Any of a group of drugs that bind preferentially to beta adrenoceptors and hence block their stimulation by the body’s own neurotransmitters, adrenaline and noradrenaline. Beta blockers, such as propranolol, oxprenolol, and atenolol, are used to treat disorders of the cardiovascular system, including high blood pressure (hypertension), angina pectoris, and irregularities of heartbeat (arrhythmias). They are also effective in treating anxiety and glaucoma (as eye drops) and in preventing migraine. They tend to dampen the effects of exercise or stress on heart rate, heart output, and blood pressure, as well as improving the oxygenation of the heart muscles. The release of the enzyme renin from the kidneys is also reduced, leading to an overall fall in arterial blood pressure.