physiology of Cerebellum lec foe 2nd year by dr sadia uploaded by zaigham

CEREBELLUMCEREBELLUMLargest part of hind brain.Largest part of hind brain.

LOCATIONLOCATION: Posterior cranial fossa behind : Posterior cranial fossa behind pons & medulla.pons & medulla.

ANATOMY:ANATOMY: Covered above by meninges Covered above by meninges (Tentorium Cerebelli).(Tentorium Cerebelli).

Has 2 hemispheres joined by Vermis.Has 2 hemispheres joined by Vermis.

LOBES:LOBES: 3 3 1) anterior lobe1) anterior lobe 2) posterior / middle lobe2) posterior / middle lobe 3) flocculo nodular lobe3) flocculo nodular lobe FISSURES:FISSURES: 2 2 1) Primary fissure (v shaped). Part of 1) Primary fissure (v shaped). Part of

cerebellum above this fissure is anterior lobe.cerebellum above this fissure is anterior lobe. 2) Uvulo-nodular fissure (separates posterior 2) Uvulo-nodular fissure (separates posterior

lobe from flocculo nodular lobe)lobe from flocculo nodular lobe)

Anterior lobe + (pyramid + uvula of vermis) = Anterior lobe + (pyramid + uvula of vermis) = Paleo-cerebellum.Paleo-cerebellum.

Posterior lobe – (pyramid + uvula of vermis) = Posterior lobe – (pyramid + uvula of vermis) = Neo-cerebellum.Neo-cerebellum. (largest portion of cerebellum) (largest portion of cerebellum)

Flocculonodular lobe = Flocculonodular lobe = Archi-cerebellumArchi-cerebellum Developmentally, paleo Developmentally, paleo old part, old part, Neo Neo new, new, Archi Archi oldest. oldest.

Topographical representation:Topographical representation: Vermis & Vermis & Intermediate zone of cerebellar hemisphere.Intermediate zone of cerebellar hemisphere.

Each cerebellar hemisphere has 2 zones, Each cerebellar hemisphere has 2 zones, intermediate zoneintermediate zone & & lateral zonelateral zone..

Axial parts of body Axial parts of body represented in represented in Vermis.Vermis.

Limbs & facial region Limbs & facial region Intermediate zone. Intermediate zone.

AFFERENTS TO TOPOGRAPHICAL AFFERENTS TO TOPOGRAPHICAL REPRESENTATION:REPRESENTATION:

Corresponding areas of motor cortex.Corresponding areas of motor cortex. Corresponding parts of the body & Corresponding parts of the body & Brain stemBrain stem EFFERENTS:EFFERENTS: Cerebral cortexCerebral cortex Red nucleusRed nucleus Reticular formationReticular formation

VERMIS: 10 Primary lobules.VERMIS: 10 Primary lobules.

II LINGULALINGULA

IIII CENTRAL LOBULECENTRAL LOBULE

IIIIII CENTRAL LOBULECENTRAL LOBULE

IVIV CULMENCULMEN

VV DECLIVEDECLIVE

VIVI SIMPLE LOBULESIMPLE LOBULE

VIIVII FOLIUM TUBER.FOLIUM TUBER.

VIIIVIII PYRAMIDPYRAMID

IXIX UVULAUVULA

XX NODULENODULE

Cerebellum has:Cerebellum has:

1) cortex cerebellar (grey matter on periphery) &1) cortex cerebellar (grey matter on periphery) & 2) white matter core (having deep cerebellar nuclei, 2) white matter core (having deep cerebellar nuclei,

4 on each side, from lateral to medial side:4 on each side, from lateral to medial side: DENTATE,DENTATE, EMBOLIFORM, EMBOLIFORM, GLOBASE GLOBASE FESTIGEAL. (Lateral FESTIGEAL. (Lateral medial) medial) DEGFDEGF! (don’t eat greasy food)! (don’t eat greasy food) EMBOLIFORM + GLOBASE = NUCLEUS EMBOLIFORM + GLOBASE = NUCLEUS

INTERPOSITUSINTERPOSITUS..

MOTOR OUTPUT FROM MOTOR OUTPUT FROM CEREBELLUM:CEREBELLUM:

Axons of neurons in deep cerebellar nuclei Axons of neurons in deep cerebellar nuclei motor output. motor output.

From dentate + interpositus From dentate + interpositus leave via leave via SUPERIOR CEREBELLAR PEDUNCLE.SUPERIOR CEREBELLAR PEDUNCLE.

