reflex arc

a neural circuit that is involved in a reflex. In its simplest form, it consists of an afferent, or sensory, neuron that conducts nerve impulses from a receptor to the spinal cord, where it connects directly or via an interneuron to an efferent motor neuron that carries the impulses to an effector, that is, a muscle or gland. See also disynaptic arc; monosynaptic arc; polysynaptic arc.

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Psychology term of the day

January 19th 2025

spinal cord

the part of the central nervous system that extends from the lower end of the medulla oblongata, at the base of the brain, through a canal in the center of the spine as far as the lumbar region. In transverse section, the cord consists of an H-shaped core of gray matter (see periaqueductal gray; anterior horn; dorsal horn) surrounded by white matter consisting of tracts of long ascending and descending nerve fibers on either side of the cord that are linked by the white commissure. The spinal cord is enveloped by the meninges and is the origin of the 31 pairs of spinal nerves. See also spinal root.