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atrioventricular (AV) node
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A major part of the electrical system in the heart that acts as a gateway between the atria and the ventricles. An electrical signal generated by the sinoatrial node (the heart's natural pacemaker) moves through the heart until it reaches the atrioventricular node, a cluster of cells at the bottom of the right atrium. The AV node delays the signal before it is passed to the ventricles. This lets the atria fully contract before the ventricles contract.
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atrium
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One of the two upper chambers of the heart.
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atrium (plural, atria)
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One of the heart's two upper chambers. The right atrium receives deoxygenated blood from the body; the left atrium receives oxygenated blood from the lungs.
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atrophy
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Wasting away of an organ or
tissue due to undernourishment, disease, or aging.
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atypical lobular hyperplasia
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An overgrowth of abnormally shaped
cells in areas of the breast that produce milk (
lobules). atypical lobular hyperplasia is not cancerous but may become
cancer.
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audiogram
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A chart that shows a person's ability to hear at different pitches or frequencies.
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audiologist
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A health professional who assesses hearing and fits
hearing aids.
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audiometry
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A complete hearing test that involves listening to sounds of different frequencies and volume.
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auditory nerve
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A nerve in the
inner ear that transmits information about sound to the brain.
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aura
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Sensations such as chills, flashes of light, or a blind spot that come just before the occurrence of medical problems such as migraines or
seizures.
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autoantibodies
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autoimmune disease
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A disease in which the immune system mistakenly identifies healthy
tissues and organs as threats and responds by attacking and destroying them.
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autoimmune response
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When the body's immune system mistakenly views the body's own
tissues and organs as foreign invaders and attacks them.
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autologous fat transplant
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Removal of fat from one part of the body to use as filler in another part, for example, to fill wrinkles and lines in the face and lips.
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autonomic nervous system
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The part of the nervous system that controls involuntary actions, such as
blood pressure or breathing. It also plays an important role in the fight or flight response to danger.
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autonomic neuropathy
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Damage to the nerves that control involuntary body functions, such as digestion, heart rate, and bladder and
bowel function.
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autopsy
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Surgically opening and examining a body after death to see if any diseases are present and to determine the cause of death.
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avulsion
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The tearing away of one part of the body from another?for example, a
tendon tearing away from a bone.
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axillary
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The armpit.
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axis
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The second
vertebra of the neck (from the skull); also called the C-2 vertebra.
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axon
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The long, slender extension of a nerve cell that conducts electrical impulses away from the nerve's cell body and on to nearby nerves.
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axon terminal
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B cell
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White blood
cells that come from bone marrow, and produce antibodies to fight off disease.
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bacteria
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Tiny single-celled organisms. Some bacteria cause disease, although most are harmless.
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balance
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Ability to maintain equilibrium while stationary or moving.
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balloon angioplasty
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A procedure to open clogged heart
arteries. A surgeon inserts and inflates a tiny balloon. It widens the blocked
artery then expands a small wire mesh tube to keep the artery open.
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balloon dilation
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A surgical procedure to open a narrowed vessel or tube, such as the
urethra,
esophagus, or
artery. A small, deflated balloon is inserted into the area and inflated to widen it.
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bariatric surgery
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One of several types of weight loss surgery performed on people who are dangerously
overweight, to restrict or reduce food intake and/or absorption.
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barium study
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An imaging test that allows doctors to see the inside of the
esophagus and upper
stomach. It involves swallowing a barium solution, which coats the esophagus and makes it possible for x-rays to see the inside of the intestine.
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Barrett's esophagus
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basal cell carcinoma
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The most common skin cancer. Basal cell carcinoma doesn't spread to internal organs.
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basal ganglia
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Clusters of nerve
cells deep in the brain that play an important role in movement.
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baseline EKG
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basilar artery
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The
artery that supplies blood to the
cerebellum, the brainstem, and the back of the brain.
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benign
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Harmless; often used to refer to a
tumor that is not
cancerous and does not usually spread.
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benign orgasmic headache
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A severe headache that occurs when orgasm is reached.
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benign prostatic hyperplasia (BPH)
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A noncancerous enlargement of the
prostate gland that obstructs the flow of urine.
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benzodiazepines
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Anti-anxiety medications that work by helping to maintain levels of the
neurotransmitter GABA in the brain.
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bereavement
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The period of grief and mourning after a death.
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beriberi
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A nervous system or heart disorder caused by lack of the vitamin thiamine (B1).
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Bernstein test
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A test to try to reproduce
heartburn symptoms; used by doctors to diagnose GERD (gastroesophageal reflux disease).
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beta blockers
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beta carotene
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A richly colored compound (red, yellow, or orange) found in many plants, fruits, and vegetables that the body can convert into vitamin A.
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beta cells
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beta-agonists
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A medication that opens airways by relaxing the muscles around the airway; used to treat
asthma or COPD (chronic obstructive pulmonary disease).
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beta-amyloid
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An abnormal protein deposited in the brain in Alzheimer's disease.
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beta-blockers
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A class of drugs that slow the heartbeat, lessen the force of each contraction, and reduce the contraction of blood vessels in the heart, brain, and throughout the body by blocking the action of beta-adrenergic substances such as adrenaline (epinephrine) at the beta receptor. Beta blockers, also known as beta-adrenergic blocking agents, are used to treat many cardiovascular conditions, including abnormal heart rhythms, angina, and high blood pressure. They also improve survival after a heart attack.
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biguanides
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Medications that stop the
liver from making excess
glucose (sugar) and improve sensitivity to
insulin.
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bile
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A thick, yellow-green fluid produced by the liver that aids in digestion.
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bile acids
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Fatty substances made by the gallbladder that aid in digestion.
