vagovagal reflex

vagovagal reflex

[vā′gōvā′gəl]

Etymology: L, vagus + vagus + reflectere, to bend back

a stimulation of the vagus nerve by reflex in which irritation of the larynx or the trachea results in slowing of the pulse rate.

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reflex(es) (rē´fleks),

n a reflected action or movement; the sum total of any specific involuntary activity.

reflex, arc,

n See arc, reflex.

reflex, Breuer,

n.pr See reflex, Hering-Breuer.

reflex, Cheyne-Stokes,

n.pr See respiration, Cheyne-Stokes.

reflex emesis,

n gagging or vomiting induced by touching the mucous membrane of the throat or as a result of other noxious stimuli. Also called
gag reflex.

reflex, Hering-Breuer

n.pr the nervous mechanism that tends to limit the respiratory excursions. Stimuli from the sensory endings in the lungs (and perhaps in other parts) pass up the vagi and tend to limit both inspiration and expiration during ordinary breathing.

reflex, jaw,

n an extension-flexion reflex that is initiated by tapping the mandible downward. The masseter and other elevators of the mandible are the first stretched; then the reflex flexion-contraction elevates the mandible by flexion of elevator muscles while simultaneous stretching (extension) of the depressor muscles of the mandible occurs.

reflex, pharyngeal

n contraction of the constrictor muscles of the pharynx, elicited by touching the back of the pharynx.

reflex, stretch,

n one of the most important features of tonic contraction of muscle. It is the reflex contraction of a healthy muscle that results from a pull. It has been found that stretching a muscle by as little as 0.8% of its original length is sufficient to evoke a reflex response. A stretch of constant degree causes a maintained steady contraction, muscle spindles and stretch receptors in the tendons show very slow adaptation, and the reflex ceases immediately on withdrawal of the stretching force. The stretch reflex is obtained predominantly from those muscles maintaining body posture, among which are the masticating muscles that maintain the position of the mandible and the neck muscles holding the head erect. Together the masticating muscles and neck muscles are responsible for the maintenance of the air and food passages.

reflex, vagovagal

n a reflex in which the afferent and efferent impulses travel via the vagus nerve. The afferent impulses travel centrally via the sensory nucleus of the vagus. The efferent impulses travel via the motor fibers of the vagus nerve.

reflexes, allied,

n.pl reflexes that join to effect a common purpose, such as mastication. They may arise from diverse stimuli, such as smell, taste of food, and texture, shape, and resistance of the food bolus. Collectively, they encourage salivation and a sequence of masticatory closures of the mandible, followed by deglutition.

reflexes, antagonistic,

n.pl reflexes that cannot occupy the final pathway simultaneously. The weaker of these reflexes will give way to the stronger, especially if the latter is a protected reflex (e.g., a hot or nauseating food causes involuntary retching or even vomiting rather than the pleasurable gustatory experience associated with chewing and swallowing tasty food).

reflexes, flexion-extension,

n.pl the reflexes based on the principle of reciprocal innervation. When a voluntary or reflex contraction of a mus-cle occurs, it is accompanied by the simultaneous relaxation of its antagonist. E.g., when the jaw reflex is ini-tiated by tapping the mandible downward, the masseter and other elevators of the mandible are stretched. Then, reflex flexion-contraction of the ele-vators takes place, the mandible is elevated, and the depressor muscles of the mandible are stretched. Many combinations exist, not only between the agonists and the antagonists of a given joint but also between reflexes that cross over to muscle groups of contralateral extremities, joints, and muscles.

reflexes, pathologic,

n.pl reflexes observed in the abnormal or inappropriate motor responses of controlled stimuli initiated in the sensory organ that is appropriate to the reflex arc. They may be initiated in the superficial reflexes of the skin and mucous membrane; in the deep myotatic reflexes of the joints, tendons, and muscles; and in the visceral reflexes of the viscera and other organs of the body. The pathologic reflexes are thus syndromes of abnormal responses to otherwise normal stimuli.