Cerebellum 2010

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Cerebellum 2010

  1. 1. Cerebellar Control of Movements<br />
  2. 2. Organization of Cerebellum<br />
  3. 3. Functional organization of cerebellum<br />
  4. 4.
  5. 5. Input of Cerebellum<br />
  6. 6. Cerebellar Output<br />
  7. 7. Vestibulocerebellum<br />
  8. 8. Neocerebellum<br />
  9. 9. The spinocerebellum contains two somatotopic neural maps of the body<br />
  10. 10.
  11. 11.
  12. 12. Cerebellar Pathway<br />
  13. 13.
  14. 14. Cerebellum:Anatomy,connections,&functions<br />Dr.Rupjyoti Das<br />
  15. 15. The cerebellum (Latin: "little brain") is a region of the brain that plays an important role in the integration of sensory perception and motor control.<br />The cerebellum is located in the inferior posterior portion of the head (the hindrain), directly dorsal to the pons, and inferior to the occipital lobe &<br /> separated from cerebrum by tentoriumcerebelli.<br />Weight=150 gm<br />
  16. 16.
  17. 17. On axial & coronal planes,a midline portion,thevermis, and two lateral portions, the cerebellarhemispheres,can be recognized.<br />The vermis is developmetally older & receives mainly spinocerebellar afferents, whereas the hemispheres have more complex fibre connections.<br />
  18. 18. Schematic representation of the major anatomical subdivisions of the cerebellum.<br />
  19. 19. The cortex is convoluted into many folia. <br />Three major transverse divisions (lobes) are recognized—<br />The anterior lobe is most rostral, <br />posterior lobe and flocculo-nodular lobe more caudally. <br />These lobes are divided by the primary fissure and the posterolateral fissure, respectively. <br />Larselldescribed 10 lobules (subdivisions of the lobes) that can be recognized in all animals. Lobules I-V are within anterior lobe, lobules VI-IX are in posterior lobe and lobule X comprises the floccular-nodular lobe.<br />
  20. 20. Spinocerebellum<br />Pontocerebellum<br />Vestibulocerebellum<br />
  21. 21. Because of its large number of tiny granule cells, the cerebellum contains more than 50% of all neurons in the brain, but it only takes up 10% of total brain volume. <br />The cerebellum receives nearly 200 million input fibres.<br />
  22. 22. Anatomical division- :<br />the anterior lobe (rostral to the "primary fissure"), <br />the posterior lobe (dorsal to the "primary fissure") and <br />the flocculonodular lobe,<br />The first two can be further divided in a midline cerebellarvermisand lateral cerebellar hemispheres.<br />The cerebellum can be divided according to three different criteria: gross anatomical, phyologenetical, and functional:<br />
  23. 23. Classification by Phylogenetic and OntogenicDevelopment :<br />Archicerebellum<br />Paleocerebllum<br />Neocerebellum<br />Classification by Afferent Connection<br />Vestibulocerebellum<br />Spinocerebellum<br />Pontocerebellum<br />Classification by Efferent Connection<br />Vermis<br />Paravermal Region<br />Cerebellar Hemisphere<br />
  24. 24. From the phylogenetically oldest to the newest, the three parts are:<br />
  25. 25.
  26. 26.
