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POSTURE & EQUILIBRIUM

POSTURE & EQUILIBRIUM. Q -What is posture?. It is maintenance of upright position against gravity (center of body is needed to be between the legs) it needs antigarvity muscles. 1-Up-right posture need postural reflexes. 2- posture depends on muscle tone (

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POSTURE & EQUILIBRIUM

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  1. POSTURE&EQUILIBRIUM Q-Whatisposture? Itismaintenanceofuprightpositionagainst gravity(centerofbodyisneededtobebetweenthe legs)itneedsantigarvitymuscles

  2. 1-Up-rightpostureneedposturalreflexes 2-posturedependsonmuscletone( stretchreflex)(basicposturalreflex) 3-Themainpathwaysconcernedwith postureare:- A-medialtractscontrolproximallimbs& axialmusclesforposture&gross movements 4-lateralpathwaysascorticospinal– rubrospinal)controldistallimbs.

  3. posturalreflexsdependsonthefollowing receptors:- •1-vestibularapparatusreceptorsas •Maculae(utricle&saccule)&SCCcristea. •-Maculaeforlinearacceleration&orientationof headinspace •-SCCcristeaforangularacceleration •2-visual(vision)&auditory(hearing)receptors:- Visioncancompensateforlossofauditory, vestibular&proprioception •-(Tabesdorsalis+veRombergism) •-IfPtwithsensoryataxiastandswitheyesclosed,he falls down) 3-Proprioceptorsofmuscles,tendons,ligaments& joints:-

  4. •a-NeckProprioceptors:- •detectheadpositioninrelationtotrunk •b-BodyProprioceptorsproprioceptorsof anti-gravitymuscles •c-pressurereceptorsasinsoleoffeet initiatepositivesupportingreaction( magnetreflex)

  5. • • -Stretchreflexes&posturalreflexescanbe modifiedbycoordinatedactivity;-      Spinalcord Medulla Midbrain Cerebralcortex cerebellum

  6. Posturalreflexesare:- A-Staticreflexes(atrest) B-Phasicreflexes(with motion)

  7. A-StaticR:- (statotonic):-maintainpostureat rest:- A-spinal B-medullaryreflexes C-Rightingreflexes(midbrain) A-Spinalreflexes:-(CenterinS.C) 1-localstaticreflexes: Positivesupportingreaction(magnetreflex) (receptorsareproprioceptorsofflexors(contraction ofbothflexors&extensors) -protectivereflex 2-Stretchreflex

  8. 3-Segmental staticreflexes:- mediatedbyonesegmentofthespinalcordas:- a-Crossedextensorreflex b-NegativesupportingR(whichrelease+ve supportingreaction-(receptorsareproprioceptorsof extensorsofthereleasedlimb) N.BspinalRcanbestudiedinspinal animalwithcut atneckb/wtheS.C&brainstemsoallS.Cisintact.

  9. •- •B-Medullary staticReflexes •(Center=medullaoblongata)are:- •Neck&labyrinthinereflexes •1-Neckstaticreflexes(studiedina decerebratedanimalcutabovemedulla+ labyrinthdestroyed) •-Stimulusis:-changingheadpositionthat (+)neckproprioceptors

  10. 1--ventroflexionofhead / armsflexion+extendhindlimb( asindecortication). 2-dorsiflexionofhead/ armsextended+flexhindlimb. 3--turningheadtooneside— Extentionoflimbsonthatside+ flexionofotherside.(asin decortication)

  11. •2-labyrinthinestaticreflex:-(in decerebratedanimal)+eliminationof neckproprioceptors)(labyrinthintact) -Receptorsareotolithorgans(maculae) •-Stimulusisgravity 1-ventroflexionofhead(orprone position)-----4limbsflexion 2-dorsiflexionofhead(orsupine position)-----4limbsextended(asin decerebration)

  12. •C-Rightingreflexes:- • (Centerismidbrainexceptthe visualinC.C):- whenuprightpostureisdisturbedasinfalling down •-studiedinadecerebratedanimal(cutabove midbrain=upperdecerebration) • a-visualrightingreflexes( cortical):- -Visualimagecancorrectpositionofhead& bodyifpositionisdisturbed •-centerisc.c- •-stim:visualstim •-receptors;eyereceptors

