white matter

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Human spinal cord

Understand the structure and functions of the central nervous system

white matter

anatomy

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July 15, 2026

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Human spinal cord — Human spinal cord Lower cervical segment of the human spinal cord. In this photograph of a cross section, the white matter is shown stained dark.

White matter is a component of the central nervous system, primarily found in the brain and spinal cord. It is characterized by its whitish color, which comes from the myelin sheath that insulates nerve fibers, known as axons. This myelin is composed of fatty materials, protein, and water, and it is formed by glial cells.12

The white matter lies beneath the gray matter in the brain and surrounds a butterfly-shaped area of gray matter in the spinal cord. The myelin sheath is crucial for the rapid transmission of nerve impulses, allowing them to jump between gaps in the sheath, a process called saltatory conduction. Diseases that damage this myelin, known as demyelinating diseases, can disrupt nerve function by blocking electrical impulses.324

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human nervous system
Cerebrum
…is an inner core of white matter, which is composed of myelinated commissural nerve fibers connecting the cerebral hemispheres via the corpus callosum, and association fibers connecting different regions of a single hemisphere. Myelinated fibers projecting to and from the cerebral cortex form a concentrated fan-shaped band, known as the…
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…is an inner core of white matter, which is composed of myelinated commissural nerve fibers connecting the cerebral hemispheres via the corpus callosum, and association fibers connecting different regions of a single hemisphere. Myelinated fibers projecting to and from the cerebral cortex form a concentrated fan-shaped band, known as the…
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cerebrum
…of myelinated nerve fibres, the white matter, and an outer cortex of gray matter. The cerebral cortex is responsible for integrating sensory impulses, directing motor activity, and controlling higher intellectual functions. The human cortex is several centimetres thick and has a surface area of about 2,000 square cm (310 square…
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…of myelinated nerve fibres, the white matter, and an outer cortex of gray matter. The cerebral cortex is responsible for integrating sensory impulses, directing motor activity, and controlling higher intellectual functions. The human cortex is several centimetres thick and has a surface area of about 2,000 square cm (310 square…
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human nervous system
The spinal cord
…myelinated nerve fibers (known as white matter) arranged around the periphery of a symmetrical butterfly-shaped cellular matrix of gray matter. The gray matter contains cell bodies, unmyelinated motor neuron fibers, and interneurons connecting either the two sides of the cord or the dorsal and ventral ganglia. Many interneurons have short…
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…myelinated nerve fibers (known as white matter) arranged around the periphery of a symmetrical butterfly-shaped cellular matrix of gray matter. The gray matter contains cell bodies, unmyelinated motor neuron fibers, and interneurons connecting either the two sides of the cord or the dorsal and ventral ganglia. Many interneurons have short…
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nervous system
The vertebrate system
…myelinated neurons dominate are called white matter. Efferent, or motor, nerve fibres carry impulses away from the central nervous system; afferent, or sensory, fibres carry impulses toward the central nervous system. Visceral fibres innervate the viscera such as the heart and intestines, and somatic fibres innervate the body-wall structures such…
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…myelinated neurons dominate are called white matter. Efferent, or motor, nerve fibres carry impulses away from the central nervous system; afferent, or sensory, fibres carry impulses toward the central nervous system. Visceral fibres innervate the viscera such as the heart and intestines, and somatic fibres innervate the body-wall structures such…
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