How do beta-blockers affect heart function?

Beta-blockers primarily function by blocking the effects of adrenaline (epinephrine) and norepinephrine on beta-adrenergic receptors in the heart and vascular system. This action leads to a decrease in heart rate and myocardial contractility, ultimately reducing the heart's workload. By inhibiting these receptors, beta-blockers help to lower blood pressure and heart rate, which is particularly beneficial in conditions such as hypertension, heart failure, and certain arrhythmias.

Their ability to reduce the stimulation of the heart by sympathetic nerves helps to prevent excessive cardiac stress and decreases the oxygen demand of the myocardium. This makes beta-blockers an essential class of medication in the management of various cardiovascular diseases.

The other options do not accurately describe the primary mechanism of action of beta-blockers. While some beta-blockers may have secondary effects that promote vasodilation, this is not their main mechanism. Similarly, they do not increase heart rate or cardiac output, nor do they directly enhance glucose utilization in cardiac tissues.