Question

Adding a chemical that reduces Na+ transport near the sinoatrial (SA) node would have what effect on the heart's intrinsic conducting system?

- The SA node would depolarize more quickly, increasing
the heart rate.
- The SA node would depolarize more quickly, decreasing
the heart rate.
- The SA node would depolarize less quickly, increasing the
heart rate.
- The SA node would depolarize less quickly, reducing the
heart rate.
- There will be no change.

Answer 1

The introduction of a chemical that reduces sodium transport near the SA node would result in the SA node depolarizing less quickly, subsequently reducing the heart rate.

Step-by-step explanation:

Adding a chemical that reduces Na+ transport near the sinoatrial (SA) node would slow down the rate of depolarization in the SA node, which would lead to a slower heart rate. This is because the movement of sodium ions into the cells during the prepotential phase helps to reach the threshold for depolarization faster. If sodium ion transport is reduced, it will take longer to reach the threshold, thereby slowing down the heart rate. This is reflected by the fact that parasympathetic stimulation typically slows heart rate by affecting potassium ion channels, but the principle is similar in that a slower rate of depolarization generally reduces heart rate.

Therefore, the correct answer to the question is that the SA node would depolarize less quickly, reducing the heart rate.