Motor System Student Handout 08.05.23.pdf

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1. MOTOR
SYSTEM 3
DR SARAN AJAY
DEPT. OF PHYSIOLOGY, GMCM

2. DEPT. OF PHYSIOLOGY, GMCM 2
INPUT OUTPUT

3. DEPT. OF PHYSIOLOGY, GMCM 3
MOTOR OUTPUT
VOLUNTARY MOVEMENTS
REFLEXES
RHYTHMIC MOVEMENTS

4. VOLUNTARY MOVEMENTS
DEPT. OF PHYSIOLOGY, GMCM 4

5. DEPT. OF PHYSIOLOGY, GMCM 5

6. •Commands forvoluntarymovementsoriginatein
corticalassociationareas.
•Planningandorganizationofmovements→bycortex,
basalgangliaandlateralportionofcerebellum
DEPT. OF PHYSIOLOGY, GMCM 6

7. •Planisprojectedtothemotorandpremotorcortex.
•Commandsaresenttomuscle→viacorticospinaland
corticobulbartracts.
•Feedbackinformationthatadjustsandsmoothens
movementrelayedtomotorcortexandspinocerebellum.
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8. Cortical Motor Areas
•Control voluntary movement
•Comprises of
1.Primary Motor Cortex
2.Premotor Area
3.Supplementary Motor Area
4.Posterior Parietal Cortex
5.Primary Somatosensory Area
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9. 1. Primary Motor Cortex
•M1, Brodmann area 4
•Located in precentral gyrus of frontal lobe.
•Begins laterally in the sylvian fissure, spreads superiorly
to the uppermost portion of the brain.
•Then dips deep into the longitudinal fissure.
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12. •Concernedwithexecutionofmovements.
•Generatessignalsthatcontroltheexecutionof
discrete,individualmovementsratherthanone
specificmuscle
•Topographical Representation –Motor Homunculus
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13. Motor Homunculus
•Figurativerepresentationofbodymapencodedin
primarymotorcortex.
•MappedbyPenfieldandRasmussen.
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17. •Each sideof the body is represented on the opposite
side in the brain.
•Inverted map→ feet at the top and face at the bottom
•Facial area is represented bilaterally.
•Area involved in speech and hand movements → large
representation in the cortex.
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18. •Axialmusculatureandproximalportionsoflimb
representedalongtheanterioredgeofprecentralgyrus.
•Distalpartoflimbalongtheposterioredge.
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20. Corticalrepresentationofeachbodypartisproportional
insizetotheskillwithwhichthepartisusedinfine
voluntarymovement.
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21. •Motorsystem"learnsbydoing"andperformance
improveswithrepetition→corticalplasticity.
•Mapsofmotorcortexarethereforenotimmutable.
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22. 2. Premotor Area
•Brodmann’sarea6
•Liesimmediatelyanteriortoprimarymotorcortex–
extendinginferiorlytoSylvianfissureandsuperiorlyto
longitudinalfissure
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23. DEPT. OF PHYSIOLOGY, GMCM 23
Containsasomatotopicmapthatisroughlysameasthat
ofprimarymotorcortex

24. •Complex“patterns”ofmovement.
•Concernedwithsettingpostureatthestartofaplanned
movementandgettingtheindividualtomove.
•Mostinvolvedincontrolofproximallimbmuscles
neededtoorientthebodyformovement.
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25. Premotor area sends signals
1.Eitherdirectlytoprimarymotorcortextoexcite
specificmuscles
2.Orbywayofbasalgangliaandthalamusbackto
primarymotorcortex
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26. Mirror Neurons?
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28. •Specialclassofneurons-mirrorneuronspresent.
•Transformsensoryrepresentationsofactsthatareheard
orseenintomotorrepresentationsoftheseacts.
•Importantforunderstandingtheactionsofotherpeople
andforlearningnewskillsbyimitation.
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29. Special areas in Premotor cortex
1.Broca’s area (Motor Speech Area) –related to speech
2.Voluntary eye movement field
1.For moving eyes toward different objects
2.Also controls eyelid movements such as blinking

30. 3.Headrotationarea
•Directstheheadtowarddifferentobjects
•Closelyassociatedwiththeeyemovementfield
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31. 4.Areaforhandskills
•Liesimmediatelyanteriortotheprimarymotor
cortexforthehandsandfingers
•Lesionscausehandmovementsbecomeun-
coordinatedandnon-purposeful-Motorapraxia
DEPT. OF PHYSIOLOGY, GMCM 31

32. 3. Supplementary motor area
•Situatedonandabovethesuperiorbankofcingulate
sulcus.
•Thisareaprojecttomotorcortex.

