spinal cord


spinal cord
the cord of nerve tissue extending through the spinal canal of the spinal column.
[1830-40]

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In vertebrates, the body's major nerve tract.

In humans it is about 18 in. (45 cm) long, running from the base of the brain through the vertebral column. It is covered by the meninges and cushioned by cerebrospinal fluid. It connects the peripheral nervous system (outside the brain and spinal cord) to the brain. The spinal cord and the brain constitute the central nervous system. Sensory impulses reach the brain via the spinal cord, and impulses from the brain travel down the spinal cord to motor neurons, which reach the body's muscles and glands via the peripheral nerves. The peripheral nerves are connected to the spinal cord via the spinal nerves. In humans there are 31 pairs of spinal nerves containing both sensory and motor fibres, which originate in the spinal cord and pass out between the vertebrae. These nerves branch and relay motor impulses to all parts of the body. Injury to the spinal cord may result in loss of communication between the brain and outlying parts and cause paralysis, loss of sensation, or weakness in the parts of the body served by areas below the injured region. Because nerve cells and fibres are unable to regenerate themselves, the effects are usually permanent.

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      major nerve tract of vertebrates, extending from the base of the brain through the canal of the spinal column. It is composed of fibres that mediate reflex actions and that transmit impulses to and from the brain.

      Like the brain, the spinal cord is covered by three connective-tissue envelopes called the meninges. The space between the outer and middle envelopes is filled with cerebrospinal fluid, a clear, colourless fluid that cushions the spinal cord.

 A cross section of the spinal cord reveals white matter arranged around a butterfly-shaped area of gray matter. The white matter consists of myelinated fibres, or axons (axon), that form nerve tracts ascending to and descending from the brain. The white matter is grouped into discrete sectors called funiculi. The gray matter contains cell bodies, unmyelinated motor-neuron fibres, and interneurons connecting the two sides of the cord. Gray-matter cells form projections called horns. Fibres exiting the spinal cord from the dorsal and ventral horns join in paired tracts to form the spinal nerves (spinal nerve). Information travels up the ascending tracts of neurons and is sorted by the brain. Responses are induced by nerve impulses traveling down the descending tracts that stimulate motor neurons or that initiate glandular secretion. (See also nervous system, human.)
 

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Universalium. 2010.

Look at other dictionaries:

  • Spinal cord — Latin medulla spinalis The spinal cord nested in the vertebral column …   Wikipedia

  • Spinal cord — Spinal Spi nal, a. [L. spinalis, fr. spina the spine: cf. F. spinal. See {Spine}.] 1. (Anat.) Of, pertaining to, or in the region of, the backbone, or vertebral column; rachidian; vertebral. [1913 Webster] 2. Of or pertaining to a spine or spines …   The Collaborative International Dictionary of English

  • spinal cord — spinal cords N COUNT Your spinal cord is a thick cord of nerves inside your spine which connects your brain to nerves in all parts of your body …   English dictionary

  • spinal cord — n. the thick cord of nerve tissue of the central nervous system, extending down the spinal canal from the medulla oblongata …   English World dictionary

  • spinal cord — n the thick string of nerves enclosed in your ↑spine, by which messages are sent to and from your brain …   Dictionary of contemporary English

  • spinal cord — noun count the inner part of your SPINE that contains nerves going from your brain to the other parts of your body …   Usage of the words and phrases in modern English

  • spinal cord — ► NOUN ▪ the cylindrical bundle of nerve fibres which is enclosed in the spine and connected to the brain, with which it forms the central nervous system …   English terms dictionary

  • Spinal cord — The major column of nerve tissue that is connected to the brain, lies within the vertebral canal, and from which the spinal nerves emerge. The spinal cord and the brain constitute the central nervous system (CNS). The spinal cord consists of… …   Medical dictionary

  • spinal cord — noun a major part of the central nervous system which conducts sensory and motor nerve impulses to and from the brain; a long tubelike structure extending from the base of the brain through the vertebral canal to the upper lumbar region • Syn:… …   Useful english dictionary

  • spinal cord — UK / US noun [countable] Word forms spinal cord : singular spinal cord plural spinal cords medical the inner part of your spine that contains nerves going from your brain to the other parts of your body …   English dictionary


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