What is the primary action of calcium channel blockers?

Calcium channel blockers primarily function by inhibiting the entry of calcium into vascular smooth muscle and cardiac muscle. Calcium is essential for various cellular processes, including muscle contraction. When calcium channels are blocked, it leads to relaxation of smooth muscle, particularly in the blood vessels, resulting in vasodilation. This decreases peripheral vascular resistance and lowers blood pressure.

In cardiac muscle, reduced calcium entry diminishes the force of contraction (negative inotropic effect) and can also slow down heart rate by affecting the electrical conduction through the heart (negative chronotropic effect). Therefore, the primary mechanism of action is pivotal in managing conditions such as hypertension, angina, and certain cardiac arrhythmias.

The other options do not accurately describe the primary action of calcium channel blockers. The practice of increasing heart rate and blood pressure contradicts their intended therapeutic effects. Stimulating adrenaline release and dilating airways are functions associated with different classes of medications, such as adrenergic agonists or bronchodilators, rather than calcium channel blockers.