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Glossary - N

Displaying glossary terms beginning with the letter N: 1 - 50 of 58 in total
nanograms per milliliter (ng/ml)
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).
narcolepsy
A sleep disorder that causes extreme sleepiness and uncontrollable sleep attacks, making a person fall asleep at inappropriate times during the day.
nasolabial folds
Lines in the skin leading from the nose to the outer corners of the mouth. Also known as smile or laugh lines.
natural killer (NK) cells
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.
natural recoverers
People who overcome addiction without treatment or formal self-help programs.
nebulizer
A device that converts a liquid medicine into a mist that can be breathed in.
necrosis
The premature death of living cells or tissues.
Related health topics: Flu (Influenza)
needle biopsy
Use of a hollow needle to remove a small sample of tissue for examination.
neoadjuvant therapy
A helper treatment given before a primary treatment is started, such as when chemotherapy is done before surgery in order to shrink a tumor.
Related health topics: Pancreatic Cancer
neonatal
Relating to an infant younger than 4 weeks of age.
neoplasm
An abnormal growth of tissue, either cancerous or benign.
nephritis
Inflammation of the kidneys.
nephropathy
Kidney disease.
nerve block
Injection of a medication into one or more nerves to relieve pain.
nerve growth factor
A molecule in the body that promotes the growth and repair of nerve cells.
nerve-sparing
When referring to prostatectomy, the surgical procedure that preserves the nerves needed to allow the penis to become erect.
neuralgia
A burning or stabbing pain that follows the path of a nerve.
neuritic plaques
Clumps of sticky proteins found in the brains of people with Alzheimer's disease.
neurofibrillary tangles
Twisted strands of proteins that are found inside the dead or dying nerve cells of people with Alzheimer's disease.
neuroleptic agents
Powerful tranquilizing drugs used to treat schizophrenia.
neurologist
A physician trained to diagnose and treat disorders of the nervous system, including the brain and spinal cord.
neuromuscular junction
The tiny space between the end of a nerve and the surface of a muscle.
neuron
A nerve cell.
neuropathy
Nerve damage and resulting loss of sensation, movement, or other function.
neuropeptides
Small proteins that aid in transmitting signals between nerve cells.
neurosyphilis
A rare infection of the brain or spinal cord that occurs when syphilis goes untreated for many years.
neurotransmitter
A chemical messenger that helps nerve signals bridge the gap between nerve cells.
neurotransmitter receptors
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.
neurotransmitters
Chemicals released by nerve cells that transmit messages to other nearby cells.
neutral alignment
Keeping the body in a straight line from head to toe except for the slight natural curves of the spine.
neutral posture
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.
neutral spine
A position in which the back is straight except for the slight natural curves of the spine.
neutropenia
An abnormally low number of white blood cells.
neutrophils
White blood cells that seek out and engulf foreign cells.
nitrates
Medications that widen blood vessels; usually used to treat chest pain from angina and other heart problems.
nitric oxide (NO)
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).
Related health topics: Esophageal Cancer, Stomach Cancer
nitroglycerin
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.
NMDA (N-methyl-D-aspartame) receptor
A molecule on the surface of a brain cell that admits calcium when activated by the chemical messenger glutamate.
nociceptors
Nerve endings that initiate the sensation of pain; they detect pain and transmit pain information to the brain and spinal cord.
nocturia
Waking up more than once during the night to urinate.
Related health topics: Pain
nodule
A small rounded bump or knot of tissue.
nomogram
A chart or graph of mathematical calculations of risk; used in making treatment recommendations and predicting outcomes.
Related health topics: Hyperthyroidism
non-HDL cholesterol
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.
non-insulin-dependent diabetes
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.
non-invasive test
A test that does not require any medical instruments to break the skin or enter the body.
non-REM sleep
The sleep phase that includes deep sleep, the type considered most important for preventing daytime sleepiness.
nonketotic hyperglycemic hyperosmolar syndrome
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.
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.
nonsteroidal anti-inflammatory drug (NSAID)
Drugs that reduce swelling and pain.
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.