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Lecture7
MotorProcesses
Cogs17*UCSD
ThreeTypesofMuscles
Striate(Skeletal)MuscleConnectedtoTendonstoBones
Voluntarymovements
Cardiac(Heart)MuscleHasendogenousrhythmofactivity,
modifiedbyneurons
Smooth(Organ)MuscleCansustaincontraction,
Mostlyautonomically controlled
SkeletalMuscles
Comein"AntagonisticPairs"
Foreach"FLEXOR"muscle,thatmovesbonestowardbody
Thereisacorresponding"EXTENSOR"muscle,thatmovessamebonesawayfrombody
Neuro-MuscularJunction
MotorNeurons(a orAlphaNeurons)
releaseAcytelcholineontomusclefibers
FiberrespondslikeaNeuronwould!Na+gatesopen,Na+enterscell
ChangeinpolarityopensCa++gatesCa++enterscell…
BUTinsteadofcausingreleaseofneurotransmitter,
Ca++activatesSarcomerestocontract themuscle
Zdisk
Sarcomere ContractileUnitinSkeletalMuscles
Sarcomere
Twokeyproteinsinvolved:Actinand
Myosin
Sarcomere ContractileUnitinSkeletalMuscles
MYOSIN
Cross-Bridges
WhenCa++entersmusclecells,
CrossBridgesactivated
ACTINcoil
SecuredtomuscleatZDisk
They'row' intopairsofActincoils
pullingthemclosertogether
SpinalReflexesSimpleCircuits
StretchReflex
MuscleSpindle(AProprioceptor)inmuscledetects
passivestretchofmuscle
MuscleSpindleexcites
MotorNeuronInSpinalCord
MotorNeuronstimulatessamemuscleto
contract,counterspassivestretch...asfromdoctor'shammer,
orfromshiftofweightwhilewalking
ThisistheONLYone-synapse
reflex
GolgiReflexOver-contractingmusclepullssohardontendonthatthe
GolgiTendonOrgan(aProprioceptor)
signalstheSpinalCord…
activatesanInhibitory Inter-Neuron
inSpinalCordthat…
inhibitsMotorNeuron
tooriginal muscle,reducing contraction
GolgiReflexOver-contractingmusclepullssohardontendon,thatthe
GolgiTendonOrgan(aProprioceptor)signalsSpinalCord
GolgiTendonOrganalso activatesan
Excitatory Inter-NeuroninSpinalCordthat
excitesMotorNeurontoAntagonistic muscle,increasing itscontraction,
whichdecreasesoriginal’scontraction
activatesanInhibitory Inter-Neuron
inSpinalCordthat
inhibitsMotorNeuron
tooriginal muscle,reducing contraction
PainWithdrawalReflex
Nociceptor(PainReceptor)
detectsnoxiousstimulus
NociceptorsynapsesinSpinalCordon
ExcitatoryInter-Neuron
ExcitatoryInter-Neuronexcites
MotorNeuron
MotorNeuroncontractsaflexormuscle
topullsensorawayfromnoxiousstimulus
ScratchReflex
OscillatorCircuit
ACerebellarReflex
SuchcircuitscanbereflexiveORcontrolled
(e.g.clapping)
Likethehuman"Raspberry"
(Tongue/Lipvibration)
InfantReflexes
Babkin ReflexPresspalms,fingersgrasp&mouthopens
Avestigialattempttoclingtofur
ACerebellarReflex
InfantReflexes
RootingReflexTouchcheek,headturns&infantsuckles
CanreappearinVERYdrunkadults,ifcerebellumsuppressedbyalcohol
ACerebellarReflex
Cortico-Spinal(Pyramidal)TractsForcontrolofvoluntary motion,oncontralateral sideofbody
Activatesmotorneuronstocontralateralskeletalmuscles
MostfiberscrosstoContralateral SpinalCord
inMedulla
Corticobulbar Tractforfacemovements
TrigeminalNervetoface
Arm
Face
CrossesoverinthePons
Cortico-SpinalPathwayfromMotorCortex
Ventro-MedialTracts
Primarilyforcontrolofposture,neck,shoulders&trunk,whereonesidecannot
moveseparatelyfromtheother
MakemultipleconnectionsinTectum,VestibularNucleus,ReticularFormation,
integratingwithsensory&arousalsystems
IncludescircuitsforWALKING,sincetwosidesmustbeintightcoordination
Bilateral andIpsi-Lateral
Cerebellum
Cerebellum
MNEMONIC:
Sarah the ballerinahas a hell of a cerebellum!
CerebellumForrapid,well-coordinated movements
requiringprecisetiming
Includepreprogramed(likeSaccades)andlearned-through-practicebehaviors...
...includingshiftsofAttention
Dependonreal-timeSensori-Motorfeedback
PurkinjeCell
CerebellarCircuits
~50BillioncellsinCerebellumalone!
CerebellarCircuits
PurkinjeCells(telephonepoles)
ThiscircuitcodesTIMEasDISTANCEsignalstravel
Sensory&Motorfeedback
ParallelFibers(telephonelines)
Purkinjes correspondtodifferentmusclegroups
Activityalongparalleltractsrepresenttimingofdifferentmoves
bychangesinPurkinjeoutputatdifferentplacesalongarray
DeepNuclei(sendinfoup
motorpathway)
SobrietyTestforCerebellumFunction
Smoothballisticmotionofhandtoface
Walkingastraightline,requiresbalance(integrationofvestibularinput)
CerebellumisparticularlysensitivetoAlcoholpoisoning,
impairingexecutionoftheseactions
BasalGanglia
Striatum
(Input)G.P.
(Output)
OrganizesactivityintoTASKS
A"Re-entrantSystem"thatkeepstrackofstatusof"sub-goals"
"Automates"complexsequentialprocess(e.g.driving) "Selects"what'sappropriatewhen
Pathologiesinclude(OCD)Obscessive CompulsiveDisorder,AttentionDeficitDisorders(ADD)&Parkinson'sdisease
InsufficientDOPAMINEfromSustantia Nigra (inTegmentum)
toStriatum
>>GreaterinhibitionfromGlobusPallidustomotornucleus(VLP)ofThalmus
Producestremors,difficultywithsmoothexecution,cognitivedeficits,eventuallyparalysis&death
Parkinsons'Disease
Treatedwith"L-Dopa",adopamineprecursorthatcrossesblood-brainbarrier
Butmanysideeffects,sinceDopaminesowidespread&multi-functionedinbrain
Canbecausedbyheadtrauma
Butalsotracedtoenvironmentaltoxins!
MotorCortex
MotorCortexPre-CentralGyrus
ATopological
Map
TopologicalCorticalMaps
MotorCortexPre-CentralGyrus
SomatosensoryCortexPost-CentralGyrus
AlignedwithTopologicalMapofbodysurfaceinadjacentSomatosensoryCortex
MotorHumunculus
NotethatHANDSareparticularlymagnified
evencomparedtoSomatosensorymap
Pre-MotorCortexPreparetoact;Planning
Prepareto
Speak
Broca's Area
MirrorCellSystem
"MirrorCells"respondwhensubjectsees/feelsselfperformingfamiliaract
Samecellsrespondwhensubjectseesanother performthatact
Simulationofobservedaction
IntegratedwithactivityofMirrorCellsinParietalLobe
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