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Contents Introduction Reflex arc Classification of reflexes Significance of reflexes Types of reflexes Conclusion
Introduction A reflex is an involuntary or automatic action that yourbody does in response to something without evenhaving to think about it Neonatal reflexes – inborn reflexes present at birth &occur in a predictable fashion Normally developing newborn should respond tocertain stimuli with these reflexes
Reflex arc Anatomical pathway for a reflex iscalled as reflex arc It has 5 components : Receptor Afferent nerve Center Efferent nerve Effector organ
Classification of reflexes Depending upon whether inborn or acquired Unconditioned reflexes, inborn reflex Conditioned reflexes/acquired reflexes
Depending upon the situation of the center Cerebellar reflexes Cortical reflex Midbrain reflex Bulbar or medullary reflexes Spinal reflexes
Depending upon the purpose Protective/flexor reflexes Antigravity/extensor reflexes Depending upon clinical basis Superficial reflexes Mucus membrane Cutaneous reflex Deep reflexes Visceral reflexes Pathological reflexes
Significance of reflexes Helps a paedodontist to identify whether the child isdeveloping normally or not Tells about what abnormalities the child may behaving if all reflexes are not proper Knowledge of development of motor skills – helps toidentify whether development is going on at a properrate or not
General body reflexes Moro reflex/ startle reflex Begins at 28 weeks of gestation Initiated by any sudden movement ofthe neck Elicited by -- pulling the baby halfwayto sitting position from supine &suddenly let the head fall back Consists of rapid abduction & extensionof arms with the opening of hands,tensing of the back muscles, flexion ofthe legs and crying
Within moments, the arms come together again Clinical significanceIts nature gives an indication of muscle toneFailure of the arms to move freely or the hands to openfully indicates hypotonia.It fades rapidly and is not normally elicited after 6months of age.
Palmar/grasp reflex Begins at 32 weeks of gestation Light touch of the palm producesreflex flexion of the fingers Most effective way -- slide thestimulating object, such as a fingeror pencil, across the palm from thelateral border Disappears at 3-4 months Replaced by voluntary grasp at 45months
Clinical significance Exceptionally strong grasp reflex -- spastic form of cerebralpalsy & Kernicterus May be asymmetrical in hemiplagia & in cases of cerebraldamage Persistence beyond 3-4 months indicate spastic form ofpalsy
Plantar/grasp reflex Placing object or finger beneath thetoes causes curling of toes around theobject Present at 32 weeks of gestation Disappears at 9-12 months• Clinical significance : This reflex is referred to as the"readiness tester". Integrates at the same time thatindependent gait first becomespossible.
Walking/steppingreflex When sole of foot is pressedagainst the couch, baby tries towalk Legs prance up & down as if babyis walking or dancing Present at birth, disappears atapprox 2-4 months With daily practice of reflex,infants may walk alone at 10months
Clinical significancePremature infants will tend to walk in a toe-heelfashion while more mature infants will walk in aheel-toe pattern.
Limb placement reflex When the front of the leg below theknee or the arm below the elbow isbrought into contact with the edgeof a table, child lifts the limbs overthe edge Present at birth, fades away rapidlyin early months of life• Clinical significance Reflex is readily demonstrable in thenewborn and persistent failure toelicit it at this stage, is thought toindicate neurological abnormality
Withdrawal reflex Protective reflex Stimulus : a pinprick or a sharppainful stimulus to sole of foot Response : flexion & withdrawal ofstimulated leg Present at birth, persists throughoutlife Clinical significance – Absence ofthis is seen in neurologically impairedinfants.
Asymmetric tonic neck reflex Most evident between 2-3 months of age• Clinical significance The reflex fades rapidly and is not normallyseen after 6 months of age. Persistence is the most frequently observedabnormality of the infantile reflexes ininfants with neurological lesions Greatly disrupts development
Symmetric tonic neckreflex Extension of the head causesextension of the fore limbs andflexion of the hind limbsEvident between 2-3 months of age Clinical significance Not normally easily seen or elicited innormal infants May be seen in an exaggerated formin many children with cerebral palsy.
Babinski’s reflex Stimulus consists of a firm painful strokealong the lateral border of the sole from heelto toe Response consists of movement (flexion orextension) of the big toe and sometimesmovement (fanning) of the other toes Present at birth, disappears at approx 9-10months Presence of reflex later may indicate disease
Babkin reflex Deep pressure applied simultaneouslyto the palms of both hands while theinfant is in supine position Stimulus is followed by flexion orforward bowing of the head, opening ofthe mouth and closing of the eyes Fades rapidly and normally cannot beelicited after 4 months of age.
