What is an expected effect of calcium channel blockers on the heart's activity?

Calcium channel blockers primarily function by inhibiting the influx of calcium ions through voltage-gated calcium channels in cardiac and smooth muscle cells. This mechanism has several important effects on the heart's activity. A key expected effect is the slowing of impulse formation in the sinoatrial (SA) node and atrioventricular (AV) node, which leads to a decrease in heart rate (a negative chronotropic effect).

By reducing the number of calcium ions available for muscle contraction and electrical conduction, these drugs help in managing conditions such as hypertension and certain arrhythmias. This slowing down of impulse formation is crucial, as it allows the heart to maintain a more controlled rhythm and decreases the overall workload on the heart, aiding in the management of various cardiovascular issues.

The other options, such as increased contractility, increased venous return, and arterial contraction, do not accurately reflect the effects of calcium channel blockers, as these medications generally reduce cardiac contractility and promote vasodilation rather than increasing blood return or causing contraction of arterial walls.