What is the mechanism of action for calcium channel blockers?

Calcium channel blockers function by interrupting the influx of calcium ions into cells, particularly within vascular smooth muscle and cardiac muscle tissues. This mechanism leads to several physiological effects, such as vasodilation, reduced heart rate, and decreased myocardial contractility.

When calcium channel blockers are administered, they bind to voltage-gated calcium channels in the cell membranes. By blocking these channels, the entry of calcium ions is inhibited, which is crucial for muscle contraction in both the vascular system and the heart. As a result, the smooth muscle of blood vessels relaxes, leading to lowered blood pressure. In the heart, the reduced calcium influx decreases the force of contraction and slows down conduction through the AV node, which is beneficial in managing conditions like hypertension and arrhythmias.

The other options do not accurately describe the action of calcium channel blockers. They do not enhance calcium entry, promote calcium release from bone, or increase heart contractility; in fact, they do the opposite by inhibiting calcium's contribution to muscle contraction and excitability. This understanding is vital for effectively leveraging calcium channel blockers in clinical practice.