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Lecture on PHYSIOLOGY of Cerebellum by Dr. Roomi

Jun 04, 2018

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    PHYSIOLOGY

    of

    CEREBELLUM

    By

    Dr. Mudassar Ali Roomi (MBBS, M.Phil.)Assistant Professor Physiology

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    CEREBELLUM

    Largest part of hindbrain.

    LOCATION: Posterior

    cranial fossa behind

    pons & medulla.

    ANATOMY: Covered

    above by meninges

    (Tentorium Cerebelli). Has 2 hemispheres

    joined by Vermis.

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    LOBES:three1) anterior lobe

    2) posterior / middle lobe

    3) flocculo nodular lobe

    FISSURES:two1) Primary fissure (v

    shaped). Part ofcerebellum above thisfissure is anterior lobe.

    2) Uvulo-nodular fissure(separates posterior lobefrom flocculo nodularlobe).

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    FUNCTIONAL ZONES OF CEREBELLUM

    Each cerebellar

    hemisphere has 2

    functional zones,

    intermediate zone&lateral zone.

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    Topographical representation

    Axial parts of body

    represented in Vermis.

    Limbs & facial region

    Intermediate zone.

    http://www.google.com/url?sa=i&rct=j&q=WHITE+MATTER+OF+CEREBELLUM&source=images&cd=&cad=rja&docid=dNe-NEvJjMEM6M&tbnid=-yPgU5SbRG7KhM:&ved=0CAUQjRw&url=http://antranik.org/central-nervous-system-intro-to-brain-and-ventricles-medulla-oblongata-pons-mid-brain-and-cerebellum/&ei=Zy9QUZjlKsnCPOb-gYAP&bvm=bv.44158598,d.ZGU&psig=AFQjCNE2K78yIMy44Sp20Rw7-k-cOy6m1Q&ust=1364295884846382
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    Cerebellum has: 1) cortex cerebellar (grey

    matter on periphery)

    2) white matter core (having

    deep cerebellar nuclei, 4 oneach side, from lateral tomedial side:

    DENTATE, EMBOLIFORM,GLOBoSE & FESTIGEAL.(Lateral medial)

    DEGF! (dont eat greasy food) EMBOLIFORM + GLOBoSE =

    NUCLEUS INTERPOSITUS.

    http://www.google.com/url?sa=i&rct=j&q=WHITE+MATTER+OF+CEREBELLUM&source=images&cd=&cad=rja&docid=dNe-NEvJjMEM6M&tbnid=-yPgU5SbRG7KhM:&ved=0CAUQjRw&url=http://antranik.org/central-nervous-system-intro-to-brain-and-ventricles-medulla-oblongata-pons-mid-brain-and-cerebellum/&ei=Zy9QUZjlKsnCPOb-gYAP&bvm=bv.44158598,d.ZGU&psig=AFQjCNE2K78yIMy44Sp20Rw7-k-cOy6m1Q&ust=1364295884846382http://www.google.com/url?sa=i&rct=j&q=cerebellar%20nuclei&source=images&cd=&cad=rja&docid=Mi9L9-tXiLYbOM&tbnid=5t_hdYTH06dRyM:&ved=0CAUQjRw&url=http://quizlet.com/5348748/neuro-unit-4-l2-flash-cards/&ei=5y1QUfeZDonbPPvEgbgJ&bvm=bv.44158598,d.ZGU&psig=AFQjCNFhGJfY-4B5cFH8nNb6MuMH_3aYLw&ust=1364295339558837
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    CEREBELLAR CORTEX:

    3 LAYERS:

    Outermostmolecular

    layer (STELLATE CELLS,

    BASKET CELLS).

    2ndlayerpurkinje cells

    layer (Single cell layer of

    Flask shaped cells).

    3

    rd

    later

    granular layer

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    INTRINSIC FIBERS:

    Pass between cerebellar

    cortex & vermis.

    Also pass from 1

    cerebellar hemisphereto other.

    They remain in the

    cerebellum.

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    AFFERENT FIBERS:

    2 TYPES:

    CLIMBING FIBERS(come

    from inferior olivary

    nucleus)

    MOSSY FIBERS(all the

    other afferent fibers

    except the climbing are

    called Mossy fibers).

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    EFFERENT FIBERS:

    Start as axons of Purkinje cells.

    Most of these axons synapseonto deep nuclear cells.

    From deep nuclear cells,efferent fibers arisego todifferent parts of CNS .

    Only few purkinje fibers

    bypass deep nuclear cellsgo to vestibular nuclei(theseare from vermis & flocculo-nodular lobe).