From fastigial nucleus From fastigial nucleus leave via leave via

INFERIOR CEREBELLAR PEDUNCLE.INFERIOR CEREBELLAR PEDUNCLE.

F G E D( N.I)

SUPERIOR CEREBELLAR PEDUNCLE

INFERIOR CEREBELLAR PEDUNCLE

CEREBELLAR CORTEX:CEREBELLAR CORTEX:

3 LAYERS:3 LAYERS: Outermost Outermost molecular layer molecular layer 22ndnd layer layer purkinje cells layer purkinje cells layer 33rdrd layer layer granular layer granular layer

PURKINJE CELL

AXONS

DENDRITES

MOLECULAR LAYER:MOLECULAR LAYER:

STELLATE CELLSSTELLATE CELLS BASKET CELLSBASKET CELLS Large no. of dendrites & nerve fibers Large no. of dendrites & nerve fibers

from deeper layers.from deeper layers.

PURKINJE CELL LAYER:PURKINJE CELL LAYER:

Single layer.Single layer. Flask shaped cells.Flask shaped cells. From top of cells arise dendrites From top of cells arise dendrites 1 1°°, 2, 2° (° (without without

dendritic spines, i.e., smooth)dendritic spines, i.e., smooth) & 3& 3°° branches (with dendrite spines). branches (with dendrite spines).

From base of cells From base of cells axons axons white matter white matter acquires acquires myelin sheath.myelin sheath.

Most nerve fibers from purkinje cells Most nerve fibers from purkinje cells synapse onto synapse onto deep nuclear cells.deep nuclear cells.

Only few fibers bypass deep nuclear cells Only few fibers bypass deep nuclear cells go to go to vestibular nuclei.vestibular nuclei.

GRANULAR LAYER:GRANULAR LAYER:

Granule cells havingGranule cells having Multiple dendrites Multiple dendrites synapse with synapse with

incoming Mossy fibers.incoming Mossy fibers. Their axons Their axons pass into pass into molecular molecular

layer layer end into a T termination. end into a T termination. These fibers also synapse with golgi These fibers also synapse with golgi

cells, basket cells & stallate cells.cells, basket cells & stallate cells.

WHITE MATTER OF WHITE MATTER OF CEREBELLUM:CEREBELLUM:

3 TYPES OF FIBERS:3 TYPES OF FIBERS: INTRINSICINTRINSIC FIBERS FIBERS AFFERENTAFFERENT FIBERS FIBERS EFFERENTEFFERENT FIBERS FIBERS

INTRINSIC FIBERS:INTRINSIC FIBERS:

Pass between cerebellar cortex & vermis.Pass between cerebellar cortex & vermis. Also pass from 1 cerebellar hemisphere Also pass from 1 cerebellar hemisphere

to other.to other. They remain in the cerebellumThey remain in the cerebellum..

AFFERENT FIBERS:AFFERENT FIBERS:

2 TYPES:2 TYPES: CLIMBING FIBERSCLIMBING FIBERS (come from inferior (come from inferior

olivary nucleus)olivary nucleus) MOSSY FIBERSMOSSY FIBERS (all the other afferent (all the other afferent

fibers except the climbing are called fibers except the climbing are called Mossy fibers).Mossy fibers).

EFFERENT FIBERS:EFFERENT FIBERS:

Start as axons of purkinje cells.Start as axons of purkinje cells. Most of these axons synapse onto deep Most of these axons synapse onto deep

nuclear cells.nuclear cells. From deep nuclear cells, efferent fibers arise From deep nuclear cells, efferent fibers arise

go to different parts of nervous system. go to different parts of nervous system. Only few purkinje fibers bypass deep nuclear Only few purkinje fibers bypass deep nuclear

cells cells go to go to vestibular nucleivestibular nuclei (these are from (these are from vermis & flocculo-nodular lobevermis & flocculo-nodular lobe).).

There is a neuronal circuit in cerebellum.There is a neuronal circuit in cerebellum. Millions of functional units.Millions of functional units. Each Each functional unitfunctional unit consist of a consist of a purkinje cell & purkinje cell &

a deep nuclear cell.a deep nuclear cell. Climbing fibersClimbing fibers give collaterals, which synapse give collaterals, which synapse

with with deep nuclear cellsdeep nuclear cells.. collaterals from climbing fibers collaterals from climbing fibers excite excite deep deep

nuclear cells.nuclear cells. Climbing fibersClimbing fibers pass to molecular layer pass to molecular layer

synapse with dendrites of synapse with dendrites of purkinje cellspurkinje cells..

