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nanograms per milliliter (ng/ml)
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A small quantity of a substance; equivalent to one-billionth of a gram (454 grams make 1 pound) in one-thousandth of a liter (1 liter is approximately 1 quart).
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narcolepsy
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A sleep disorder that causes extreme sleepiness and uncontrollable sleep attacks, making a person fall asleep at inappropriate times during the day.
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nasolabial folds
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Lines in the skin leading from the nose to the outer corners of the mouth. Also known as smile or laugh lines.
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natural killer (NK) cells
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A type of white blood
cell of the immune system. These cells destroy other cells that fail to display the right chemical flags signaling that they are normal cells.
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natural recoverers
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People who overcome
addiction without treatment or formal self-help programs.
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nebulizer
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A device that converts a liquid medicine into a mist that can be breathed in.
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necrosis
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needle biopsy
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Use of a hollow needle to remove a small sample of
tissue for examination.
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neoadjuvant therapy
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A helper treatment given before a primary treatment is started, such as when
chemotherapy is done before surgery in order to shrink a
tumor.
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neonatal
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Relating to an infant younger than 4 weeks of age.
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neoplasm
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nephritis
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nephropathy
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Kidney disease.
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nerve block
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Injection of a medication into one or more nerves to relieve pain.
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nerve growth factor
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A molecule in the body that promotes the growth and repair of nerve
cells.
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nerve-sparing
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When referring to prostatectomy, the surgical procedure that preserves the nerves needed to allow the penis to become erect.
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neuralgia
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A burning or stabbing pain that follows the path of a nerve.
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neuritic plaques
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neurofibrillary tangles
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neuroleptic agents
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Powerful tranquilizing drugs used to treat schizophrenia.
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neurologist
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A physician trained to diagnose and treat disorders of the nervous system, including the brain and spinal cord.
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neuromuscular junction
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The tiny space between the end of a nerve and the surface of a muscle.
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neuron
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neuropathy
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Nerve damage and resulting loss of sensation, movement, or other function.
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neuropeptides
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Small
proteins that aid in transmitting signals between nerve
cells.
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neurosyphilis
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A rare
infection of the brain or spinal cord that occurs when syphilis goes untreated for many years.
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neurotransmitter
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A chemical messenger that helps nerve signals bridge the gap between nerve
cells.
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neurotransmitter receptors
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Cell structures (usually proteins) that recognize specific neurotransmitters and bind to them. Once bound, a receptor often changes shape, causing a cascade of chemical events within the cell. These events can alter which genes are turned on or off and can make the cell more or less likely to release its neurotransmitters.
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neurotransmitters
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Chemicals released by nerve cells that transmit messages to other nearby cells.
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neutral alignment
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Keeping the body in a straight line from head to toe except for the slight natural curves of the spine.
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neutral posture
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A standing or seated position in which the chin is parallel to the floor; the shoulders, hips, and knees are at even heights; and the knees and feet point straight ahead.
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neutral spine
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A position in which the back is straight except for the slight natural curves of the spine.
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neutropenia
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An abnormally low number of white blood
cells.
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neutrophils
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White blood
cells that seek out and engulf foreign cells.
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nitrates
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Medications that widen
blood vessels; usually used to treat chest pain from angina and other heart problems.
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nitric oxide (NO)
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A compound produced by the endothelium (the lining of the interior walls of
arteries) that helps widen
blood vessels and counteract
high blood pressure. Also called endothelium-derived relaxing factor (EDRF).
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nitroglycerin
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A drug that relaxes blood vessels and increases the supply of blood and oxygen to the heart while reducing its workload. It is commonly used to treat angina.
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NMDA (N-methyl-D-aspartame) receptor
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A molecule on the surface of a brain
cell that admits
calcium when activated by the chemical messenger
glutamate.
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nociceptors
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Nerve endings that initiate the sensation of pain; they detect pain and transmit pain information to the brain and spinal cord.
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nocturia
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Waking up more than once during the night to urinate.
Related health topics:
Pain
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nodule
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A small rounded bump or knot of
tissue.
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nomogram
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A chart or graph of mathematical calculations of risk; used in making treatment recommendations and predicting outcomes.
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non-HDL cholesterol
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The sum of all cholesterol types other than high-density lipoprotein (HDL). These include very-low-density lipoprotein, low-density lipoprotein, and intermediate-density lipoprotein.
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non-insulin-dependent diabetes
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Now called type 2 diabetes. A disease in which levels of blood sugar (glucose) are too high because the body doesn't produce enough insulin (a substance that helps the body use or store glucose from food) or because
cells can't use insulin properly.
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non-invasive test
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A test that does not require any medical instruments to break the skin or enter the body.
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non-REM sleep
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The sleep phase that includes
deep sleep, the type considered most important for preventing daytime sleepiness.
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nonketotic hyperglycemic hyperosmolar syndrome
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A rare and very serious condition associated with
type 2 diabetes. Symptoms include extremely high (more than 800 mg/dl) blood sugar levels, severe dehydration, and changes in mental status, ultimately resulting in
coma.
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nonproliferative retinopathy
-
A condition in which the walls of the small
blood vessels in the
retina leak serum and tiny pockets of swelling form in the walls of blood vessels. Also called background retinopathy.
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nonsteroidal anti-inflammatory drug (NSAID)
-
Drugs that reduce swelling and pain.
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noradrenaline
-
A
hormone produced by adrenal
glands that puts the body on heightened alert when a threat is perceived (the fight-or-flight response). Also known as norepinephrine.