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    neuronal circuit in the cerebellum

    There is a neuronal circuit incerebellum.

    Millions of such functional units.

    Each functional unitconsist of apurkinje cell & a deep nuclear

    cell.

    Climbing fibersgive collaterals,which synapse with deep nuclearcells.

    collaterals from climbing fibers

    excite deep nuclear cells.

    Climbing fiberspass tomolecular layersynapse withdendrites of purkinje cells.

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    neuronal circuit in the cerebellum

    (cont) Mossy fiberscollateralssynapse with deepnuclear cells.

    Mossy fibersgranular

    layersynapse withdendrites of granule cell.

    1 climbing fibercan synapsewithabout 10 purkinjecells.

    1 mossy fibercan synapsewith 100s of granule cells.

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    neuronal circuit in the cerebellum

    (cont)

    Excitatory cells:

    deep nuclear cells

    Granule cells

    Inhibitory cells:

    Purkinje cells

    Basket cells

    Golgi II cells

    Stellate cells

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    http://www.google.com/url?sa=i&rct=j&q=INFERIOR+CEREBELLAR+PEDUNCLE+CONNECTIONS:&source=images&cd=&cad=rja&docid=0EbjyPcQ8qg3NM&tbnid=fr903MHbwVgL4M:&ved=0CAUQjRw&url=http://www.studyblue.com/notes/note/n/cerebellum/deck/841584&ei=3DFQUeirM4iHPau7gOgB&bvm=bv.44158598,d.ZGU&psig=AFQjCNENcrDPs9s0WT73fqnVFyRDvMnOpQ&ust=1364296506951151
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    http://www.google.com/url?sa=i&rct=j&q=INFERIOR+CEREBELLAR+PEDUNCLE+CONNECTIONS:&source=images&cd=&cad=rja&docid=0EbjyPcQ8qg3NM&tbnid=fr903MHbwVgL4M:&ved=0CAUQjRw&url=http://www.studyblue.com/notes/note/n/cerebellum/deck/841584&ei=3DFQUeirM4iHPau7gOgB&bvm=bv.44158598,d.ZGU&psig=AFQjCNENcrDPs9s0WT73fqnVFyRDvMnOpQ&ust=1364296506951151
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    CONNECTIONS OF CEREBELLUM THROUGH 3

    PEDUNCLES:

    AFFERENT

    EFFERENT

    Superior peduncle

    midbrainMiddle peduncle

    pons

    Inferior peduncle

    medulla

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    INFERIOR CEREBELLAR PEDUNCLE

    CONNECTIONS:

    AFFERENTS: Posterior spino-cerebellar

    tract.

    Vestibulo-cerebellar fibers

    (from vestibular nuclei).

    Reticulo cerebellar (fromreticular formation).

    Olivo-cerebellar (from inferior

    olivary nucleus).

    EFFERENTS: Cerebello-vestibular

    Cerebello-reticular

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    http://www.google.com/url?sa=i&rct=j&q=+CEREBELLAR+CONNECTIONS:&source=images&cd=&cad=rja&docid=Fy5hSEfHfIJMIM&tbnid=5VHt5uDK3v43gM:&ved=0CAUQjRw&url=http://www.dizziness-and-balance.com/anatomy/cerebellum.htm&ei=OTJQUZ2qPMjtOurDgYAC&bvm=bv.44158598,d.ZGU&psig=AFQjCNGCKaJG1mGeMT5fNUyqZD5MCiYoCg&ust=1364296619213544
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    MIDDLE PEDUNCLE:

    Mainly AFFERENTS (Ponto-cerebellar fibers).

    These fibers arise frompontine nuclei & crossover to opposite sidemiddle cerebellarpeduncle.

    These fibers are part ofcortico-ponto-cerebellar pathway.

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    SUPERIOR PEDUNCLE:

    AFFERENTS:

    ventral spino-cerebellar

    tract.

    Rubro-cerebellar tract

    (from red nucleus).

    Tecto-cerebellar (fromtectum of midbrain).

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    EFFERENTS:

    To Red nucleus,thento thalamic nuclei

    then to Cerebralcortex.

    To thalamus

    to basal ganglia.

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    CEREBELLUM HAS RECIPROCAL

    CONNECTIONS with

    1) CEREBRAL CORTEX

    2) RETICULAR FORMATION

    3) VESTIBULAR NUCLEI 4) RED NUCLEUS

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    BASIC FUNCTION OF CEREBELLUM:

    To control timing of:

    1. turn-on signals to agonists & turn-off signals to

    antagonists at the onset of a movement &

    2. turn-off signal to agonists & turn-on signals to

    antagonists at the end of a movement.

