What is the mechanism through which calcium channel blockers function?

Calcium channel blockers function primarily by blocking calcium from entering cells, particularly in the vascular smooth muscle and cardiac muscle. This action leads to arterial dilation, reducing vascular resistance, which effectively lowers blood pressure. By inhibiting calcium entry during the action potential, these drugs reduce the force of contraction in the heart and decrease the overall workload of the heart. This mechanism is crucial for their therapeutic effects in conditions like hypertension and angina.

The other options describe different mechanisms that do not pertain to the action of calcium channel blockers. For instance, inhibiting the conversion of angiotensinogen refers to the action of ACE inhibitors, while stimulating alpha receptors is related to the action of alpha-adrenergic agonists. Promoting sodium retention is associated with certain hormone effects, such as those of aldosterone, and does not describe the primary action of calcium channel blockers.