Mossy fibersMossy fibers collaterals collaterals synapse synapse with deep nuclear cells.with deep nuclear cells.

Mossy fibersMossy fibers granular layer granular layer synapse with dendrites of granule cell.synapse with dendrites of granule cell.

1 1 climbing fiberclimbing fiber can synapse with can synapse with about 10 purkinje cells.about 10 purkinje cells.

1 1 mossy fibermossy fiber can synapse with 100’s of can synapse with 100’s of granule cells.granule cells.

Excitatory: Excitatory: deep nuclear cellsdeep nuclear cells Granule cellsGranule cells Inhibitory:Inhibitory: Purkinje cellsPurkinje cells Basket cellsBasket cells Golgi cellsGolgi cells Stellate cellsStellate cells

When deep nuclear cells are to be When deep nuclear cells are to be excited, its through COLLATERALS from excited, its through COLLATERALS from climbing & mossy fibers.climbing & mossy fibers.

When inhibited, its through purkinje cells.When inhibited, its through purkinje cells. Purkinje cells & deep nuclear cells Purkinje cells & deep nuclear cells

discharge continuously (50-100 discharge continuously (50-100 impulses/sec). This is the neuronal circuit impulses/sec). This is the neuronal circuit in the cerebellum.in the cerebellum.

BASIC FUNCTION OF BASIC FUNCTION OF CEREBELLUM:CEREBELLUM:

To control timing of turn-on signals to agonists To control timing of turn-on signals to agonists & turn-off signals to antagonists at the onset of & turn-off signals to antagonists at the onset of a movement & thena movement & then

To control timing of turn-off signal to agonists & To control timing of turn-off signal to agonists & turn-on signals to antagonists at the end of a turn-on signals to antagonists at the end of a movement.movement.

Basic disturbance in cerebellar disease Basic disturbance in cerebellar disease ATAXIA / INCOORDINATION OF ATAXIA / INCOORDINATION OF MOVEMENT.MOVEMENT.

CONNECTIONS OF CONNECTIONS OF CEREBELLUM THROUGH 3 CEREBELLUM THROUGH 3 PEDUNCLES:PEDUNCLES:

AFFERENTAFFERENT EFFERENTEFFERENT

Superior peduncleSuperior peduncle midbrain midbrain

Middle peduncleMiddle peduncle pons pons

Inferior peduncleInferior peduncle medulla medulla

INFERIOR CEREBELLAR INFERIOR CEREBELLAR PEDUNCLE CONNECTIONS:PEDUNCLE CONNECTIONS:

AFFERENTS:AFFERENTS: Posterior spino-cerebellar tract.Posterior spino-cerebellar tract. Cuneo-cerebellar tract (from cuneate nucleus). Cuneo-cerebellar tract (from cuneate nucleus).

Also called posterior external arcuate fibers.Also called posterior external arcuate fibers. Vestibulo-cerebellar fibers (from vestibular Vestibulo-cerebellar fibers (from vestibular

nuclei).nuclei). Reticulo cerebellar (from reticular formation).Reticulo cerebellar (from reticular formation). Olivo-cerebellar (from inferior olivary nucleus).Olivo-cerebellar (from inferior olivary nucleus).

EFFERENTS:EFFERENTS: Cerebello-vestibularCerebello-vestibular Cerebello-reticularCerebello-reticular

MIDDLE PEDUNCLE:MIDDLE PEDUNCLE:

Mainly AFFERENTS (Ponto-cerebellar Mainly AFFERENTS (Ponto-cerebellar fibers).fibers).

These fibers arise from pontine nuclei & These fibers arise from pontine nuclei & cross over to opposite side cross over to opposite side middle middle cerebellar peduncle.cerebellar peduncle.

These fibers are part of cortico-ponto-These fibers are part of cortico-ponto-cerebellar pathway.cerebellar pathway.

SUPERIOR PEDUNCLE:SUPERIOR PEDUNCLE:

AFFERENTS:AFFERENTS: Anterior spino-cerebellar tract.Anterior spino-cerebellar tract. Rubro-cerebellar tract (from red nucleus).Rubro-cerebellar tract (from red nucleus). Tecto-cerebellar (from tectum of Tecto-cerebellar (from tectum of

midbrain).midbrain).