  27. 27. During the early stages of embryonic development, the brain starts to form in three distinct segments:<br /> the prosencephalon, <br />mesencephalon, and <br />rhombencephalon. <br />The rhombencephalon is the most caudal (toward the tail) segment of the embryonic brain.<br />Development of cerebellum<br />
  28. 28. Archicerebellum<br /> (nodulus)<br />Archicerebellum<br /> (flocculus)<br />Paleocerebellum<br />Neocerebellum<br />
  29. 29. Along the embryonic rhombencephalic segment develop eight swellings, called rhombomeres. The cerebellum arises from two rhombomeres located in the alar plate of the neural tube, a structure that eventually forms the brain and spinal cord.<br />The specific rhombomeres from which the cerebellum forms are rhombomere 1 (Rh.1) caudally (near the tail) and the "isthmus" rostrally (near the front).<br />
  30. 30. The cerebellum is of archipalliarphylogenetic origin. The pallium is a term for gray matter that forms the cortex. The archipallium is the one of the most primitive brain regions. The circuits in the cerebellar cortex look similar across all classes of vertibrates, including fish, reptiles, birds, and mammals. <br />
  31. 31. Subdivision ofFlocculonodular Lobe<br />NodulusFlocculus<br /> Subdivision of Anterior Lobe<br />Vermis Hemisphere<br />Lingula<br />Central Lobule Ala Central Lobule<br />postcentral fissure<br />CulmenQuadriangular Lobule<br />Cerebellum-External configuration<br />
  32. 32. Subdivision of Posterior Lobe<br />Vermis Hemisphere<br />Declive Simple Lobule<br />postcentral fissure<br /> Folium Superior Semilunar Lobule<br />horizontal fissure<br /> Inferior Semilunar Lobule<br /> Tuber <br />Gracile Lobule<br />prepyramidal fissure<br /> Pyramid Biventral Lobule<br />secondary fissure<br /> Uvula Tonsil<br />
  33. 33.
  34. 34. Grey matter of cerebellum:<br />1.Cerebellar cortex.<br />2.Cerebellar nuclei<br />cytoarchitecture<br />
  35. 35.
  36. 36. The cerebellar cortex consists of three layers on a core of white matter.<br />1.Molecular layer<br />Consists mainly of neuropil and is the site of synapses.<br />Contains scanty neurons consisting of stellate and basket cells.<br />2.Purkinje cell (Piriform) layer<br />Single layer of neurons.<br />Consists of large (25 micrometer) pear-shaped neurons .<br />3.Granular cell layer<br />Very small(7 micrometer) granular neurons.<br />Very numerous – 3 to 7 million neurons per cubic mm.<br />4.White matter – forms the core of the foliae.<br />
  37. 37. 1.Outer stellate layer(In molecular layer)<br />2.Basket cells ( -do- )<br />3.Purkinje cells.<br />4.Granule cells. (In granule cell layer)<br />5.Golgi cells ( -do- )<br />Neurons of cerebellar cortex<br />
  38. 38.
  39. 39. The white matter of the cerebellum is made up of intrinsic,afferent & efferent fibres. <br />Incoming impulses to the cerebellum reach the dendrites and cell bodies of Purkinje cells.<br />The afferent fibres form the greater part of the cerebellar white matter and on entering the cerebellum,segregate into one of three fibre systems: the climbing,mossy or multilayered. <br />
  40. 40.
  41. 41. The climbing fibresare the terminal fibres of the olivocerebellar tracts & make multiple synaptic contacts with one Purkinje cell.<br />The mossy fibresystem includes all other cerebellar afferent tracts.In contrast to the climbing fibre system the mossy fibre system is diffuse,having multiple branches;so a single mossy fibre may stimulate thousands of Purkinje cells through the granule cell.<br />
  42. 42. The multilayered fibresystem includes afferents to the cerebellum from the hypothalamus,raphe nuclei & locus ceruleus & projects into the cerebellar cortex & deep cerebellar nuclei. <br />
  43. 43. In striking contrast to the 100,000-plus inputs from parallel fibers, each Purkinje cell receives input from exactly one climbing fiber; but this single fiber "climbs" the dendrites of the Purkinje cell, winding around them and making a large number of synapses as it goes.<br />
  44. 44. 8. parallel fiber 9. inferior oliva nucleus 0. d l nuclei<br /> 1. Purkinje cell <br /> 2. granule cell <br /> 3. basket cell <br /> 4. Golgi cell <br /> 5. stellate cell <br /> 6. climbing fiber <br /> 7. mossy fiber <br /> 8. parallel fiber <br /> 9. inferior olivary<br /> nucleus <br />10. deep cerebellar<br /> nuclei<br />
  45. 45.
  46. 46.