    Basic disturbance in cerebellar diseaseATAXIA /

    INCOORDINATION OF MOVEMENT.

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    FUNCTIONS OF CEREBELLUM:

    Functionally divided into 3 parts:

    1) lateral zone

    2) intermediate zone

    3) flocculo-nodular lobe & vermis.

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    LATERAL ZONE: FUNCTION

    No body representation.

    Also called cerebro-cerebellum(extensiveconnections with cerebral

    cortex). Program & plan movement.

    Plans, sequence & timing ofeach component ofmovement.

    Smooth progress ofmovement, e.g, eating thecurry & bread (breadcurrymouth).

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    *cerebellum does notINITIATE movement BUTCOORDINATES it.

    In cerebellar diseaselossof smooth progression ofmovements.

    Extra motor predictivefunction.

    Helps to access timing ofmovement.

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    INTERMEDIATE ZONE: FUNCTION

    Also called spino-cerebellum, due toconnection with spinal cord.

    Face & limbs are

    represented. Coordination of movements

    (distal part of limbs). Acts as a comparator.

    Compares intended plan ofmovement with actuallyperformed movement.

    In case of discrepancy,corrective signals are sent.

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    Cerebellum gets intendedplan of movement frommotor cortex& also fromred nucleus.

    shows cerebral &cerebellar controlofvoluntary movementsinvolving especially

    intermediate zone& itsassociated nucleusinterpositus.

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    It recieves informationactually performedmovements fromPROPRIOCEPTORS

    through spino-cerebellar tracts.

    Compared & correctedvia signals throughthalamic nuclei tomotor cortex.

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    Also controls: rate, range & direction of

    movement.

    Damping function.

    Prevents pendular movements & tremors

    (pendular knee jerk in case of disease)

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    Also controls very rapid movements like typing

    (ballistic movements).

    Also controls very rapid eye movement

    (reading & when a person in a moving vehicle,

    fixate the outside scene).

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    FUNCTION OF FLOCCOLONODULAR LOBE &

    VERMIS:

    Also called vestibulo-cerebellum due to connectionwith vestibular nuclei.

    Controls posture &equilibrium.

    Also concerned with motion

    sickness. Controls stretch reflex &

    muscle tone. Normal influence is facilitatory

    on stretch reflex & muscletone.

    From here purkinje nervefibersvest nuclei (bypassdeep nuclear cells)

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    CEREBELLAR DISEASE:

    Involvement of cerebellar cortex & 1 or more

    of deep cerebellar nuclei.

    *No muscle paralysis & no sensory loss occurs.

    (MCQ)

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    FEATURES OF CEREBELLAR DISEASE::

    1) ATAXIA: Incoordinate movements due to defect in control of

    RANGE, DIRECTION, RATE & TIMING of movement.

    Asynergia (no synergism between agonists &

    antagonists; normal synergism = when agonistscontract, antagonists relax).

    2) DYSMETRIA & PAST POINTING: Inability to control range or extent of movement.

    Dysmetriaalso manifest as past pointing. When patient tries to touch an objecthand

    overshoots (past pointing).

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    3) ADIADOCOKINESIA /

    DYSDIADOCOKINESIA:

    Inability to perform RAPID, ALTERNATE, OPPOSITE

    movement (rapid supination & pronation of arm).

    4) DRUNKEN GATE / STAGGERING GATE:

    Patient walks on a broad base.

    SPECIFIC POSTURE: Head is rotated & flexedtowards the side of lesion.

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    5) SLURRED SPEECH: Due to dysarthria ( disordered articulation).

    Incoordination of muscles of articulation.

    Some words or syllables are spoken loud & others are

    spoken in weak tone. Some are held for long period & some are spoken

    short.

    6) INTENTION TREMORS / ACTION TREMORS:

    Absent at rest. Appear when patient performs some voluntary action.

    Example of drinking water from a cup.

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    7) REBOUND PHENOMENON:

    Patient cannot stop a movement abruptly.

    Example of flexion of elbowmay hit his face.

    8) DECOMPOSITION OF MOVEMENTS: Patient is not able to perform actions involving

    simultaneous movement at more than 1 joint.

    Movements are broken into components.

    Loss of smooth progression of 1 movement toother.

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    9) NYSTAGMUS: Rhythmic rapid movement of eyeballs when eyes are

    focused on 1 side.

    Cerebellum has a damping function, which is

    disturbed. 10) PENDULAR KNEE JERK:

    Due to loss of damping function of intermediate zoneof cerebellum.

    11) HYPOTONIA: Due to loss of excitatory action of cerebellum on

    stretch reflex & muscle tone.