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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sub·stance (sbstns)

n.

1. That which has mass and occupies space; matter.

2. A material of a particular kind or constitution.

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substance

the material constituting an organ or body.

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black substance

substantia nigra.

controlled substance

see controlled substances act.

depressor substance

a substance that tends to decrease activity or blood pressure.

gray substance

nerve tissue composed of predominantly nerve cell bodies, unmyelinated nerve fibers, and supporting tissue. See also gray matter.

ground substance

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

medullary substance

1. the white matter of the central nervous system, consisting of axons and their myelin sheaths.

2. the soft, marrow-like substance of the interior of such structures as bone, kidney and adrenal gland.

substance P

an undecapeptide present in the intestine, where it induces contraction of the intestine and dilatation of blood vessels; it is also present in a number of neuronal pathways in the brain and in primary sensory fibers of peripheral nerves, and may be a neurotransmitter associated with transmission of pain impulses.

perforated substance

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

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

pressor substance

a substance that raises blood pressure.

reticular substance

the netlike mass of threads seen in erythrocytes after vital staining.

slow-reacting substance

see slow-reacting substance.

threshold s's

those substances (e.g. glucose) excreted into the urine only when their concentration in plasma exceeds a certain value.

white substance

tissue consisting mostly of myelinated nerve fibers and constituting the conducting portion of the brain and spinal cord; see also white matter.