An isolated cell of human heart automatically generates excitement impulses with frequency of 60 times per minute. This cell was taken from the following heart structure:

Answer options

1. Atrium
2. Ventricle
3. Atrioventricular node
4. Sinoatrial node
5. His’ bundle

Explanation

The SA node is the heart's natural pacemaker consisting of a cluster of cells that are situated in the upper part of the wall of the right atrium The electrical impulses are generated there with a rate of 60-80/min. During stress, the sympathetic nervous system produces the dominant effects in the body. The atrioventricular node is 40-60/min and less in the HIS bundle.