EFFERENTS:EFFERENTS: To Red nucleus, thenTo Red nucleus, then To thalamic nuclei, then toTo thalamic nuclei, then to Cerebral cortex.Cerebral cortex. Other fibers Other fibers go directly go directly ventro- ventro-

lateral & ventro anterior thalamic nuclei lateral & ventro anterior thalamic nuclei cerebral cortex. cerebral cortex.

Some Some basal ganglia. basal ganglia.

CEREBELLUM HAS CEREBELLUM HAS RECIPROCAL CONNECTIONS RECIPROCAL CONNECTIONS WITH ???? (M.C.Q)WITH ???? (M.C.Q)

1) CEREBRAL CORTEX1) CEREBRAL CORTEX 2) RETICULAR FORMATION2) RETICULAR FORMATION 3) VESTIBULAR NUCLEI3) VESTIBULAR NUCLEI 4) RED NUCLEUS4) RED NUCLEUS

AFFERENTS AFFERENTS EFFERENTS EFFERENTS

FUNCTIONS OF FUNCTIONS OF CEREBELLUM:CEREBELLUM:

Functionally divided into 3 parts:Functionally divided into 3 parts: 1) lateral zone1) lateral zone 2) intermediate zone2) intermediate zone 3) flocculo-nodular lobe & vermis.3) flocculo-nodular lobe & vermis.

LATERAL ZONE: LATERAL ZONE: FUNCTIONFUNCTION

No body representation.No body representation. Also called cerebro-cerebellum (extensive Also called cerebro-cerebellum (extensive

connections with cerebral cortex).connections with cerebral cortex). Program & plan movement.Program & plan movement. Plans sequence & timing of each component of Plans sequence & timing of each component of

movement.movement. Smooth progress of movement, e-g, eating the Smooth progress of movement, e-g, eating the

curry & bread (breadcurry & bread (bread curry curry mouth). mouth).

*cerebellum does not INITIATE *cerebellum does not INITIATE movement BUT COORDINATES it.movement BUT COORDINATES it.

In cerebellar disease In cerebellar disease loss of smooth loss of smooth progression of movements.progression of movements.

Extra motor predictive function.Extra motor predictive function. Helps to access timing of movement.Helps to access timing of movement.

INTERMEDIATE ZONE: INTERMEDIATE ZONE: FUNCTIONFUNCTION

Also called spino-cerebellum, due to Also called spino-cerebellum, due to connection with spinal cord.connection with spinal cord.

Face & limbs are represented.Face & limbs are represented. Coordination of movements (distal part of Coordination of movements (distal part of

limbs).limbs). Acts as a comparator.Acts as a comparator. Compares intended plan of movement with Compares intended plan of movement with

actually performed movement.actually performed movement. In case of discrepancy, corrective signals are In case of discrepancy, corrective signals are

sent.sent.

Cerebellum gets intended plan of Cerebellum gets intended plan of movement from movement from motor cortexmotor cortex & also from & also from red nucleusred nucleus..

Fig shows Fig shows cerebral & cerebellar controlcerebral & cerebellar control of of voluntary movements involving especially voluntary movements involving especially intermediate zoneintermediate zone & its associated & its associated nucleus interpositusnucleus interpositus..

It recieves information actually performed It recieves information actually performed movements from PROPRIOCEPTORS movements from PROPRIOCEPTORS through spino-cerebellar tracts.through spino-cerebellar tracts.

Compared & corrected via signals Compared & corrected via signals through red nucleus & thalamic nuclei to through red nucleus & thalamic nuclei to motor cortex.motor cortex.

Also controls: rate, range & direction of Also controls: rate, range & direction of movement.movement.

Damping function.Damping function. Prevents pendular movements & tremors Prevents pendular movements & tremors

(pendular knee jerk in case of disease)(pendular knee jerk in case of disease)

Also controls very rapid movements like Also controls very rapid movements like typing (ballistic movements).typing (ballistic movements).

Also controls very rapid eye movement Also controls very rapid eye movement (reading & when a person in a moving (reading & when a person in a moving vehicle, fixate the outside scene).vehicle, fixate the outside scene).

