Bio help please?

Question

Atherosclerosis usually occurs in the small arteries that supply blood to the muscles of the heart. What are probable physiological effects if the blockage partially affects the function of the: (a) SA node and the (b) AV node? What part of the cardiac cycle will be interrupted in each case?

Answer 1

The SA (sinoatrial) node is considered the "pacemaker" of the heart. Depolarization of the SA node spreads first to the atrium, causing them to contract. If there is a defect in the function of the SA node that prevents the spread of the action potential, another cell would have to take over the role as the "pacemaker" (they are called ectopic pacemakers).

The action potential from the SA node first reaches the atrium, then the AV node. The AV node is also considered a delay center for the action potential. The delay is necessary to regulate the contractions between the atria and ventricles to ensure that they do not contract at the same time.