they converge at the atrioventricular node– located within the atrioventricular septum, near the opening of the coronary sinus. The AV node acts to delay the impulses by approximately 120ms, to ensure the atria have enough time to fully eject blood into the ventricles before ventricular systole...
The atrioventricular bundle(bundle of His) is a continuation of the specialised tissue of the AV node, and serves to transmit the electrical impulse from the AV node to the Purkinje fibres of the ventricles. It descends down the membranous part of the interventricular septum, before dividing into two main bundles: 1. Right bundle branch– conducts t...
ThePurkinje fibres(sub-endocardial plexus of conduction cells) are a network of specialised cells. They are abundant with glycogen and have extensive gap junctions. These cells are located in thesubendocardial surfaceof the ventricular walls, and are able to rapidly transmit cardiac action potentials from the atrioventricular bundle to the myocardi...
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Jul 22, 2023 · The sinoatrial (SA) node, often referred to as the natural pacemaker of the heart, plays a crucial role in initiating and regulating the electrical impulses that control the heart's rhythm.
Aug 31, 2022 · The sinoatrial (SA) node is the natural pacemaker of the heart. It generates electrical impulses that cause the heart’s chambers to contract, setting the heart rate. The SA node typically...
The impulses originate in the heart's natural pacemaker (the sinus or sinoatrial node—a small mass of tissue in the wall of the right atrium), which generates a tiny electrical current.
Sympathetic nervous system control and heart function: Stimulation by the sympathetic nervous system results in the following effects on the heart (Table 1): Positive chronotropic effect (increase in heart rate): The sinoatrial (SA) node is the predominate pacemaker of the heart. It is located within the upper posterior wall of the right atrium ...
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Aug 17, 2023 · Although all parts have the ability to generate action potentials and thus heart contractions, the sinuatrial (SA) node is the primary impulse initiator and regulator in a healthy heart. This aspect makes the SA node the physiological pacemaker of the heart.
