What is the group of cell that make the heart contract?

Answer 1

There are two nodes that can act as pacemakers for the heart and initiate contraction. In a normal healthy heart, the SA (sinoatrial) node acts as the pacemaker by depolarizing spontaneously ~60-80 times per minute. If damaged, the AV (atrio-ventricular) node can take over this function but does not depolarize as quickly, so the resting heart rate would be lower (40-50 times per minute).

Answer 2

There are are three types of muscles in the human body. The skeletal muscle which can be controlled voluntarily, the smooth muscles in the blood vessel walls and alimentary tract that cannot be controlled voluntarily but is controlled by the autonomic nervous system and the cardiac muscle that cannot be controlled voluntarily but is capable of generating electrical impulses on its own.

The repeated electrical impulses that makes the heart beat starts its journey at the Sino-Atrial Node, composed of nodal tissue which is altered cardiac muscle tissue capable of spontaneously generating electrical impulses, situated in the right atrial wall. (The heart has four chambers, a pair of atria and a pair of ventricles.) The electrical impulse generated gets conducted across the atrial wall to reach the Atrio-ventricular node in the inter-ventricular septum that separates the two sides of the heart. From the AV node conduction of the electrical impulse occurs across a system of the main bundle which branches off into left and right bundle branches and further branches carry the impulse across the whole ventricle. At a given time the atria and ventricles are in different phases of contraction and relaxation. It is the patterned flow of this electrical electrical impulse that makes the cardiac muscle contract in such a sequence that at the time that the atria contracts the ventricles are relaxed to receive blood from the atria and when the ventricle gets filled, it starts to contract and the valve between the atria and ventricle closes to prevent return and the blood gets pumped to the pulmonary circulation from the right ventricle and to the systemic general circulation from the left ventricle, while at this time, the atria is in a relaxed stage and receiving venous blood (The left and right side of the heart are normally sealed from one another).

This process of the cardiac cycle gets repeated 72 times per minute.

Answer 3

the sinoatrial node

Answer 4

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