Reflex Arc

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reflex arc

[′rē‚fleks ‚ärk]
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.


References in periodicals archive ?
HRL values are dependent on the increase in the length of reflex arc with height, and the maturation/myelination of nerve fiber from birth to 6 months of age.
(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. (17,21,22) During recovery, a decrease in lacrimal gland secretion results in dry eye symptoms for the patient (29) These dry eye symptoms are compounded further by the loss of goblet cells thought to be a result of damage caused by the suction ring during flap creation.
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.
Thus, based on these data, we assumed that exposure to wDE would not only cause immediate exposure-related physiological changes (not measured) but also sensitize the airway autonomic reflex arc (Figure 4), resulting in autonomic imbalance and increased sensitivity to developing arrhythmia.
Activation of the sinoaortic baroreceptor reflex arc induces analgesia: interaction between cardiovascular and endogenous pain inhibition systems.
(1,2) Disruption of this neuronal pathway affects the reflex arc that controls fine voluntary movements, resulting in signs and symptoms such as palatal myoclonus and dentatorubral tremor.
Here German and American scholars of philosophy discuss that connection from such perspectives as the diversity of subjects in his philosophy, the dialogue between pragmatism and constructivism in historical perspective, from the reflex arc concept to social constructivism, pragmatist and constructivist theories of the observer, and the theory of culture.
The neural reflex arc is the simplest and most familiar type of stimulus-response system (Figures 6-2a and 6-3).
The strength of the levator ani muscles and sacral reflex arc should be tested.