Question

10a. Describe the electrical activity of the cells of the SA node and explain how the SA node functions as the normal pacemaker.

10b. Using a single diagram, illustrate a myocardial action potential and the time course for myocardial contraction. Explain how the relationship between these two events prevents the heart from sustaining a contraction and how it normally prevents abnormal rhythms of electrical activity

Answer 1

10a. It is the integrated activity of these so-called pacemakers (P) cells that form the SA node. The sinus node continuously generates electrical impulses, thereby setting the normal rhythm and rate in a healthy heart. Hence, the SA node is referred to as the natural pacemaker of the heart.

# Its function is the main function of the SA node is to act as the normal pacemaker of the heart. ... Unlike atrial and ventricular cells, pacemaker cells in the sinus node do not have a resting phase. Instead, these cells have pacemaker potential, in which they begin to depolarize automatically after an action potential ends.