Glossary

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N

Nasoduodenal tube: 

A nasoduodenal tube is a flexible rubber tube that is inserted through the nose and into the duodenum (the section of the small intestine closest to the stomach) via the esophagus and stomach. It can be used to remove the contents of or decompress the small intestine or to provide nutrition support or medication.

The NIH is one of the world’s foremost medical research centers and the federal focal point for medical research in the United States. The NIH, comprising 27 separate Institutes and Centers, is one of eight health agencies of the Public Health Service that, in turn, is part of the U.S. Department of Health and Human Services.

National Institutes of Health (NIH): 

Necrosis:

Cell death. Loss of cells, tissues, or parts of a structure or organ due to the progressively degrading actions of certain enzymes, such as the degradation of DNA within the nucleus of dying cells. Necrosis may result from a loss of blood supply (ischemia), infection, excessive exposure to ionizing radiation, certain chemicals, or extreme temperatures.

Neoplastic:

Relating to the formation of a neoplasm (tumor) or a new, abnormal growth characterized by uncontrolled, progressive multiplication of cells. Neoplasms may be benign or malignant.

Nerve conduction velocity (NCV) test:

A diagnostic study during which both sensory and motor nerves are repeatedly stimulated in order to measure the speed at which nerve impulses are conducted. Unusually slow conduction velocities suggest damage to nerve fibers (e.g., loss of the protective covering surrounding certain nerve fibers [demyelination] or other disease process).

Nervous system: 

The nervous system of the human body is divided into two interconnected systems: the central nervous system, which is made up of the brain and spinal cord, and the peripheral nervous system. The peripheral nervous system is further divided into the somatic nervous system (made up of peripheral nerve fibers that send sensory information to the central nervous system and motor nerve fibers that project to skeletal muscle) and the autonomic nervous system.

Neuroacanthocytosis:

Also known as choreoacanthocytosis, this is a genetic disorder that most often becomes apparent between the ages of 25 to 45 years. The disorder is usually transmitted as an autosomal recessive trait. Associated symptoms may include generalized chorea; dystonia affecting muscles of the mouth and tongue; potentially mutilating lip- and tongue-biting; and sudden, involuntary, repetitive muscle movements (motor tics) and vocalizations (vocal tics). Patients may also develop personality changes and cognitive decline, seizures, parkinsonism, atrophy of muscle tissue (amyotrophy), and difficulties speaking and swallowing. Neuroimaging studies may reveal atrophy of certain regions of the basal ganglia (e.g., caudate nuclei and putamen [striatum]). The disorder may be confirmed by blood tests revealing the presence of abnormal circulating red blood cells that have spur-like or thorny projections (acanthocytosis).

Neurochemical:

Referring to the chemistry or biochemical processes of the nervous system, such as activities involving naturally produced chemicals (i.e., neurotransmitters) that enable nerve cells (neurons) to communicate.

Neurodegenerative:

Marked by or pertaining to neurologic degeneration; deterioration of the structure or function of tissue within the nervous system.

Neuroimaging: 

The production of detail, contrast, and clearness in images of the brain and spinal cord (central nervous system) through the use of computed tomography (CT) scanning, magnetic resonance imaging (MRI), positron emission tomography (PET) scanning, or other imaging techniques to assist in diagnosis, treatment decisions, or research.

Neuroleptic:

a drug used to treat psychotic behavior.

Neuroleptic malignant syndrome:

a life-threatening neurologic disorder most often caused by an adverse reaction to neuroleptic or antipsychotic drugs. Symptoms include high fever, sweating, unstable blood pressure, stupor, muscular rigidity, and autonomic dysfunction. In most cases, the disorder develops within the first 2 weeks of treatment with the drug; however, the disorder may develop any time during the therapy period. The syndrome can also occur in people taking anti-parkinsonism drugs known as dopaminergic if those drugs are discontinued abruptly.

Neuron: 

An individual nerve cell.

Neuronal:

Pertaining to a neuron or neurons.

Neuroprotective effect: 

Having the ability to prevent or slow the death of neurons. The drug selegiline (Eldepryl®) may have a neuroprotective effect, possibly by preventing formation of free radicals.

Neuroreceptor:

Specific sites on the surface of a nerve cell to which certain special substances (neurotransmitters) bind, initiating the conduction of impulses (or signals) to other nerve cells.

Neurotoxin:

a substance that interferes with the electrical activity or functioning of nerve cells (neurons), preventing them from communicating with each other.

Neurotransmitter: 

A specialized substance (such as norepinephrine or acetylcholine) that transfers nerve impulses across spaces between nerve cells (synapses). Neurotransmitters are naturally produced chemicals by which nerve cells communicate.

Nigrostriatal system:

Referring to the substantia nigra, the striatum, and the connection between them.

Nocardia asteroides:

Nocardia asteroides are gram-positive bacteria that are found throughout the world in the soil. Localized infections usually occur in the skin following contamination of a scrape or scratch, and disseminated infections typically occur when a person with a compromised immune system inhales the bacteria. The primary site of disseminated infection is typically the lungs, where abscesses form, but the infection may spread to other parts of the body, including the brain, liver, and kidneys.

Nomenclature:

System of names used in a particular scientific discipline to consistently and methodically designate certain classifications and avoid confusion or ambiguity.

Non-ergotoline medication:

Referring to long nerve fibers (axons) that have myelin sheaths. Consisting of segmented, multilayered wrappings of myelin, a whitish protein, myelin sheaths wrap around certain nerve fibers, providing electrical insulation and serving to speed the transmission of nerve signals.

Non-kinesigenic:

Not induced by movement; provoked by factors other than sudden motions. This term often refers to abrupt episodes of involuntary movement that occur spontaneously or may be worsened by fatigue, stress, alcohol or caffeine intake, heat or cold, fasting, or other factors.

Noradrenaline (norepinephrine): 

 A vasoconstrictor whose release triggers action within the sympathetic nervous system, the part of the nervous system that regulates certain involuntary responses during times of stress. Noradrenaline serves as a neurotransmitter that stimulates receptors (alpha- and beta-adrenergic receptors) at effector organs supplied or innervated by certain sympathetic nerve fibers (postganglionic adrenergic fibers). In addition to its production by neurons, noradrenaline is also secreted by the inner region of the adrenal glands (adrenal medulla). The release of noradrenaline serves to deepen breathing, raise blood pressure, and increase the heart rate. It also plays a role in regulating mood.

NREM sleep:

Non-REM (nonrapid eye movement) sleep, which is the normal period of dreamless, lighter sleep as compared to the deeper REM sleep. NREM sleep accounts for the major portion of sleep.

Nuclear envelope:

The nuclear envelope is a membrane that surrounds the nucleus in eukaryotic cells, separating the DNA in the nucleus from the rest of the cell.

Nucleus:

The nucleus is the part of the cell that contains the genetic material; it is surrounded by the nuclear envelope.

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