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Questions
Explain with the help of a suitable diagram conducting system of human heart.
With the help of a neat and labelled diagram, explain the conducting system of human heart.
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Solution
- Human heart is myogenic (myo-muscle, genic-originating from). The heart beat originates in modified cardiac muscles called Sinoatrial node (SA node) which lies in the wall of right atrium near the opening of superior vena cava.
- The SA node is called pace maker because it has the power to generate of wave of contraction.
- The wave of contraction of cardiac impulse generated by SA node is conducted by cardiac fibres to both the atria causing their contraction (atrial systole).
- The atrioventricular node (AV node) is located in the wall of right atrium near the opening of coronary sinus and receives the wave of contraction generated by the SA node through internodal pathway.
- The Bundle of His arises from AV nodes and divides into right and left bundle branches located in the interventricular septum.
- The bundle branches give rise to Purkinje fibres which penetrate into myocardium of ventricles. The bundle of His and Purkinje fibres conduct the wave of contraction from the AV node to the myocardium of ventricles causing their contraction (ventricular systole).
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Given below is a diagram of the external features of the human heart. Study the figure and answer the questions that follows:
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- Label the guidelines shown as 1 to 6 in the figure.
- Write the important role of parts 5 and 6.
- Name the chamber of the heart which collects blood from the lungs through a blood vessel. Also write the name of the blood vessel.
- Write one structural and one functional difference between the blood vessels 4 and 5.
- What happens when there is a blockage in any coronary artery or any of their branches?
