Glossary of Terms & Definitions
Listed Alphabetically - "N"

Nebulization: Administration of medication to selected portions of the respiratory tract by droplets suspended in air.

Necrosis: Cell death due to infection or injury.

Negative feedback: The principle governing most control systems; a mechanism of response in which a stimulus initiates actions that reverse or reduce the stimulus.

Neonatal: Pertaining to the first four weeks after birth.

Neoplasm: A new growth that may be benign or malignant.

Nerve:  A cordlike bundle of nerve fibers (axons and/or dendrites) and its associated connective tissue coursing together outside the central nervous system.

Neural Tube Defect (NTD): A birth defect caused by abnormal development of the neural tube, the structure which gives rise to the central nervous system. Neural tube defects include anencephaly and spina bifida.

Neurologic: (or neurological): Involving nerves or the nervous system (brain, spinal cord, and all sensory and motor nerves).

Neuropathy: Malfunction or disease pathology of nerves.  Peripheral neuropathy refers to a disease or degenerative state of peripheral nerves resulting in pain, numbness, and sometimes muscle weakness.

Neurotoxic: Toxic or damaging to nervous tissue (brain and peripheral nerves). 

Neurotransmitter: A chemical that is released from a nerve cell, which transmits an impulse from that nerve cell to another nerve cell, or to another organ (a muscle, for example). Neurotransmitters are chemical messengers that transmit neurological information from one cell to another.

Neutrophils: Also called polymorphonuclear leukocytes because they are white blood cells with a multi-lobed nucleus. Neutrophils combat infection by internalizing and destroying disease causing organisms such as bacteria.

NIH: The National Institutes of Health are U.S. health agencies, devoted to medical research. Administered under the Department of Health and Human Services (HHS), the NIH consists of more than 20 separate Institutes and Centers.

Nucleic acids: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid). Long thread-like molecules made up of large numbers of nucleotides. Nucleotides are composed of a nitrogen containing base, a 5-carbon sugar, and one or more phosphate groups. The sequence of bases in DNA or RNA represents the genetic (hereditary) information of a living cell.

Nucleotides: Molecules composed of a nitrogen containing base, a 5-carbon sugar, and one or more phosphate groups. Long strands of nucleotides form nucleic acids (see above). The sequence of bases in DNA or RNA represents the genetic (hereditary) information of a living cell.

Nucleus: A membrane-bound cellular organelle, which contains DNA organized into chromosomes.