  47. 47. The Purkinje cells are central neurons (everything else converges on them) <br />They consist of= <br />A large dendritic tree in the molecular layer, which  is elaborately branched and  fan-shaped (branches are all in one plane) and has dendritic spines at the  sites of synapses.<br />A large cell body.<br /> An axon  which forms the efferent pathway from the cerebellum , and  sends collaterals in the granular layer.<br /> GABA is the main neurotransmitter.<br /> <br />
  48. 48. The Granule cells:<br />Very numerous: 3-7 million / mm3<br /> Very small (7mm), closely packed neurons.<br /> Heterochromatic nuclei, scanty cytoplasm.<br />Small dendritic tree in granule layer.<br />An unmyelinated axon.<br />Directed to molecular layer (centrifugal). <br /> *Splits in T-shape manner to form parallel fibre.<br /> Parallel fibers run longitudinally along folia<br /> Cross dendrites of many Purkinje cells.<br /> Have glutamate as neurotransmitter.<br /> <br />
  49. 49. Cerebellar Neurons are Stimulatory or Inhibitory to Purkinje Cells.<br /> Climbing fibres are strongly excitatory.<br />Mossy fibres stimulate granule cells.<br />Parallel fibres of granule cells stimulate several Purkinje cells simultaneously.<br />Basket cells strongly inhibit Purkinje cells.<br />Stellate cells inhibit Purkinje cell dendrites.<br />Golgi Type II cells inhibit directly the mossy fibre input.<br />
  50. 50. Main neurotransmitter= L-glutamate.<br />Afferents reaching Purkinje through<br /> (Mossy/Climbing fibres)<br /> :Excitatory.<br />Purkinje cells =GABAergic.<br />Golgi cells= -do-<br />Stellate cells = -do-<br />Basket cells = -do- <br />Neurochemistry<br />
  51. 51. Embedded within the white matter—which is known as the arbor vitae (Tree of Life) in the cerebellum due to its branched, treelike appearance—are four deep cerebellar nuclei:<br />From lateral to medial, they are the <br />dentate, <br />emboliform, <br />globose, and fastigial. <br />
  52. 52.
  53. 53. Dentate n. <br />Emboliform n.<br />Globose n.<br />Fastigial n.<br />
  54. 54. These nuclei receive inhibitory (GABAergic) inputs from Purkinje cells in the cerebellar cortex and <br />excitatory (glutamatergic) inputs from mossy fibre pathways. <br />Most output fibers of the cerebellum originate from these nuclei.<br />
  55. 55. The fastigial nucleus assists stance & gait & controls muscles only in the modes of sitting,standing & walking. <br />The nucleus interposed assists segmental reflexes & speeds the initiation of movement triggered by somatosensory cues.<br />The dentate nucleus assists in tasks requiring fine dextirity.<br />Each nucleus controls a diff.type of movement as follows:<br />
  56. 56. The cerebellum follows the trend of "threes", with three major input and output peduncles (fiber bundles). These are <br />the superior (brachium conjunctivum), <br />middle (brachium pontis), and <br />inferior (restiform body) cerebellar peduncles.<br />
  57. 57.
  58. 58.
  59. 59.
  60. 60. Cerebellar connections--<br />
  61. 61. Cont.<br />
  62. 62.
  63. 63. Afferent connection<br />
  64. 64. Main Connections of the Vestibulocerebellum<br />Vestibular<br /> Organ<br />Floculonodular<br /> Lobe<br />Vermis<br />VESTIBULAR NUCLEUS<br />vestibulospinal tract<br />MLF<br /> FASTIGIAL<br />NUCLEUS<br />lower motor neuron<br />ARCHICEREBELLUM<br />LMN<br />
  65. 65. Main Connections of the Paleocerebellum<br />NUCLEUS INTERPOSITUS<br />RED NUCLEUS<br />RED NUCLEUS<br />Rubro<br />spinal tract<br />ANTERIOR LOBE<br />PARAVERMAL ZONE<br />Inferior<br />Olivry<br />Nucleus<br />PALEOCEREBELLUM<br />Lower motor neuron<br />SPINAL CORD<br />spinocerebellar tract<br />
  66. 66. Main Connections of the Neocerebellum<br />CEREBRAL CORTEX<br />THALAMUS<br />DENTATE<br />NUCLEUS<br />Pontine<br />Nucleus<br />POSTERIOR <br />LOBE<br />CEREBELLAR HEMISPHERE<br />Pyramidal tract<br />NEOCEREBELLUM<br />Lower motor neuron<br />LMN<br />
