Topics :Sainoatrial node Name: Bidhan sarkar

 Sinoatrial node The sinoatrial node (SA node), also known as sinus node, is a group of cells located in the wall of the right atrium of the heart.cellsright atriumheart The SA node (SA stands for sinoatrial) is one of the major elements in the cardiac conduction system, the system that controls the heart rate.

 Where it is located ? The SA node is located in The wall (myocardium) of the myocardium right atriumright atrium, laterally to the entrance of the superior vena cavasuperior vena cava in a region called the sinus venarum.sinus venarum

 The structure of SA NODE The sinoatrial node is a banana-shaped structure that varies in size, usually between millimeters (mm) long, 5–7 mm wide, and 1–2 mm deep.

The SA node is the heart's natural pacemaker.pacemaker The electrical impulses are generated there. The SA node is also called the sinus node. The sinoatrial node was first discovered by a young medical student, Martin Flack, in the heart of a mole.Martin Flackmole

 How it works ? The main role of a sinoatrial node cell is to initiate action potentials, so that it can pass throughout the heart and cause contraction. An action potential is a change in voltage (membrane potential) across the membrane of the cell, produced by the movement of charged atoms (ions)membraneions

Normal cardiac conduction is initiated by the dominant pacemaker of the heart; the SA node

The electrical signal generated by the SA node moves from cell to cell down through the heart until it reaches the atrioventricular node (AV node). The atrioventricular node (AV node), a cluster of cells situated in the center of the heart between the atria and ventricles.

The AV node serves as a gate that slows the electrical current before the signal is permitted to pass down through to the ventricles After passing the AV node, the electrical current travels to the ventricles along special fibers embedded in the walls of the lower part of the heart.

Other cells within the heart (including the purkinje fibers and atrioventricular node )can also initiate action potentials; however, they do so at a slower rate and therefore, if the SA node is working, it usually beats the AVN to it.

 The heart rate The heart rate is the number of times the heart beats in the space of a minute. Heart rate depends on the rate at which the sinoatrial node produces action potentials. Heart rateaction potentials hereAt rest, heart rate is between 60 and 100 beats per minute here

The heart rate during exercise should be roughly equal to 220 bpm minus the age of the person.roughly equal to 220 bpm

This quick response is important during exercise when the heart has to increase its beating speed to keep up with the body's increased demand for oxygen.

 WHY SA NODE LEADS THE HEART?

 Clinical significance : Sinus node dysfunction describes an irregular heartbeat caused by faulty electrical signals of the heart. When the heart's sinoatrial node is defective, the heart’s rhythms become abnormal – typically too slow or exhibiting pauses in its function or a combination, and very rarely faster than normal.  Sinus node dysfunction

 Ischaemia Blockage of the arterial blood supply to the SA node can therefore cause ischaemia and cell death in the SA node.ischaemia This can disrupt the electrical pacemaker function of the SA node, and can result in sick sinus syndrome.sick sinus syndrome