33. •Involvedinprogrammingmotorsequences–when
movementsperformedarecomplexandneedplanning.
•Lesionsproduceinabilitytoperformcomplexaction
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34. 4. Posterior Parietal cortex
•Two areas: area 5 and area 7
•Provide fibers to corticospinal and corticobulbar tracts
•Project to premotor cortex

35. •Neuronsinarea5areconcernedwithaimingthe
handstowardsanobjectandmanipulatingit.
•Neuronsinarea7areconcernedwithhandeye
coordination.
DEPT. OF PHYSIOLOGY, GMCM 35

36. 5. Primary somatosensory cortex
•Area 3, 1, 2
•Projects to premotor cortex.
•Lesion of somatosensory area affects learned sequence
of movements eg.Eating with knife and fork.
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37. Descending tracts or Motor pathways
1.Pyramidal tractorCorticospinal tractand
Corticobulbar orCorticonucleartract
2.Extra pyramidal pathways
•Reticulospinal, Vestibulospinal, Rubrospinal,
Tectospinal

38. Corticospinal tract or Pyramidal pathway
•Primary pathway for initiation of skilled voluntary
movements.
•Longest tract
•Becomes myelinatedin the first 2 yearsof life.

39. •Corticospinal tract + corticobulbar tract
•1 million fibers in each corticospinal tract
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40. A. Origin
1.30%from Primary motor cortex
2.30%from Premotor cortex and Supplementary motor area
3.40%from Somatosensoryarea posterior to central sulcus

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42. Cells of origin
•Giant pyramidal cells of Betz → 3%
•Small pyramidal cells → 97%
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43. Betz cells
•Betz in 1874 described the giant pyramidal cells in 5
th
layer of primary motor cortex.
•Only 3% of CST fibers arise from Betz cells -large cell,
velocity-70m/sec.

45. B. Course
Cerebral cortex-various areas
↓
Corona radiata
↓
Internal capsule –genu and anterior 2/3
rd
of
posterior limb (head region anteriorly, feet posteriorly)

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48. B. Course
Cerebral cortex-various areas
↓
Corona radiata
↓
Internal capsule –genu and anterior 2/3
rd
of
posterior limb (head region anteriorly, feet posteriorly)
↓
Midbrain–middle 3/5
th
of crus cerebri
(head medially, feet laterally)

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50. ↓
Pons(broken up to discrete bundles by pontine nuclei)
At the lower border collected into a compact bundle
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52. ↓
Pons(broken up to discrete bundles by pontine nuclei)
At the lower border collected into a compact bundle
↓
Medulla –seen as Pyramid
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54. Atthelowerborderofmedulla,
•80%crosstooppositeside–crossedPyramidaltractor
LateralCorticospinaltract
•20%uncrossed fibers –Anterior or Ventral Cortico-
spinal tract
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57. Lateral Corticospinal Tract
•80%ofpyramidalfiberscrosstooppositeside
•Descenddowninlateralfuniculusofspinalcord
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58. C.TerminationofLateralCST
•TerminatesatallspinalcordlevelsdirectlyonαMNs.
•LateralCST–makemonosynaptic direct
connectionstomotorneuronsonoppositeside
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59. •Controls distal limb muscles → concerned with fine
skilled movements
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60. Anterior Corticospinal Tract
•About20%fibersdonotcrossinmedulla
•Descenddowninanteriorfuniculusofspinalcord
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61. C.TerminationofAnteriorCST
•Mostoffiberscrossatthelevelofspinalcordwhere
theyterminate,butsomefibersremainuncrossed.
•AnteriorCST–connectwithinterneuronthatmake
connectionwithαmotorneurononbothsidesofbody
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62. •Controlsmusclesoftrunkandproximalmusclesof
limbs→concernedwithposturaladjustmentsand
grossmovements.
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64. Within the brainstem and spinal cord,
•Pathwaysandneuronsconcernedwithcontrolofaxial
muscles&proximallimbmusclesarelocatedmedially
orventrally.

65. Within the brainstem and spinal cord,
•Pathways&neuronsthatareconcernedwithcontrolof
musclesindistalportionsofthelimbsarelocated
laterally.

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67. C. Termination of CST
•Synapsewithαmotorneuroninanteriorhorndirectlyor
indirectlythroughinterneuron.
•Fewterminateonsensoryrelayneuronsindorsalhorn

68. •LateralCST–makemonosynapticdirectconnections
tomotorneuronsonoppositeside(esp.forskilled
movements)
•AnteriorCST–connectwithinterneuronthatmake
connectionwithαmotorneurononbothsidesofbody
DEPT. OF PHYSIOLOGY, GMCM 68

70. Corticobulbar or Corticonucleartracts
Throughoutthebrainstem,fibersaregivenofffrom
pyramidaltracttothenucleiofmotorcranialnervesofthe
oppositeside.

71. •Midbrain-3
rd
and 4
th
cranial nerve nuclei
•Pons -5
th
, 6
th
and 7
th
cranial nerve nuclei
•Medulla-9
th
,10
th
,11
th
and12
th
cranial nerve
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73. NEXT CLASS!
[email protected]
DEPT. OF PHYSIOLOGY, GMCM 73