Medical Glossary Index:

N

Narcolepsy- a disorder that causes excessive sleepiness during the day and frequent and uncontrollable episodes of falling asleep

Narcosis- a drug (or other chemical)-induced drowsiness or stupor

Narcotic- an addictive substance that blunts the senses; can cause confusion, stupor, coma, and death with increased dosages

Narcotic analgesics- a type of painkiller that blocks the transmission of pain signals in the brain; often cause tolerance (the need for higher amounts of the drug to produce the same effect) and drug dependence

Nasal septum- the section of the nose that divides the left and right nostrils;
made of cartilage and bone and covered by a mucous membrane

Nasogastric tube- a thin, plastic tube that is inserted through the nose, down the esophagus, and into the stomach; used to drain, wash, or take samples from the stomach, or to feed very sick patients who cannot eat

Nasopharynx- the passageway connecting the back of the nose to the top of the throat

Natural childbirth- a technique of giving birth that stresses relaxation techniques so that the use of pain-relieving drugs can be minimized; also called prepared childbirth

Natural methods of family planning- methods of planning a family that focus
on a woman's time of ovulation, either so that pregnancy can be avoided or conception is likely

Nausea- feeling the need to vomit

Nebulizer- an instrument that provides a drug in its misted form through a face mask; used for severe asthma attacks and for children who have asthma but cannot use an inhaler

Necrosis- the medical term for the death of tissue cells

Needle aspiration- the use of a thin, hollow needle and syringe to remove body fluid for examination

Needle biopsy- the use of a hollow, wide-diameter needle to remove a sample
of tissue for examination

Neonate- a term used to describe a newborn infant from birth to 1 month of age

Neoplasm- another term for a tumor

Nephrectomy- the surgical removal of one or both kidneys

Nephritis- inflammation of one or both kidneys because of an infection, an abnormal immune system response, or a disorder of metabolism

Nephroblastoma- a fast-growing cancer of the kidneys that occurs most commonly in children under 4 years of age

Nephrolithotomy- surgical removal of a kidney stone

Nephrons- the tiny filtering units of the kidney

Nephrosclerosis- the replacement of normal kidney structures with scar tissue

Nephrostomy- the surgical placement of a tube into the kidney to drain urine

Nephrotic syndrome- symptoms that result from damage to the filtering units of the kidney

Nerve- a bundle of fibers that transmit electrical messages between the brain and areas of the body; these messages convey sensory or motor function information

Nerve block- the dulling of sensation in an area of the body by injecting a painkiller into or around a nerve leading to that section of the body

Nerve cell- the basic unit of the nervous system; transmits chemical messages throughout the body

Nerve compression- pressure on a nerve, which can cause nerve damage and muscle weakness

Neuralgia- pain along the course of a nerve caused by irritation or damage to the nerve

Neural tube- the tube located along the back of an embryo that later develops into the spinal cord and brain

Neural tube defects- problems in the development of the spinal cord and brain in an embryo, such as the failure of the spine to enclose the spinal cord (spina bifida) and the failure of the brain to develop (anencephaly)

Neuritis- inflammation of a nerve, often characterized by pain, numbness, or tingling; also used to describe nerve damage and disease from causes other than inflammation

Neuroblastoma- a cancerous childhood tumor located in the adrenal glands or the sympathetic nervous system

Neurofibrillary tangles- abnormal spiral filaments on nerve cells in the brain; characteristic of Alzheimer disease

Neurofibromatosis- a condition in which connective tissue tumors occur on nerves in the skin

Neuroleptic- an antipsychotic drug

Neuroma- a noncancerous tumor occurring in nerve tissue

Neuron- another term for a nerve cell

Neuropathy- disease, inflammation, or damage to the nerves connecting the brain and spinal cord to the rest of thebody

Neurosis- relatively mild emotional disorders (such as mild depression and phobias)

Neurotoxins- chemicals that attack and damage nerve cells

Neurotransmitters- chemicals that transfer messages from one nerve cell to another or from a nerve cell to a muscle cell

Neutrophil- a type of white blood cell

Nevus- a marking on the skin; can be present at birth (birthmark) or develop later (such as a mole)

Newborn respiratory distress syndrome- a disorder in which premature babies lack surfactant, a substance that stops the lungs from collapsing

Niacin- a vitamin important in many chemical processes in the body; also known as vitamin B3

Night terrors- a form of nightmlare causing abrupt awakening in terror; occurs mostly in children

Nitrates- a group of drugs that widen blood vessels; used to treat insufficient blood supply to the heart (angina pectoris) and reduced pumping efficiency of the heart (heart failure)

Nocturia- urination or a sleep-disturbing need to urinate during the night

Nocturnal emission- ejaculation of semen during sleep, which is normal in adolescent males; commonly called a wet dream

Node- a small, rounded tissue mass

Nodule- a small lump of tissue that is usually abnormal; can form under the skin
or protrude

Nondisjunction- an error that occurs during the division of sex chromosomes, causing either too much or too little genetic information to be placed in an egg or sperm when it is formed

Non-Hodgkin's lymphoma- any cancer in lymphoid tissue (found mostly in the spleen and lymph glands) that is not Hodgkin's disease

Non-insulin-dependent diabetes- a type of diabetes mellitus that occurs mainly in those over 40 who are overweight; it is usually treated with diet changes and drugs that increase production of insulin by the pancreas (also known as type II diabetes mellitus)

Noninvasive- a term that is used to describe medical procedures that do not
enter or penetrate the body; also refers to noncancerous tumors that do not spread
to other sections of the body

Nonnarcotic analgesic- a drug that relieves pain by blocking the production of chemicals that stimulate pain-sensing nerves

Nonsteroidal anti-inflammatory drugs- a group of drugs that relieve pain and reduce inflammation

Norepinephrine- a hormone that regulates blood pressure by causing blood vessels to narrow and the heart to beat faster when blood pressure drops

Norwalk virus- a virus that causes acute gastroenteritis

Nosocomial infection- an infection acquired in a hospital

NSAID- see Nonsteroidal anti-inflammatory drug

Nucleic acids- substances found in every living organism that provide the instructions for development; includes DNA and RNA

Nucleotide bases- molecules that form nucleic acids

Nucleus- the center or most important point of an object

Numbness- the lack of sensation in a part of the body because of interruption of nerve impulses

Nurse-midwife- a registered nurse who specializes in the care of a mother and child during pregnancy, labor, and delivery

Nutrient- any substance that the body can use to maintain its health

Nystagmus- persistent, rapid, involuntary movement of the eyes