FUNCTION OF FUNCTION OF FLOCCOLONODULAR LOBE & FLOCCOLONODULAR LOBE & VERMIS:VERMIS:

Controls posture & equilibrium.Controls posture & equilibrium. Also concerned with motion sickness.Also concerned with motion sickness. Controls stretch reflex & muscle tone.Controls stretch reflex & muscle tone. Normal influence is facilitatory on stretch reflex Normal influence is facilitatory on stretch reflex

& muscle tone.& muscle tone. From here purkinje nerve fibers From here purkinje nerve fibers vest nuclei vest nuclei

(bypass deep nuclear cells)(bypass deep nuclear cells) Also called vestibulo-cerebellum due to Also called vestibulo-cerebellum due to

connection with vestibular nuclei.connection with vestibular nuclei.

CEREBELLAR DISEASE:CEREBELLAR DISEASE:

Involvement of cerebellar cortex & 1 or Involvement of cerebellar cortex & 1 or more of deep cerebellar nuclei.more of deep cerebellar nuclei.

*No muscle paralysis & no sensory loss *No muscle paralysis & no sensory loss occurs. (MCQ)occurs. (MCQ)

FEATURES:FEATURES:1) ATAXIA:1) ATAXIA:

Incoordinate movements due to defect in Incoordinate movements due to defect in control of RANGE, DIRECTION, RATE & control of RANGE, DIRECTION, RATE & TIMING of movement.TIMING of movement.

Asynergia (no synergism between Asynergia (no synergism between agonists & antagonists; normal agonists & antagonists; normal synergism = when agonists contract, synergism = when agonists contract, antagonists relax).antagonists relax).

2) DYSMETRIA & PAST 2) DYSMETRIA & PAST POINTING:POINTING:

Inability to control range or extent of Inability to control range or extent of movement. movement.

Dysmetria Dysmetria also manifest as past also manifest as past pointing.pointing.

When patient tries to touch an object When patient tries to touch an object hand overshoots (past pointing).hand overshoots (past pointing).

3) ADIADOCOKINESIA / 3) ADIADOCOKINESIA / DYSDIADOCOKINESIA:DYSDIADOCOKINESIA:

Inability to perform RAPID, ALTERNATE, Inability to perform RAPID, ALTERNATE, OPPOSITE movement (rapid supination OPPOSITE movement (rapid supination & pronation of arm).& pronation of arm).

4) DRUNKEN GATE / 4) DRUNKEN GATE / STAGGERING GATE:STAGGERING GATE:

Patient walks on a broad base.Patient walks on a broad base. SPECIFIC POSTURE: Head is rotated & SPECIFIC POSTURE: Head is rotated &

flexed towards the side of lesion.flexed towards the side of lesion.

5) SLURRED SPEECH:5) SLURRED SPEECH:

Due to dysarthria ( disordered Due to dysarthria ( disordered articulation).articulation).

Incoordination of muscles of articulation.Incoordination of muscles of articulation. Some words or syllables are spoken loud Some words or syllables are spoken loud

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

are spoken short.are spoken short.

6) INTENTION TREMORS / 6) INTENTION TREMORS / ACTION TREMORS:ACTION TREMORS:

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

voluntary action.voluntary action. Example of drinking water from a cup.Example of drinking water from a cup.

7) REBOUND 7) REBOUND PHENOMENON:PHENOMENON:

Patient cannot stop a movement Patient cannot stop a movement abruptly.abruptly.

Example of flexion of elbow Example of flexion of elbow may hit may hit his face.his face.

8) DECOMPOSITION OF 8) DECOMPOSITION OF MOVEMENTS:MOVEMENTS:

Patient is not able to perform actions Patient is not able to perform actions involving simultaneous movement at involving simultaneous movement at more than 1 joint.more than 1 joint.

Movements are broken into components.Movements are broken into components. Loss of smooth progression of 1 Loss of smooth progression of 1

movement to other.movement to other.

9) NYSTAGMUS:9) NYSTAGMUS:

Rhythmic rapid movement of eyeballs Rhythmic rapid movement of eyeballs when eyes are focused on 1 side.when eyes are focused on 1 side.

Cerebellum has a damping function, Cerebellum has a damping function, which is disturbed.which is disturbed.

10) PENDULAR KNEE 10) PENDULAR KNEE JERK:JERK:

Due to loss of damping function of Due to loss of damping function of intermediate zone of cerebellum.intermediate zone of cerebellum.

11) HYPOTONIA:11) HYPOTONIA:

Due to loss of excitatory action of Due to loss of excitatory action of cerebellum on stretch reflex & muscle cerebellum on stretch reflex & muscle tone.tone.