Reflex (redirected from reflexes)

reflex /re·flex/ (re´fleks) a reflected action or movement; the sum total of any particular automatic response mediated by the nervous system.

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abdominal reflexes  contractions of the abdominal muscles on stimulation of the abdominal skin.

accommodation reflex  the coordinated changes that occur when the eye adapts itself to near vision; constriction of the pupil, convergence of the eyes, and increased convexity of the lens.

Achilles tendon reflex  triceps surae r.

acoustic reflex  contraction of the stapedius muscle in response to intense sound.

anal reflex  contraction of the anal sphincter on irritation of the anal skin.

ankle reflex  triceps surae r.

auditory reflex  any reflex caused by stimulation of the vestibulocochlear nerve, especially momentary closure of both eyes produced by a sudden sound.

Babinski's reflex  dorsiflexion of the big toe on stimulation of the sole, occurring in lesions of the pyramidal tract, although a normal reflex in infants.

Babkin reflex  pressure by the examiner's thumbs on the palms of both hands of the infant results in opening of the infant's mouth.

baroreceptor reflex  the reflex response to stimulation of baroreceptors of the carotid sinus and aortic arch, regulating blood pressure by controlling heart rate, strength of heart contractions, and diameter of blood vessels.

Bezold reflex , Bezold-Jarisch reflex reflex bradycardia and hypotension resulting from stimulation of cardiac chemoreceptors by antihypertensive alkaloids and similar substances.

biceps reflex  contraction of the biceps muscle when its tendon is tapped.

Brain's reflex  extension of a hemiplegic flexed arm on assumption of a quadrupedal posture.

brain stem reflexes  those regulated at the level of the brain stem, such as pupillary, pharyngeal, and cough reflexes, and the control of respiration; their absence is one criterion of brain death.

bulbospongiosus reflex  contraction of the bulbospongiosus muscle in response to a tap on the dorsum of the penis.

carotid sinus reflex  slowing of the heart beat on pressure on the carotid artery at the level of the cricoid cartilage.

Chaddock's reflex  in lesions of the pyramidal tract, stimulation below the external malleolus causes extension of the great toe.

chain reflex  a series of reflexes, each serving as a stimulus to the next one, representing a complete activity.

ciliary reflex  the movement of the pupil in accommodation.

ciliospinal reflex  dilation of the ipsilateral pupil on painful stimulation of the skin at the side of the neck.

closed loop reflex  a reflex, such as a stretch reflex, in which the stimulus decreases when it receives feedback from the response mechanism.

conditioned reflex  see under response.

conjunctival reflex  closure of the eyelid when the conjunctiva is touched.

corneal reflex  closure of the lids on irritation of the cornea.

cough reflex  the events initiated by the sensitivity of the lining of the airways and mediated by the medulla as a consequence of impulses transmitted by the vagus nerve, resulting in coughing.

cremasteric reflex  stimulation of the skin on the front and inner thigh retracts the testis on the same side.

deep reflex  tendon r.

digital reflex  Hoffmann's sign (2).

diving reflex  a reflex involving cardiovascular and metabolic adaptations to conserve oxygen occurring in animals during diving into water; observed in reptiles, birds, and mammals, including humans.

elbow reflex  triceps r.

embrace reflex  Moro's r.

finger-thumb reflex  opposition and adduction of the thumb combined with flexion at the metacarpophalangeal joint and extension at the interphalangeal joint on downward pressure of the index finger.

gag reflex  pharyngeal r.

gastrocolic reflex  increase in intestinal peristalsis after food enters the empty stomach.

gastroileal reflex  increase in ileal motility and opening of the ileocecal valve when food enters the empty stomach.

grasp reflex  flexion or clenching of the fingers or toes on stimulation of the palm or sole, normal only in infancy.

Hering-Breuer reflex  the reflex that limits excessive expansion and contraction of the chest during respiration prior to sending impulses to the brain via the vagus nerve.

Hoffmann's reflex  see under sign (2).

hypogastric reflex  contraction of the muscles of the lower abdomen on stroking the skin on the inner surface of the thigh.

jaw reflex , jaw jerk reflex closure of the mouth caused by a downward blow on the passively hanging chin; rarely seen in health but very noticeable in corticospinal tract lesions.

knee jerk reflex  patellar r.

light reflex 

1. cone of light.

2. contraction of the pupil when light falls on the eye.

3. a spot of light seen reflected from the retina with the retinoscopic mirror.