  67. 67. Cerebellum and Automatic Motor Control<br />MOTOR CORTEX<br />CEREBELLUM<br />RED NUCLEUS<br />VESTIBULAR NUCLEUS<br />RETICULAR FORMATION<br />LOWER MOTOR NEURON<br />Proprioceptors<br />
  68. 68. Corticonuclear Connections<br />A zone ---------- fastigial nucleus<br /> medial vestibular nucleus<br />B zone ---------- lateral vestibular nucleus<br />C1, C3 zone --- emboliform nucleus<br />C2 ---------------- globose nucleus<br />D1 ---------------- parvocellular portion of dentate nucleus<br />D2 ---------------- magnocellular portion of dentate nucleus<br />Voogd originally described 4 zones, from medial to lateral--<br />
  69. 69. 1. vermis<br /> 2. paravermal region <br /> 3. cerebella hemisphere <br /> 4. nodulus<br /> 5. flocculus<br /> 6. fastigial nucleus<br /> 7. globose nucleus<br /> 8. emboliform nucleus<br /> 9. dentate nucleus<br />10. medial vestibular nucleus <br />11. lateral vestibular nucleus<br />
  70. 70. The inferior olivary nucleus or inferior olive comprises 3 major divisions – <br />the principal olive (PO),<br /> the dorsal accessory olive (DAO) and <br />the medial accessory olive (MAO). <br />Different divisions of the olive project to different cortical zones. The inferior olive is the only source of climbing fibre inputs to the cerebellum. Inputs from all other sources are as mossy fibres. <br />
  71. 71. Olivocerebellar Connections<br />Caudal portion of<br /> medial and dorsal accessory olivary nucleus<br /> ----------------- vermis of cerebellar cortex (A and B)<br />fastigial nucleus<br /> vestibular nucleus<br />Rostral portion of<br /> medial and dorsal accessory olivary nucleus<br /> ----------------- paravermal region (C1, C2, C3)<br /> nucleus interpositus<br />Principal Inferior Olivary Nucleus<br /> ----------------- cerebellar hemisphere (D1, D2)<br /> dentate nucleus<br />
  72. 72. Caudal portion<br />Rostral portion<br />Principal inferior olivary nucleus<br />medial and dorsal accessory olivary nucleus<br />
  73. 73. Vascular supply of the cerebellum:<br />The posterior inferior cerebellar artery (PICA): supplies-<br />Lat.medullarytegmentum,<br />inferior cerebellar peduncle<br />The ipsilat.portion of the inferior vermis &<br />the inferior surface of the cerebellar hemisphere.<br />The medial br. of the PICA supplies the medial cerebellum & the dorsolat. Medulla oblongata.<br />The lateral br.supplies the inferoposterolat. aspect of the cerebellum.<br />
  74. 74.
  75. 75. The ant.inf.cerebellar artery (AICA) supplies-<br />Ant.petrosal surface of the cerebellar hemisphere,<br />Flocculus,<br />Lower portion of the middle cerebellar peduncle &<br />Lat.pontomedullarytegmentum<br />
  76. 76. The superior cerebellar artery (SCA) supplies-<br />The upper surface of the cerebellar hemisphere,<br />Ipsilat.portion of the superior vermis,<br />Most of the dentate nucleus,<br />Upper portion of the MCP,SCP & lat.pontinetegmentum.<br />
  77. 77. Maintenance of Equilibrium<br />- balance, posture, eye movement <br />Coordination of half-automatic movement of<br /> walking and posture maintenace<br /> - posture, gait <br />Adjustment of Muscle Tone<br />Motor Leaning – Motor Skills<br />Cognitive Function<br />Cerebellum:functions<br />
  78. 78. BALANCE<br />
  79. 79. MOTOR SKILLS<br />
  80. 80. Archicerebelum<br />Floculonodular lobe- Vestibulocerebelum<br />Function: <br />Maintenance of equilibrium<br />Suppress Vestibulo Ocular Reflex<br />Muscle tone in relation to head posture<br />Animal ablation<br />Disorder of equilibrium<br />Positional nystagmus<br />Human: Meduloblastoma<br />Trunkal ataxia<br />Vestibular nystagmus (fast component towards the side of lesion)<br />Positional nystagmus does not fatigue<br />Vertigo<br />28 October 2010<br />
