How they work Beta blockers have an antagonist action, meaning that they work by reducing the activity of the sympathetic nervous system therefore reducing the subsequent symptoms. They are beta adrenoceptor blocking agents, meaning that they block receptor sites for the hormones adrenaline and noradrenaline. When adrenaline binds a target receptor it stimulates the associated muscle, thus causing, for example, the heart muscles to increase beating. Therefore the usual physical reaction to stress is dampened. Breathing and heart rate do not increase and the person feels a lot calmer and less anxious. Beta blockers do not completely stop anxiety but mask the outward signs of it. Therefore they are particularly useful in acute stress situations such as giving a public speech. Someone giving a speech will no longer experience the outward signs of anxiety such as shaking, changes to the pitch of their voice or sweat on their forehead. Thus the negative effects of stress are reduced.