reflex arc
reflex arc
reflex arc
re′flex arc`
n.
Noun | 1. | reflex arc - the neural path of a reflex |
单词 | reflex arc | |||
释义 | reflex arcreflex arcreflex arcre′flex arc`n.
Reflex Arcreflex arc[′rē‚fleks ‚ärk]Reflex Arca group of nerve structures involved in reflex action. The term “reflex arc,” or “nervous arc,” was introduced in 1850 by the British physician and physiologist M. Hall, who was describing the anatomic elements of a reflex. A reflex arc includes (1) receptors, or nerve endings that respond to stimulation; (2) afferent (centripetal) nerve fibers, or the processes of receptor neurons that transmit impulses from sensory nerve endings to the central nervous system; (3) a nerve center, that is, neurons that sense excitation and transmit it to effector neurons through the appropriate synapses; (4) efferent (centrifugal) nerve fibers that transmit excitation from the central nervous system to the periphery; and (5) an effector organ whose activity changes as a result of a reflex. The simplest two-neuron, or monosynaptic, reflex arc consists of receptor and effector neurons separated by a synapse. A multineuron, or polysynaptic, reflex arc consists of a receptor neuron, several internuncial neurons, and an effector neuron, all of which are separated by synapses. A reflex arc does not completely reflect the structure of a reflex because of the proven existence of reverse afference, that is, excitation that informs a nerve center about the condition of an effector organ. V. G. ZILOV reflex arcarc[ahrk]re·flex arcreflex arcreflex arcNeurology The basic conduction pathway through the nervous system, consisting of a sensory neuron, an association neuron, and a motor neuronre·flex arc(rē'fleks ahrk)reflex arcreflex arcthe nervous connections between RECEPTOR and EFFECTOR that result in a simple response being elicited by a specific stimulus (a reflex action), such as a knee jerk without the involvement of the brain. The receptor is excited by a stimulus which induces a nerve impulse in the DENDRITE of a sensory (afferent) NEURONE. This passes through the cell body in the dorsal root ganglion and on along the sensory AXON to the SPINAL CORD. There it crosses a SYNAPSE, usually to an intermediate neurone which synapses with the efferent neurone and passes out of the spinal cord via the ventral root along the axon of the motor (efferent) neurone to the effector which produces the stereotyped response. Most reflexes involve more than one synapse, i.e. are polysynaptic, but those concerned with posture are often monosynaptic, such as the knee-jerk reflex. See Fig. 267 . see RAMUS COMMUNICANS.re·flex arc(rē'fleks ahrk)reflex arc
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