  81. 81. Palleo-cerebelum<br />Anterior lobe + Vermis<br />Afferent: <br />Spinocerebellar tract<br />Spino-> olivo->cerebellar<br />Spino -> reticulo -> cerebellar<br />Efferent<br />Festigio -> vestibulo -> spinal<br />Festigio -> Reticulo -> Spinal<br />Function<br />Tone control<br />Posture of axial muscle<br />Equilibrium and locomotion<br />Animal ablation<br />Increased lengthening and shortening<br />Increased tendon reflex<br />Exagerated postural reflex (positive supporting reflex)<br />Human<br />Alcoholic degeneration<br />Cerebellar degeneration<br />Gait ataxia<br />Rarely mild hypotonia, dysmetria and dysarthria<br />28 October 2010<br />
  82. 82. Neocerebelum<br />Ablation in Dog and Cat inconstant result<br />Monkey ablation<br />Hypotonia<br />Clumsiness of ipsilateral limb<br />Dentate nucleus ablation -> more enduring effect intension tremor<br />28 October 2010<br />
  83. 83. Cerebellar zones<br />Vermis zone: control posture, tone, locomotion, equilibrium<br />Vestibular connection project to festigial nucleus<br />Control position of the head in relation to trunk and extraocularmovments<br />Intermediate zone<br />Affrent- <br />proprioceptive from limb<br />Sensorimotor cortex<br />Collateral from corticospinal tract<br />Efferent globos and embodiform nucleus ->VL thalamus to motor cortex<br />Function: Regulation of movment via sensory feedback from the corticospinal muscle<br />Control velocity, force, pattern of movement<br />28 October 2010<br />
  84. 84. Cerebellar zones: Lateral<br />Afferent: motor and sensory association cortex<br />Efferent: Dantate -> thalamus -> motor cortex (open loop)<br />Function: Programing of movement before initiation<br />Animal: coordination of ipsilateralmovment<br />Human: Hypotonia- flabby muscle, abnormal posture (slopping of shoulder) increased excursion of outstretched hand tapping. Hyperflexibility of joint, pendular reflex knee<br />Cerebellum control separately the activity of alpha and gamma motor neuron<br />Reduced fusimotor activity from abnormal long loop reflex through precentral cortex<br />28 October 2010<br />
  85. 85. Cerebellar dysfunction<br />Ataxia: Limb, gait and speech<br />Speech: Scanning<br />Tremor: Postural, intention, limb, trunk and head<br />Tone: Hypotonia -> Hyperextensibility, pendular knee jerk, rebound phenomenon<br />Voluntary movement: Dysmetria, dysynergia, disdidokokinesia<br />Gait: ataxic, truncal ataxia<br />Head tilt<br />Postural abnormality: due to unequal hypotonia of truncal muscle -> scoliosis, elevation or depression of shoulder, pelvic tilt<br />28 October 2010<br />
  86. 86. Voluntary movement abnormality<br />Gorden Holms : Rate, range and force <br />Dyssynergia: Disruption of the normal smooth control of movement provided by gradual contraction of synergic muscle and relaxation of their antagonist<br />Voluntary movement- longer to start and longer to stop<br />Prolongation of interval between the command and triphasic agonist- antagonist and motor sequence<br />Agonist burst may be too long or short or continue into the antagonist burst -> dysmetria and dysenergia<br />Rebound phenomenon (abnormal check reflex)<br />Dysdiadokokinesia<br />Decomposition of movement<br />Scanning speech<br />Cogwheel eye moevment<br />28 October 2010<br />
  87. 87. Voluntary movement abnormality<br />Dysmetria<br />Inability of the sensorimotor apparatus to measure distance in the course of movement<br />Hypometria and hypermetria of the limb and eye<br />Tremor : Postural and intention<br />Ataxia of gait: falling towards the side of lesion<br />Nystagmus: <br />Gaze paretic (evoked) deviation<br />Downbeat<br />Rebound<br />Sustained horizontal<br />Opsoclonus<br />Skew deviation<br />Weakness, faitibability and loss of associted movement <br />28 October 2010<br />

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