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The pacesetter in the heart is called (a) AV node
(b) SA node
(c) Purkinje fibers
(d) Papillary muscles

Last updated date: 13th Jun 2024
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Hint: The cardiac impulse is triggered in one of the main components of the cardiac conduction mechanism, the mechanism that regulates the heart rate. It consists of a cluster of cells located in the upper part of the right atrium wall (the upper right chamber of the heart).

Complete Step by Step Answer: The SA node is the heart's natural pacemaker. The SA node (SA stands for sinoatrial) is one of the major components of the cardiac conduction system, the system that controls the heart rate. This developed system generates and conducts electrical impulses in the heart muscle, stimulating the heart to contract and pump blood.
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So, the answer is, “SA node.”

Additional Information: The electrical signal produced by the SA node travels down through the heart from cell to cell until it reaches the atrioventricular node (AV node), a cluster of cells situated in the middle of the organ heart between the atria and ventricles.
The autonomic nervous system can easily send a message to the SA node so that within only 3 to 5 seconds, it can in turn raise the heart rate to twice normal. During exercise, this fast response is necessary when the heart needs to increase its beating speed to keep up with the increased demand for oxygen from the body. Note: - Until the signal is allowed to pass down to the ventricles, the AV node functions as a gate that delays the electrical current. This pause means that before the ventricles are stimulated, the atria have a chance to completely contract. The electric current passes to the ventricles through special fibers inserted in the walls of the lower part of the heart after passing through the AV node. - To activate the start of the cardiac cycle, the autonomic nervous system, the same portion of the nervous system that regulates blood pressure, regulates the firing of the SA node.