Hint: Some special types of muscle cells are present in the heart that are capable of generating regular impulses without any activation from the outside of the heart.
Complete answer: In the heart, entire pumping (of blood) activity is done by the contraction of muscles. These contractions in the human heart are activated by a specialized altered muscle of the heart known as the sinoatrial node (SA node) which is positioned in the right atrium. The SA node has the inherent capability to generate a wave of contraction and also controls the heartbeat. This is the reason it is termed as the pacemaker of the heart. As the heartbeat is triggered by the sinoatrial node, and the impulse of contraction originates in the heart, the human heart is thus known as myogenic. In humans, the Heart is situated inside the thoracic cavity and is protected by the chest bone. The human heart consists of four chambers namely left and right atrium and also left and right ventricle. In the heart oxygenated blood flows from Lungs to the left atrium and from there it flows into the left ventricle. From the left ventricle, oxygenated blood is pumped into the various parts of the body. The deoxygenated blood from the whole body is collected into the right atrium, from where it flows into the right ventricle and finally pumps towards the lungs for oxygenation. As the heartbeat is triggered by the sinoatrial node, and the impulse of contraction originates in the heart, the human heart is thus known as myogenic.
Note: -Similar types of myogenic hearts are also found in Molluscs and some other vertebrates. -The volume of blood pumped by the heart can vary from five to 30 liters per minute. -About 2,000 gallons of blood is pumped by the human heart every day. -People who have blood type AB have the highest risk of heart disease.
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