CVS Practice Test

Are the cells in the SA node considered contractile?

1. Yes, they are highly contractile

2. No, they are minimally contractile

3. Yes, they are moderately contractile

4. No, they are non-contractile

The correct answer is: No, they are minimally contractile

The cells in the SA node, or sinoatrial node, are primarily responsible for generating electrical impulses that initiate the heartbeat. These cells are specialized pacemaker cells, which means their main function is to regulate the rhythm of the heart rather than to contract like typical cardiac muscle cells. While they do have some capacity for contraction, it is minimal compared to other cardiac muscle cells. This is why the answer indicating they are minimally contractile is appropriate. The SA node cells do not contain the same contractile proteins in significant amounts as found in the cardiac myocytes, which are responsible for the actual contraction of the heart muscle. Their primary role is to generate and conduct electrical signals to the rest of the heart, ensuring proper timing and coordination of heartbeat without the need for robust contraction. Thus, the correct answer reflects their functional characteristics accurately.