Magnus and de Kleijn neck reflexes  extension of both ipsilateral limbs, or one, or part of a limb, increase of tonus on the side to which the chin is turned when the head is rotated to the side, and flexion with loss of tonus on the side to which the occiput points; sign of decerebrate rigidity except in infants.

Mayer's reflex  finger-thumb r.

Mendel-Bekhterev reflex  dorsal flexion of the second to fifth toes on percussion of the dorsum of the foot; in certain organic nervous disorders, plantar flexion occurs.

micturition reflex  any of the reflexes necessary for effortless urination and subconscious maintenance of continence.

Moro's reflex  flexion of an infant's thighs and knees, fanning and then clenching of fingers, with arms first thrown outward and then brought together as though embracing something; produced by a sudden stimulus and seen normally in the newborn.

myotatic reflex  stretch r.

neck reflexes  reflex adjustments in trunk posture and limb position caused by stimulation of proprioceptors in the neck joints and muscles when the head is turned, tending to maintain a constant orientation between the head and body.

neck righting reflex  rotation of the trunk in the direction in which the head of the supine infant is turned; this reflex is absent or decreased in infants with spasticity.

nociceptive reflexes  reflexes initiated by painful stimuli.

oculocardiac reflex  a slowing of the rhythm of the heart following compression of the eyes; slowing of from 5 to 13 beats per minute is normal.

open loop reflex  a reflex in which the stimulus causes activity that it does not further control and from which it does not receive feedback.

Oppenheim reflex  dorsiflexion of the big toe on stroking downward along the medial side of the tibia, seen in pyramidal tract disease.

orbicularis oculi reflex  normal contraction of the orbicularis oculi muscle, with resultant closing of the eye, on percussion at the outer aspect of the supraorbital ridge, over the glabella, or around the margin of the orbit.

orbicularis pupillary reflex  unilateral contraction of the pupil followed by dilatation after closure or attempted closure of eyelids that are forcibly held apart.

palatal reflex , palatine reflex stimulation of the palate causes swallowing.

patellar reflex  contraction of the quadriceps and extension of the leg when the patellar ligament is tapped.

peristaltic reflex  when a portion of the intestine is distended or irritated, the area just proximal contracts and the area just distal relaxes.

pharyngeal reflex  contraction of the pharyngeal constrictor muscle elicited by touching the back of the pharynx.

pilomotor reflex  the production of goose flesh on stroking the skin.

placing reflex  flexion followed by extension of the leg when the infant is held erect and the dorsum of the foot is drawn along the under edge of a table top; it is obtainable in the normal infant up to the age of six weeks.

plantar reflex  irritation of the sole contracts the toes.

proprioceptive reflex  one initiated by a stimulus to a proprioceptor.

pupillary reflex 

1. contraction of the pupil on exposure of the retina to light.

2. any reflex involving the iris, resulting in change in the size of the pupil, occurring in response to various stimuli, e.g., change in illumination or point of fixation, sudden loud noise, or emotional stimulation.

quadriceps reflex  patellar r.

quadrupedal extensor reflex  Brain's r.

red reflex  a luminous red appearance seen upon the retina in retinoscopy.

righting reflex  the ability to assume an optimal position when there has been a departure from it.

Rossolimo's reflex  in pyramidal tract lesions, plantar flexion of the toes on tapping their plantar surface.

scratch reflex  a spinal reflex by which an itch or other irritation of the skin causes a nearby body part to move over and briskly rub the affected area.

spinal reflex  any reflex action mediated through a center of the spinal cord.

startle reflex  Moro's r.

stepping reflex  movements of progression elicited when the infant is held upright and inclined forward with the soles of the feet touching a flat surface.

stretch reflex  reflex contraction of a muscle in response to passive longitudinal stretching.

sucking reflex  sucking movements of the lips of an infant elicited by touching the lips or the skin near the mouth.

superficial reflex  any withdrawal reflex elicited by noxious or tactile stimulation of the skin, cornea, or mucous membrane, including the corneal reflex, pharyngeal reflex, cremasteric reflex, etc.

swallowing reflex  palatal r.

tendon reflex  one elicited by a sharp tap on the appropriate tendon or muscle to induce brief stretch of the muscle, followed by contraction.

tonic neck reflex  extensions of the arm and sometimes of the leg on the side to which the head is forcibly turned, with flexion of the contralateral limbs; seen normally in the newborn.

triceps reflex  contraction of the belly of the triceps muscle and slight extension of the arm when the tendon of the muscle is tapped directly, with the arm flexed and fully supported and relaxed.

triceps surae reflex  plantar flexion caused by a twitchlike contraction of the triceps surae muscle, elicited by a tap on the Achilles tendon, preferably while the patient kneels on a bed or chair, the feet hanging free over the edge.

