Reflex Arc


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reflex arc

[′rē‚fleks ‚ärk]
(neuroscience)
A chain of neurons composing the anatomical substrate or pathway of the unconditioned reflex.

Reflex Arc

 

a 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

References in periodicals archive ?
33) John Dewey, "The Reflex Arc Concept in Psychology," Psychological Review 3, no.
13-21) The denervation of the cornea during the procedure is the cause for the post-operative decrease in corneal sensitivity and results in the disruption to the tear reflex arc.
Depending on the number of synapses interposed on the trajectory reflex arc, reflexes are monosynaptic and polysynaptic.
In this way, Bode modified the behaviorist model of a reflex arc further than Dewey had.
The role of sinoaortic and cardiopulmonary baroreceptor reflex arcs in nocioception and stress-induced analgesia.
The presence of an anal wink and bulbocavemosus reflex suggests an intact S2 through S4 reflex arc.
Recognizing that the brainstem is part of the hiccup reflex arc, Dr.
Of particular note is the author's painstaking narrative of the developments that led up to Dewey's famous essay "The Reflex Arc Concept in Psychology," which was published in 1896 and is now regarded as one of the great documents in the history of psychology.
Researchers at Ben-Gurion University of the Negev, Beer-Sheva, Israel, speculated that the sympathetic stimulus of ejaculation might have terminated the reflex arc that caused the hiccups.
Precise, chiropractic adjustments of these segments improves range of motion, decreases inflammation and pain, and stimulates mechanoreceptors which, through a tonic reflex arc, relax the muscles of the thoracic outlet.
One theory states that following injury, a reflex arc --a loop or circle involving various elements of the peripheral nervous system --is established.