spinal cord, the part of the nervous system nervous system, network of specialized tissue that controls actions and reactions of the body and its adjustment to the environment. Virtually all members of the animal kingdom have at least a rudimentary nervous system.
..... Click the link for more information. occupying the hollow interior (vertebral canal) of the series of vertebrae that form the spinal column spinal column, bony column forming the main structural support of the skeleton of humans and other vertebrates, also known as the vertebral column or backbone. It consists of segments known as vertebrae linked by intervertebral disks and held together by ligaments.
..... Click the link for more information. , technically known as the vertebral column. Extending from the first lumbar vertebra to the medulla at the base of the brain brain, the supervisory center of the nervous system in all vertebrates. It also serves as the site of emotions, memory, self-awareness, and thought.
..... Click the link for more information. , the spinal cord of a human adult is about 18 in. (45 cm) long. Structurally, the cord is a double-layered tube, roughly cylindrical in cross section. The outer layer consists of white matter, i.e., myelin-sheathed nerve fibers. These are bundled into specialized tracts that conduct impulses triggered by pressure, pain, heat, and other sensory stimuli or conduct motor impulses activating muscles and glands. The inner layer, or gray matter, is primarily composed of nerve cell bodies. Within the gray matter, running the length of the cord and extending into the brain, lies the central canal through which circulates the cerebrospinal fluid. Three protective membranes, the meninges meninges (mĭnĭn`jēz), three membranous layers of connective tissue that envelop the brain and spinal cord (see nervous system ).
..... Click the link for more information. , wrap the spinal cord and cover the brain—the pia mater is the innermost layer, the arachnoid lies in the middle, and the dura mater is the outside layer, to which the spinal nerves are attached. Connecting with the cord are 31 pairs of these spinal nerves, which feed sensory impulses into the spinal cord, which in turn relays them to the brain. Conversely, motor impulses generated in the brain are relayed by the spinal cord to the spinal nerves, which pass the impulses to muscles and glands. The spinal cord mediates the reflex responses to some sensory impulses directly, i.e., without recourse to the brain, as when a person's leg is tapped producing the knee jerk reflex. Nerve fibers in the spinal cord usually do not regenerate if injured by accident or disease.
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.
spinal cord
..... Click the link for more information. occupying the hollow interior (vertebral canal) of the series of vertebrae that form the spinal column spinal column, bony column forming the main structural support of the skeleton of humans and other vertebrates, also known as the vertebral column or backbone. It consists of segments known as vertebrae linked by intervertebral disks and held together by ligaments.
..... Click the link for more information. , technically known as the vertebral column. Extending from the first lumbar vertebra to the medulla at the base of the brain brain, the supervisory center of the nervous system in all vertebrates. It also serves as the site of emotions, memory, self-awareness, and thought.
Anatomy and Function
..... Click the link for more information. , the spinal cord of a human adult is about 18 in. (45 cm) long. Structurally, the cord is a double-layered tube, roughly cylindrical in cross section. The outer layer consists of white matter, i.e., myelin-sheathed nerve fibers. These are bundled into specialized tracts that conduct impulses triggered by pressure, pain, heat, and other sensory stimuli or conduct motor impulses activating muscles and glands. The inner layer, or gray matter, is primarily composed of nerve cell bodies. Within the gray matter, running the length of the cord and extending into the brain, lies the central canal through which circulates the cerebrospinal fluid. Three protective membranes, the meninges meninges (mĭnĭn`jēz), three membranous layers of connective tissue that envelop the brain and spinal cord (see nervous system ).
..... Click the link for more information. , wrap the spinal cord and cover the brain—the pia mater is the innermost layer, the arachnoid lies in the middle, and the dura mater is the outside layer, to which the spinal nerves are attached. Connecting with the cord are 31 pairs of these spinal nerves, which feed sensory impulses into the spinal cord, which in turn relays them to the brain. Conversely, motor impulses generated in the brain are relayed by the spinal cord to the spinal nerves, which pass the impulses to muscles and glands. The spinal cord mediates the reflex responses to some sensory impulses directly, i.e., without recourse to the brain, as when a person's leg is tapped producing the knee jerk reflex. Nerve fibers in the spinal cord usually do not regenerate if injured by accident or disease.
spinal cord
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Section of a spinal cord. The anterior horn of the gray matter contains cell bodies from which the …
(credit: © Merriam-Webster Inc.)
spinal cord
the thick cord of nerve tissue within the spinal canal, which in man gives rise to 31 pairs of spinal nerves, and together with the brain forms the central nervous system
www.spinalcord.uab.edu
www.spinalcord.org
www.spinalcord.uab.edu
www.spinalcord.org
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