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Narcolepsy
A sudden, uncontrollable disposition to sleep occurring at irregular intervals, with or without obvious predisposing or exciting cause.
National Cancer Institute
The US government agency for cancer research and information.
Natural Killer Cell (NK)
A lymphocyte which, unlike other lymphocytes, does not require specific activation by foreign antigen. They are considered to play a 'front line' role in controlling infection, curbing infection until a specific, coordinated immune response can be mounted.
Near point of accommodation
The closest point in front of the eyes that an object may be clearly focused.
Near point of convergence
The maximum extent the two eyes can be turned inward.
Needle aspiration (OF THE BREAST)
Uses a thin needle and syringe to collect tissue or drain a lump after using a local anesthetic.
Needle biopsy
Biopsy procedure in which a small sample of tissue is removed through a hollow needle.
Neoadjuvant therapy
Chemotherapy given before surgery or radiation therapy.
Nephrectomy
Surgical removal of the kidney.
Nephropathy
Diabetic kidney disease.
Nerve conduction test
Procedure to determine nerve impulse generation.
Nerve sparing technique
A surgical technique often used during a radial prostatectomy in which one or both of the neurovascular bundles controlling erections are spared.
Neural mobilization
Techniques by which neural tissues are moved, either by movement relative to their surroundings or by tension development.
Neural plasticity
Ability of the brain and/or certain parts of the nervous system to change in order to adapt to new conditions, such as an injury.
Neural prostheses
Devices that substitute for an injured or diseased part of the nervous system to enhance the function.
Neural stimulation
To activate or energize a nerve through an external source.
Neural tube defect
Type of birth defect, such as spina bifida, that results from failure of the spinal cord or brain to develop normally in a fetus.
Neuralgia
A painful condition caused by disorders of the nervous system.
Neurasthenia
Nervous exhaustion. A functional neurosis marked by intense nervous irritability and weakness.
Neuritis
Inflammation of a nerve or nerves.
Neurogenic
Of nerve origin.
Neurogenic communication disorder
Inability to exchange information with others because of hearing, speech, and/or language problems caused by impairment of the nervous system.
Neuromyasthenia
Muscular weakness, usually of emotional origin.
Neuron
A cell specialized to conduct and generate electrical impulses and to carry information from one part of the brain to another.
Neuropathology
The study of the nervous system.
Neuropsychiatric
Relating to organic and functional diseases of the nervous system.
Neurotransmitters
Substances produced in neurons that promote or inhibit the conduction of nerve impulses, such as epinephrine, norepinephrine, dopamine, serotonin, and gamma-aminobutyrate.
Neurotransmitters
Chemical substances that carry impulses from one nerve cell to another; found in the space (synapse) that separates the transmitting neuron's terminal (axon) from the receiving neuron's terminal (dendrite).
Newborn screening
Examining blood samples from a newborn infant to detect disease-related abnormalities or deficiencies in gene products. There are other purposes for , and methods of, screening newborns.
NIH
National Institutes of Health.
Nissen fundoplication
Operation to sew the top of the stomach (fundus) around the esophagus; used to stop stomach contents from flowing back into the esophagus (reflux) and to repair a hiatal hernia.
Nitrogenous base
A nitrogen containing molecule having the chemical properties of a base.
Noise-induced hearing loss
Hearing loss that is caused either by a one-time or repeated exposure to very loud sound(s).
Non-insulin-dependent diabetes
See type 2 diabetes.
Noninvasive procedures
A diagnostic effort or treatment that does not require entering the body or puncturing the skin.
Nonsense mutation
A mutation in which a codon is changed to a stop codon, resulting in a truncated protein product.
Non-steroidal anti-inflammatory drugs (NSAIDS)
Medications that produces antipyretic, analgesic, and anti-inflammatory effects.
Nonsyndromic hereditary hearing impairment
Hearing loss or deafness that is inherited and is not associated with other inherited clinical characteristics.
Nontropical sprue
See celiac disease.
Nonulcer dyspepsia
Constant pain or discomfort in the upper gastrointestinal tract.
Norepinephrine
A neurotransmitter found mainly in areas of the brain that are involved in governing autonomic nervous system activity, especially blood pressure and heart rate.
Norwalk virus
Virus that may cause gastrointestinal (GI) infection and diarrhea. (See also gastroenteritis.)
Nuclear medicine
A specialized area of radiology that uses very small amounts of radioactive substances to examine organ function and structure.
Nucleic acid
A large molecule composed of nucleotide subunits.
Nucleotide
A subunit of DNA or RNA, consisting of one chemical base plus a phosphate molecule and a sugar molecule.
Nucleus
The cell structure that houses the chromosomes.
Nutrients
Proteins, carbohydrates, fats, vitamins, and minerals provided by food and necessary for growth and the maintenance of life.
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