  13. b-labyrinthinerightingreflexes (midbrain):- (covereyes)&animalheldinairfrom pelvis) -thebodyisnotintheproperposition Asintiltingthehead(+)otolithorgans- >>>>-(+)neckmusclestocorrectthehead level,whenheadisnotinpropersite. receptors;otolithorgans, response;rightingofhead

  14. •Allstaticlabirynthinereflexeshavemaculaasreceptors • • butinstatokineticreflexesduringmotionSCCreceptors. (maculaactinlinear&SCCreceptorsactinangular acceleration)

  15. c-Bodyonheadrightingreflexes(midbrain):-:- Stim:pressureonsideofbody&headisfree receptors;trunkproprieoceptors Response/reflexcorrectionofhead. d-Bodyonbody(midbrain):- Pressureonsideofthebodyandheadisfixed) Receptors/trunkproprieoceptors response/reflexcorrectionofbody

  16. e-Neckrightingreflexes(midbrain):- stim:stretchofneckmuscles (Asifheadiscorrected&bodystilltilted receptors;musclespindlesofneck muscles response;-rightingofshoulders&then rightingofbody.

  17. •B-Phasicreflexes(statokineticreflexes)( centerinC.C):- -maintainpostureduringmotion •a-Hoppingreaction:- • -whenanimalispushedlaterally}}}}}reflexhoppingto keeplimbsinpositiontosupportbody. •Thereceptorsareinmusclespindles. •b-Placingreaction:- -blindfoldedanimalsuspendedinair&movedtowardsa supportingsurface,thefeetswillbeplacedfirmlyonthe supportingsurface(receptorsaretouchreceptors& proprioceptorsinsolesoffeet)

  18. Decerebraterigidity&Decorticaterigidity

  19. Decerebraterigidity:- -Insectionbetweensuperior&inferiorcolliculiofmidbrain (belowthelevelofthered nucleus(e.g.mid-collicularlesion)>>>>blocknormal inhibitorysignalsfrombrain&rednucleusinmidbrainto tonically active pontilereticularformation&Vestibular.Ncausing: 1-Maintainedtonicstaticposturalreflexesthatsupport animalagainstgravity:- a-medullarytonicneck b-medullarylabyrinthineR). 2-AbsentmidbrainrightingR 3-Extensionofhead&4limbsextensors(asin labyrinthinestaticR) -Thejawmaybeclenchedwiththeneckhyperextended duetoincreasedextensortonefromvestibulospinal& reticulospinaltractstoextensormotorneurons 4-spasticity&rigidity&extensioninantigravitymuscles -InhumanbyvascularlesionofbrainstembetweenredN&vestibularnucleus

  20. •Decorticaterigiditymorecommoninhumanthan decerebaterigidity:- 1-lesionincerebralcortexbutbrainstemisintact •aswhatseeninhemiplegicptsafterHgeof internalcapsule •2-Medullarytonicneck&toniclabyrinthine reflexespresent •3-Rightingmidbrainreflexespresent •4-Visualrighting,placing&hoppingreflexeslost

  21. •5-itcausesextensorrigidityinlegs&moderateflexionof armsifheadunturned,assupineposition(tonicneck reflexes) •-thehandsareclenchedintofists,andthelegsextendedand feetturnedinward •2-Turningtheheadtoonesideinitiatestonicneckreflexes e.gturningheadtotheleft>>>>>>>extensionoflimbson leftside&flexionofrightside Cause:- 1-lesionsabovetherednucleussorubrospinalareintacttogetherwithpontine reticulospinalandthevestibulospinalleadstothecharacteristicflexionposturingofthe upperextremitiesandextensorposturingofthelowerextremities. 2-Sincethecorticospinaltractisinterrupted,thepontinereticulospinalandthe vestibulospinalextendL.L 3-normallysuppressorarea4stripintheanterioredgeofprecentralgyrusinhibitred nucleus,ifthisinhibitionislostbydecortication,rednucleusisdisinhibited, disinhibitionofthered nucleusfacilitatetherubrospinal tracttoflexU.L 4-Also/thereislossofinhibitorycorticalsignals(fromsuppressorarea4stripinthe anterioredgeofprecentralgyrus)togammamotorneuronsviareticulospinal

  22. Thankyoufor listening

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