What effect do beta-blockers have on adrenaline?

Beta-blockers are a class of medications that primarily function by blocking the action of adrenaline (also known as epinephrine) at beta-adrenergic receptors in the body. When adrenaline is released, it prepares the body for a 'fight or flight' response by increasing heart rate, dilating airways, and promoting blood flow to muscles. By blocking these receptors, beta-blockers inhibit these effects, leading to a decrease in heart rate and blood pressure, among other cardiovascular effects.

This mechanism is particularly useful in treating conditions like hypertension, anxiety, and certain heart conditions, where reducing the effects of adrenaline can lead to improved health outcomes. Therefore, the correct understanding of beta-blockers is that they directly block the effects of adrenaline, making the selected answer accurate in this context.