| oculocephalic reflex | Turning of the eyes and head toward the source of an auditory, visual, or other form of stimulation. Synonym: oculocephalic reflex. (05 Mar 2000) |
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| oculocephalogyric reflex | Turning of the eyes and head toward the source of an auditory, visual, or other form of stimulation. Synonym: oculocephalic reflex. (05 Mar 2000) |
| oculovagal reflex | A decrease in pulse rate associated with traction on extraocular muscles or compression of the eyeball; especially sensitive in children; may produce asystolic cardiac arrest. Synonym: Aschner's phenomenon, Aschner's reflex, Aschner-Dagnini reflex, oculovagal reflex. (05 Mar 2000) |
| oesophagosalivary reflex | Salivation caused by irritation of the lower end of the oesophagus, as by carcinoma. Synonym: Roger's reflex. (05 Mar 2000) |
| olecranon reflex | Flexion of the forearm caused by tapping the olecranon. Synonym: paradoxical triceps reflex. (05 Mar 2000) |
| Oppenheim's reflex | Extension of the toes induced by scratching of the inner side of the leg or by following sudden flexion of the thigh on the abdomen and the leg on the thigh; a sign of cerebral irritation. (05 Mar 2000) |
| orbicularis oculi reflex | Contraction of the orbicularis oculi muscles upon tapping the margin of the orbit, or the bridge or tip of the nose. Synonym: nose-bridge-lid reflex, nose-eye reflex. (05 Mar 2000) |
| orbicularis pupillary reflex | A constriction of both pupils when an effort is made to close eyelids forcibly held apart. A variant of the pupil response to near vision. Synonym: Galassi's pupillary phenomenon, Gifford's reflex, lid-closure reaction, orbicularis phenomenon, orbicularis pupillary reflex, Piltz sign, Westphal's pupillary reflex, Westphal-Piltz phenomenon. (05 Mar 2000) |
| orienting reflex | An aspect of attending in which an organism's initial response to a change or to a novel stimulus is such that the organism becomes more sensitive to the stimulation; e.g., dilation of the pupil of the eye in response to dim light. Synonym: investigatory reflex, orienting response. (05 Mar 2000) |
| tapetal light reflex | The glow from the eyes of some animals in the dark when a light illuminates the retina; due to the reflection of the light from the tapetum, an iridescent layer (containing guanidine crystals) in the choroid. (05 Mar 2000) |
| tarsophalangeal reflex | Extension of all the toes except the first, when the outer part of the tarsus is tapped; in certain cerebral diseases the reverse takes place, the toes being flexed. (05 Mar 2000) |
| tendo Achillis reflex | A contraction of the calf muscles when the tendo calcaneus is sharply struck. Synonym: ankle jerk, ankle reflex, tendo Achillis reflex, triceps surae reflex. (05 Mar 2000) |
| tendon reflex | A myotatic or deep reflex in which the muscle stretch receptors are stimulated by percussing the tendon of a muscle. (05 Mar 2000) |
| thumb reflex | Flexion of the thumb upon tapping the dorsum of the hand. Synonym: metacarpothenar reflex. (05 Mar 2000) |
| elbow reflex | A sudden contraction of the triceps muscle caused by a smart tap on its tendon when the forearm hangs loosely at a right angle with the arm. Synonym: elbow jerk, elbow reflex. (05 Mar 2000) |