• Clinical significance Reflex can be demonstrated in the newborn, thus showinga hand-mouth neurological link, even at that early stage
Parachute reflex Reflex appears at about 6-9 months &persists thereafter Elicited by holding the child in ventralsuspension & suddenly lowering him to thecouch Arms extend as a defensive reaction• Clinical significance Absent or abnormal in children withcerebral palsy Would be asymmetrical in spastichemiplagia
Landau reflex Seen in horizontal suspension with thehead, legs & spine extended If the head is flexed, hip knees &elbows also flex Appears at approximately 3 months,disappears at 12-24 months• Clinical significance Absence of reflex occurs in hypotonia,hypertonia or mental abnormality
Trunk incurvation reflex Stroking one side of spinal columnwhile baby is on his abdomen causes Crawling motion with legs Lifting head from surface Present in utero, seen atapproximately 3rd or 4th day Persists for 2-3 months
Gallant’s reflex Firm sharp stimulation along sides ofthe spine with the fingernails or a pinproduces contraction of the underlyingmuscles and curving of the back. Response is easily seen when the infantis held upright and the trunkmovement is unrestricted Best seen in the neonatal period andthereafter gradually fades.
Tendon reflexes Simple monosynaptic reflexes, which are elicited by asudden stretch of a muscle tendonOccurs when the tendon is tappedPresent throughout life
Clinical significance Useful diagnostically for :Detection of upper motor neuron lesions (exaggeratedresponse)Myopathic conditions (depressed or absent response)Localization of the segmental lesions of the cord.
Tonic labyrinthine reflex Labyrinths -- most important organsconcerned with the development ofanti-gravity postures and balance Movement of the head in anydimension stimulates the labyrinths;and produces the appropriateresponses Arms & legs extend when head movesbackwards, & will curl in when thehead moves forward Emerges in utero until approximately4 months postnatally
Facial reflexes Nasal reflex Stimulation of the face or nasal cavity with water or localirritants produces apnea in neonates Breathing stops in expiration with laryngeal closure ininfants – bradycardia & lowering of cardiac output Blood flow to skin, splanchnic areas muscles & kidneydecreases Flow to the heart & brain remains protected
Blink reflex A bright light suddenly shone into the eyes, a puff of airupon the sensitive cornea or a sudden loud noise willproduce immediate blinking of the eyes Purpose – to protect the eyes from foreign bodies & brightlight May be associated tensing of the neck muscles, turning ofthe head away from the stimulus, frowning and crying Reflexes are easily seen in the neonate and continue to bepresent throughout life
Clinical significance Examination is a part of some neurological exams,particularly when evaluating comaSatisfactory demonstration of these reflexes indicate – No cerebral depression Contraction of appropriate muscles in response
Doll’s eye reflex(Oculocephalic reflex) Passive turning of the head ofthe newborn leaves the eye“behind” A distinct time lag occurs beforethe eyes move to a new positionin keeping with the head position Disappears at within a week ortwo of birth Failure of this reflex to appearindicates a cerebral lesionHeadEye
Auditory orienting reflex A sudden loud and unpleasant noise : May produce the blink reflex Infant may remain still and show increased alertness Quieter sounds usually cause reflex eye and head turning to theside of the sound, as if to locate it Seen first at about 4 months of age Thereafter, head turning towards sound stimuli occurs and theaccuracy of localization increases rapidly by 9-10 months
Clinical significance Reflex responses are made use of in tests of infants forhearing loss Pattern of the localization responses indicates the level ofneurological maturity
Oral reflexes Rooting reflex Baby’s cheek is stroked : They respond by turning their headtowards the stimulus They start sucking, thus allowing forbreast feeding When corner of mouth is touched, lowerlip is lowered, tongue moves towards thepoint stimulated When finger slides away, head turns tofollow it When center of lip is stimulated, lipelevates
Onset -- 28 weeks IU Well established – 32-34 weeks IU Disappears – 3-4 months Clinical significancePersistence can interfere with sucking Absence of this is seen in neurologically impairedinfants.
Sucking / Swallowingreflex Touching lips or placing something inbaby’s mouth causes baby to drawliquid into mouth by creating vacuumwith lips, cheeks & tongue Onset – 28 weeks IU Well established – 32-34weeks IU Disappears around 12 months
Clinical significance :Persistence may inhibit voluntary suckingSigmund Freud - Any kind of deprivation of theactivity will lead to fixation resulting in oral habits
Gag reflex(Pharyngeal reflex) Seen in 19 weeks of IU life Reflex contraction of the backof the throat Evoked by touching the roof ofthe mouth, the back of thetongue, the area around thetonsils and the back of thethroat
Functional significance It, along with reflexive pharyngeal swallowing, preventssomething from entering the throat except as part ofnormal swallowing and helps prevent choking Clinical significance Absence of the gag reflex -- symptom of a number ofsevere medical conditions : Damage to the glossopharyngeal nerve, the vagus nerve, Brain death.
Cry reflex Non conditioned reflex whichaccounts for its lack of itsindividual character Sporadic in nature Starts as early as 21-29 weeks of IUlife
Importance of cry It is infant’s first verbal communication Can be interpreted as a message of urgency or distress Indicates: Hunger Pain Discomfort
ConclusionAppropriate knowledge of reflexes enables a paedodontist to identify whether the child is developing normally ornot to identify whether development is going on at a properrate or not Knowledge of abnormalities if all reflexes are not proper
References Shobha Tandon. Textbook of Paedodontics MS Muthu. Paediatric Dentistry, Principals & practice