How do calcium channel blockers primarily affect the heart and blood vessels?

Calcium channel blockers primarily function by slowing the movement of calcium into cells, which has a significant impact on both the heart and blood vessels. When calcium enters the cardiac and vascular smooth muscle cells, it leads to muscle contraction. By inhibiting this calcium influx, calcium channel blockers cause relaxation and dilation of blood vessels, effectively lowering vascular resistance. This dilating effect reduces the workload on the heart and can lead to decreased blood pressure.

In the heart, the reduction in calcium levels leads to a decrease in the strength of contractions (negative inotropic effect) and can also slow down the heart rate (negative chronotropic effect) by affecting the conduction system, specifically the sinoatrial (SA) and atrioventricular (AV) nodes. However, the primary mechanism of action remains the dilation of arteries and lowering of blood pressure rather than an increase in heart rate or electrical conduction. Thus, this chosen answer accurately reflects the main physiological effects of calcium channel blockers on the cardiovascular system.