Evolve Pharmacology Practice Test

In pharmacology, an antagonist functions by blocking or inhibiting the action of a neurotransmitter or hormone. This means that when an antagonist binds to a receptor, it prevents the natural ligand (such as a neurotransmitter) from attaching and activating that receptor. As a result, the physiological response that would normally occur from the activation of that receptor is inhibited, effectively decreasing or nullifying its effects on the body.

This characteristic of antagonists is crucial in many therapeutic applications, where it can be used to modify physiological processes, manage symptoms, or counteract conditions where there is excessive activity of certain neurotransmitters or hormones. For example, in conditions like hypertension, beta-blockers act as antagonists by inhibiting the action of adrenaline on beta-adrenergic receptors, leading to lowered heart rate and blood pressure.

The other options pertain to different pharmacological actions. Enhancing the action of a neurotransmitter or hormone refers to the role of agonists, while competing with enzymes for substrate relates to enzyme inhibitors, and increasing drug metabolism typically involves enzyme inducers, not antagonists.