Final Voluntry Movement

8/14/2019 Final Voluntry Movement

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VOLUNTRYVOLUNTRY

MOVEMENTMOVEMENT


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REM EMB EREM EMB ER Every voluntary movement requires posturalEvery voluntary movement requires postural

adjustment which are mostly automatic & makeadjustment which are mostly automatic & make

use of reflexes .use of reflexes .

Complex movements (walking) involveComplex movements (walking) involve

complicated sequences which are controlledcomplicated sequences which are controlled

without conscious attention although can bewithout conscious attention although can bevoluntarily interrupted & other movements canvoluntarily interrupted & other movements can

superimposed upon them .superimposed upon them .


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WHERE I S VOL UNT RYHERE I S VOL UNT RYMO VEME NTO VEME NTINI TI ATED ?NI TI ATED ?

Large areas of cerebral cortex are devoted toLarge areas of cerebral cortex are devoted tofine movements of hand , mouth , tongue &fine movements of hand , mouth , tongue &feet .feet .

Large conspicuous pathway from a part ofLarge conspicuous pathway from a part ofcerebral cortex , just anterior to the centralcerebral cortex , just anterior to the centralsulcus , into the brain stem & so on to thesulcus , into the brain stem & so on to the

spinal cord .spinal cord .

Lesions in the motor area were known to resultLesions in the motor area were known to resultin profound disturbances of movementin profound disturbances of movement


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PI EC ES TO B EI EC ES TO BEC O LL ECTED & PAR TS TOO LL ECTED & PAR TS TO

BE INTEG R ATE DE INTEG R ATE D The large motor pathway running from the cortex intoThe large motor pathway running from the cortex into

the spinal cord is calledthe spinal cord is called PYRAMIDAL TRACTPYRAMIDAL TRACTafter the pyramid = a cone shaped structure in theafter the pyramid = a cone shaped structure in the

brain stem , all other pathways involved in movementbrain stem , all other pathways involved in movementare calledare called EXRAPYRAMIDALEXRAPYRAMIDAL

Most of the large pyramidal shaped cells in the motorMost of the large pyramidal shaped cells in the motor

cortex were connected polysynaptically through chainscortex were connected polysynaptically through chainsof excitatory & inhibitory neurons to the extrafusalof excitatory & inhibitory neurons to the extrafusalalpha motor neurons.alpha motor neurons.


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About 10% of the pyramidal tract fibers in primate areAbout 10% of the pyramidal tract fibers in primate areconnected monosynaptically to extrafusal fibers .connected monosynaptically to extrafusal fibers .

Monosynaptic pathway is thought to be of special useMonosynaptic pathway is thought to be of special usefor rapid voluntary movement of the hand .for rapid voluntary movement of the hand .

When very careful lesions were made in pyramidalWhen very careful lesions were made in pyramidal

tracts in monkeys ,tracts in monkeys , only the finest of fingeronly the finest of fingermovement were lost especially those of the thumbmovement were lost especially those of the thumb& index finger while great variety of voluntary& index finger while great variety of voluntarymovements remained .movements remained .

Before movements begin from a motor control centre ,Before movements begin from a motor control centre ,the pyramidal tract neurons discharge action potentialsthe pyramidal tract neurons discharge action potentials50 100 msec before movement .50 100 msec before movement .


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WHAT ARE TH E F UNCTIO NS OFHAT ARE TH E F UNCTIO NS OFOTHER BRAIN ST RUCTURES K NOW NTHER BRAIN ST RUCTURES K NOW N

TO BE INVOLVED IN MOV EMENT ?O BE INVOLVED IN MOV EMENT ? Cerebellum & basal ganglia play aCerebellum & basal ganglia play a

subsidiary but important role in thesubsidiary but important role in the

control of voluntary movement .control of voluntary movement .

Movements are not elicited onMovements are not elicited on

stimulation of the above structures BUTstimulation of the above structures BUTprofound movement disturbances occurprofound movement disturbances occur

when they are damaged or diseased .when they are damaged or diseased .


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IN TE G RAT IO NN TE G RAT IO N Movement is initiated by the entire motorMovement is initiated by the entire motor

nervous system & no centre is above thenervous system & no centre is above the

others or control the rest but coordinatedothers or control the rest but coordinatedsensible voluntary movement is initiatedsensible voluntary movement is initiated

by the concerted integrated action of theby the concerted integrated action of the

cerebellum , motor cortex , basal gangliacerebellum , motor cortex , basal ganglia& all other areas of pyramidal & extra& all other areas of pyramidal & extra

pyramidal systems .pyramidal systems .


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CEREB ELL UEREB ELL UM Cerebellum might supply feed back informationCerebellum might supply feed back information

mainly from joints & muscle receptors to themainly from joints & muscle receptors to the

motor cortex .motor cortex .

Functionally , it consists of a midline portionFunctionally , it consists of a midline portion

( lesions affect balance & equilibrium ) & lateral( lesions affect balance & equilibrium ) & lateral

portion ( more involved with voluntaryportion ( more involved with voluntarymovement =movement = 1-decreased muscle tone1-decreased muscle tone,,2- late2- late

inin startingstarting,,3- not accurately terminated3- not accurately terminated ) .) .


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In summary , the lateral lobe & nuclei of theIn summary , the lateral lobe & nuclei of thecerebellum appear to assist in ordering thecerebellum appear to assist in ordering the

sequence of contraction in different muscles &sequence of contraction in different muscles &to ensure that contraction occurs at the rightto ensure that contraction occurs at the rightmoment during voluntary movement .moment during voluntary movement .

Cerebellum receives an advance report ofCerebellum receives an advance report ofactivity in the pyramidal tract . Proprioceptiveactivity in the pyramidal tract . Proprioceptiveinformation processed by the cerebellar cortexinformation processed by the cerebellar cortexinfluences & modifies the output of theinfluences & modifies the output of the

cerebellar nuclei & subsequently the motorcerebellar nuclei & subsequently the motorcenters & plays an important role in thecenters & plays an important role in thecoordination of voluntary movement .coordination of voluntary movement .


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B ASA LASA LGANGL IAANGL IA Lesions in it result in purposelessLesions in it result in purposeless

unwanted movements .unwanted movements .

In animals , it is the major motor centreIn animals , it is the major motor centre


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MOTO ROTO RC OR T EXOR T EX Somatic representation in the motor cortexSomatic representation in the motor cortex

shows that the upper most part of it containsshows that the upper most part of it containsneurons that supply the leg & footneurons that supply the leg & foot

musculatures while the lower part of it suppliesmusculatures while the lower part of it suppliesthe face & tongue . The main output from it isthe face & tongue . The main output from it isfrom the pyramidal shaped cells which projectfrom the pyramidal shaped cells which projectto both pyramidal & extrapyramidal pathways .to both pyramidal & extrapyramidal pathways .This is in part explains the profound paralysisThis is in part explains the profound paralysis

which results from destruction motor cortexwhich results from destruction motor cortexwhile pyramidal tract damage results only inwhile pyramidal tract damage results only inloss of very fine movementsloss of very fine movements


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Final Voluntry Movement