Triceps surae reflex.

vestibular reflexes  the reflexes for maintaining the position of the eyes and body in relation to changes in orientation of the head.

vestibuloocular reflex  nystagmus or deviation of the eyes in response to stimulation of the vestibular system by angular acceleration or deceleration or when the caloric test is performed.

withdrawal reflex  a nociceptive reflex in which a body part is quickly moved away from a painful stimulus.

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re·flex (rflks)

n.

1. An involuntary physiological response to a stimulus.

2. An unlearned or instinctive response to a stimulus.

3. Something, such as light or heat, that is reflected.

adj.

1. Being an involuntary action or response, such as a sneeze, blink, or hiccup.

2. Bent, turned, or thrown back; reflected.

v. (r-flks)

1. To cause to undergo a reflex process.

2. To reflect.

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Reflex

A response, usually a movement, elicited by tapping on the nerve with a special hammer-like instrument.

Mentioned in: Neurogenic Bladder, Neurologic Exam, Physical Examination

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reflex,

n an automatic, predictable and adaptive neuromuscular response to a stimuli.

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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.

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reflex

a reflected involuntary action or movement; the sum total of any particular automatic response mediated by the nervous system.

A reflex is built into the nervous system and does not need the intervention of conscious thought to take effect.

For reflexes used in clinical examination of a patient see under individual titles including anal, blink, corneal, conjunctival, crossed extensor, extensor thrust, eyelid, gastrocnemius, hopping, palpebral, panniculus, patellar, perineal, placing, pupillary, withdrawal.

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accommodation reflex

the coordinated changes that occur when the eye adapts itself for near vision; they are constriction of the pupil, convergence of the eyes and increased convexity of the lens.

reflex action

an involuntary response to a stimulus conveyed to the nervous system and reflected to the periphery (see also reflex).

reflex bradycardia

bradycardia occurring as a reflex initiated by severe atrial or ventricular stretch.

chain reflex

a series of reflexes, each serving as a stimulus to the next, making a complete activity.

complete reflex

one requiring no feedback from the forebrain.

conditioned reflex

see conditioned response.

cutaneous trunci reflex

see panniculus reflex.

dazzle reflex

a test of the retina, optic nerve, and central retinal pathways. Shining a bright light into the eye should cause squinting.

reflex dyssynergia

see detrusor-urethral dyssynergia.

gastroileal reflex

increase in ileal motility and opening of the ileocecal valve when food enters the empty stomach.

light reflex

see pupillary light reflex.

nociceptive reflex

reflexes initiated by painful stimuli.

palatal reflex

see swallowing reflex.

rectosphincteric reflex

relaxation of the anal sphincter which occurs with distention of the rectum and during defecation.

stepping reflex

movements of progression elicited when the animal is held upright and inclined forward with the feet touching a flat surface.

stretch reflex

reflex contraction of a muscle in response to passive longitudinal stretching.

superficial reflex

any withdrawal reflex elicited by noxious or tactile stimulation of the skin, cornea or mucous membrane, including the corneal and pharyngeal reflexes.

tapetal reflex

tapetal reflection of light.

tendon reflex

a method of testing the patency of reflex arc. The tendon is stretched sharply by tapping it close to its insertion. A positive reaction is a sharp contraction of the muscle of which the tendon is part. The patellar reflex is the best known of these reflexes. Absence indicates a defect in the reflex arc, an exaggerated response suggests an upper motor neuron lesion. Called also myotactic reflex.

tonic reflex

see tonic neck response.

triceps surae reflex

Achilles reflex.

trigemino-abducens reflex

a test of the ophthalmic and mandibular divisions of the trigeminal nerve, and the abducens nerve. Light touching of the cornea should result in retraction of the globe and protrusion of the nictitating membrane.

reflex walking

spinal reflexes can provide support and uncoordinated use of the hindlegs that resembles walking, in dogs with transection of the spinal cord between T13 and L4.

whisker reflex

pinching the pinna elicits a twitch of the whiskers in cats; used in assessment of depth of anesthesia.