white substance

substance /sub·stance/ (sub´stans)

1. matter with a particular set of characteristics.

2. material constituting an organ or body.

3. psychoactive s.

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black substance  substantia nigra.

controlled substance  any drug regulated under the Controlled Substances Act.

gelatinous substance  substantia gelatinosa.

gray substance  substantia grisea.

ground substance  the gel-like material in which connective tissue cells and fibers are embedded.

H substance  H antigen (2).

medullary substance 

1. substantia alba.

2. the soft marrowlike substance of the interior of an organ.

substance P  an 11–amino acid peptide, present in nerve cells throughout the body and in special endocrine cells of the intestine. It increases contraction of gastrointestinal smooth muscle, causes vasodilatation, and is a sensory neurotransmitter.

perforated substance 

1. anterior perforated s., an area anterolateral to each optic tract, pierced by branches of the anterior and middle cerebral arteries.

2. posterior perforated s., an area between the cerebral peduncles, pierced by branches of the posterior cerebral arteries.

psychoactive substance  any chemical compound that affects the mind or mental processes; used particularly for drugs used therapeutically in psychiatry, the major classes being the antipsychotic, antidepressant, anxiolytic-sedative, and mood-stabilizing drugs.

reticular substance 

1. see under formation.

2. the netlike mass seen in red blood cells after vital staining.

Rolando's gelatinous substance  substantia gelatinosa.

slow-reacting substance of anaphylaxis  (SRS-A) an inflammatory agent released by mast cells in the anaphylactic reaction, inducing a slow, prolonged contraction of certain smooth muscles and acting as an important mediator of allergic bronchial asthma.

transmitter substance  neurotransmitter.

white substance  substantia alba.

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white substance

n.

See white matter.

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white substance.

See white matter.

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white matter, white substance

the white nervous tissue, constituting the conducting portion of the brain and spinal cord, composed mostly of myelinated nerve fibers. Gray matter or substance is the term used to describe the tissues composed of unmyelinated fibers.