beta-blocker definition of beta-blocker in the Free Online Encyclopedia.

beta-blocker or beta-adrenergic blocking agent (bā`tə ăd'rənûr`jĭk), drug that reduces the symptoms connected with hypertension hypertension or high blood pressure, elevated blood pressure resulting from an increase in the amount of blood pumped by the heart or from increased resistance to the flow of blood through the small arterial blood vessels (arterioles).
..... Click the link for more information. , cardiac arrhythmias arrhythmia (ārĭth`mēə), disturbance in the rate or rhythm of the heartbeat.
..... Click the link for more information. , angina pectoris angina pectoris (ănjī`nə pĕk`tərĭs)
..... Click the link for more information. , migraine migraine (mī`grān), headache characterized by recurrent attacks of severe pain, usually on one side of the head.
..... Click the link for more information. headaches, and other disorders related to the sympathetic nervous system nervous system, network of specialized tissue that controls actions and reactions of the body and its adjustment to the environment. Virtually all members of the animal kingdom have at least a rudimentary nervous system.
..... Click the link for more information. . Beta-blockers also are sometimes given after heart attacks to stabilize the heartbeat. Within the sympathetic nervous system, beta-adrenergic receptors are located mainly in the heart, lungs, kidneys, and blood vessels. Beta-blockers compete with the nerve-stimulating hormone epinephrine epinephrine (ĕp'ənĕf`rīn), hormone important to the body's metabolism, also known as adrenaline.
..... Click the link for more information. for these receptor sites and thus interfere with the action of epinephrine, lowering blood pressure and heart rate, stopping arrhythmias, and preventing migraine headaches. Because it is also epinephrine that prepares the body for "fight or flight" in stressful or fearful situations, beta-blockers are sometimes used as antianxiety drugs antianxiety drug, drug administered for the relief of anxiety . Although their action is not fully understood, most antianxiety medications appear to affect the action of neurotransmitters in the brain (see serotonin and norepinephrine ).
..... Click the link for more information. , especially for stage fright and the like. People taking a beta-blocker must avoid caffeine, alcohol, and salty foods, because the interaction of those substances and the drug can raise the heart rate and blood pressure. Propranolol (Inderal) is a commonly used beta-blocker.

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beta-blocker