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1. physical material having form and weight under ordinary conditions; called also substance.
gray matter areas of the nervous system where the nerve fibers are unmyelinated (not enveloped by a myelin sheath); it contains the bodies of the nerve cells. Tissue composed of myelinated fibers is called white matter. The cerebral cortex is entirely composed of gray matter and the cerebellum also contains some deep-seated masses of it. The spinal cord has a central core of gray matter surrounded by white matter; in cross section, its gray matter is shaped approximately like the letter H. Called also substantia grisea and gray substance.
those regions of the brain and spinal cord that are made up primarily of the cell bodies and dendrites of nerve cells rather than myelinated axons.
1. Brownish-gray nerve tissue, especially of the brain and spinal cord, composed of nerve cell bodies and their dendrites and some supportive tissue.
2. Informal Brains; intellect.
the gray nervous tissue found in the cortex of the cerebrum and cerebellum and the core of the spinal cord. It is predominantly composed of neuron cell bodies and unmyelinated axons. The gray color is produced by cytoplasmic elements seen in all cell bodies and processes not covered by whitish myelin. Nuclei in the gray substance of the spinal cord function as centers for all spinal reflexes. Also called gray substance. Compare white matter. See also cerebellum, cerebral cortex, cerebrum, spinal cord, spinal nerves.
gray mat·ter(grā mat'ĕr) [TA]
gray areas of brain and spinal cord made up primarily of cell bodies and dendrites of nerve cells rather than myelinated axons. White matter or substance is the tissue composed primarily of myelinated, or medullated, fibers.
The bodies of the nerve cells are centered in the gray matter. In the brain the gray matter may be external to white matter, e.g. cerebellum, or central to it, e.g. cerebrum. The cerebral cortex is composed of gray matter and there are some deep-seated nuclei too. In the spinal cord there is a central core of gray matter surrounded by white matter. On a cross-section of the spinal cord the gray matter follows the general pattern of the letter H.