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CEREBELLAR CONTROL OF MOVEMENTS

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CEREBELLAR CONTROL OF MOVEMENTS

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ORGANIZATION OF CEREBELLUM

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FUNCTIONAL ORGANIZATION OF CEREBELLUM

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INPUT OF CEREBELLUM

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CEREBELLAR OUTPUT

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VESTIBULOCEREBELLUM

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NEOCEREBELLUM

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THE SPINOCEREBELLUM CONTAINS TWO SOMATOTOPIC NEURAL MAPS OF THE BODY

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CEREBELLAR PATHWAY

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CEREBELLUM:ANATOMY,CONNECTIONS,&FUNCTIONS

Dr.Rupjyoti Das

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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.

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 &

separated from cerebrum by tentorium cerebelli.

Weight=150 gm

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On axial & coronal planes,a midline portion,the vermis, and two lateral portions, the cerebellar hemispheres,can be recognized.

The vermis is developmetally older & receives mainly spinocerebellar afferents, whereas the hemispheres have more complex fibre connections.

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SCHEMATIC REPRESENTATION OF THE MAJOR ANATOMICAL SUBDIVISIONS OF THE CEREBELLUM.

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The cortex is convoluted into many folia. Three major transverse divisions (lobes) are

recognized— The anterior lobe is most rostral, posterior lobe and flocculo-nodular lobe more

caudally. These lobes are divided by the primary fissure

and the posterolateral fissure, respectively. Larsell described 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.

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Spinocerebellum

Pontocerebellum

Vestibulocerebellum

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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.

The cerebellum receives nearly 200 million input fibres.

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Anatomical division- : the anterior lobe (rostral to the "primary

fissure"), the posterior lobe (dorsal to the "primary

fissure") and the flocculonodular lobe, The first two can be further divided in a

midline cerebellar vermis and lateral cerebellar hemispheres.

THE CEREBELLUM CAN BE DIVIDED ACCORDING TO THREE DIFFERENT CRITERIA: GROSS ANATOMICAL, PHYOLOGENETICAL, AND FUNCTIONAL:

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Classification by Phylogenetic and Ontogenic Development :

Archicerebellum Paleocerebllum Neocerebellum

Classification by Afferent Connection

Vestibulocerebellum Spinocerebellum Pontocerebellum

Classification by Efferent Connection

Vermis Paravermal Region Cerebellar Hemisphere

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Functional denomination (phylogenetic denomination)

Anatomical parts Role

Vestibulocerebellum (Archicerebellum)

Flocculonodular lobe (and immediately adjacent vermis)

The vestibulo cerebellum regulates balance and eye movements. Lesions of the vestibulo cerebellum cause disturbances of balance and gait.

FROM THE PHYLOGENETICALLY OLDEST TO THE NEWEST, THE THREE PARTS ARE:

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Spinocerebellum (Paleocerebellum)

Vermis and intermediate parts of the hemispheres ("paravermis")

The spino cerebellum regulates body & limb movements.The spino cerebellum is able to elaborate proprioceptive input in order to anticipate the future position of a body part during the course of a movement.

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Cerebrocerebellum (Neocerebellum)

Middle portion of the vermis & Lateral parts of the hemispheres

The neo cerebellum is involved in planning & initiation of movement.It has purely cognitive functions as well.

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During the early stages of embryonic development, the brain starts to form in three distinct segments:

the prosencephalon, mesencephalon, and rhombencephalon. The rhombencephalon is the most caudal

(toward the tail) segment of the embryonic brain.

DEVELOPMENT OF CEREBELLUM

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Archicerebellum (nodulus)

Archicerebellum (flocculus) Paleocerebellum

Neocerebellum

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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.

The specific rhombomeres from which the cerebellum forms are rhombomere 1 (Rh.1) caudally (near the tail) and the "isthmus" rostrally (near the front).

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The cerebellum is of archipalliar phylogenetic 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.

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Subdivision of Flocculonodular Lobe

Nodulus Flocculus

Subdivision of Anterior Lobe

Vermis Hemisphere

Lingula Central Lobule Ala Central Lobule

postcentral fissure

Culmen Quadriangular Lobule

CEREBELLUM-EXTERNAL CONFIGURATION

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Subdivision of Posterior Lobe

Vermis Hemisphere

Declive Simple Lobule

postcentral fissure

Folium Superior Semilunar Lobule horizontal fissure

Inferior Semilunar Lobule Tuber Gracile Lobule prepyramidal fissure

Pyramid Biventral Lobule

secondary fissure

Uvula Tonsil

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Grey matter of cerebellum:

1.Cerebellar cortex.

2.Cerebellar nuclei

CYTOARCHITECTURE

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1.Molecular layer Consists mainly of neuropil and is the site of synapses. Contains scanty neurons consisting of stellate and basket

cells.

2.Purkinje cell (Piriform) layer Single layer of neurons. Consists of large (25 micrometer) pear-shaped neurons .

3.Granular cell layer Very small(7 micrometer) granular neurons. Very numerous – 3 to 7 million neurons per cubic mm.

4.White matter – forms the core of the foliae.

THE CEREBELLAR CORTEX CONSISTS OF THREE LAYERS ON A CORE OF WHITE MATTER.

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1.Outer stellate layer(In molecular layer)

2.Basket cells ( -do- )

3.Purkinje cells.

4.Granule cells. (In granule cell layer)

5.Golgi cells ( -do- )

NEURONS OF CEREBELLAR CORTEX

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The white matter of the cerebellum is made up of intrinsic,afferent & efferent fibres.

Incoming impulses to the cerebellum reach the dendrites and cell bodies of Purkinje cells.

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.

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The climbing fibres are the terminal fibres of the olivocerebellar tracts & make multiple synaptic contacts with one Purkinje cell.

The mossy fibre system 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.

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The multilayered fibre system includes afferents to the cerebellum from the hypothalamus,raphe nuclei & locus ceruleus & projects into the cerebellar cortex & deep cerebellar nuclei.

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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.

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8. PARALLEL FIBER

9. INFERIOR OLIVA

NUCLEUS 0. D L

NUCLEI 1. Purkinje cell

2. granule cell

3. basket cell

4. Golgi cell

5. stellate cell

6. climbing fiber

7. mossy fiber

8. parallel fiber

9. inferior olivary nucleus

10. deep cerebellar nuclei

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The Purkinje cells are central neurons  (everything else converges on them)

They consist of= 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.

A large cell body.  An axon  which forms the efferent pathway from

the cerebellum , and  sends collaterals in the granular layer.

GABA is the main neurotransmitter. 

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The Granule cells:

Very numerous: 3-7 million / mm3 Very small (7mm), closely packed neurons. Heterochromatic nuclei, scanty cytoplasm. Small dendritic tree in granule layer.

An unmyelinated axon. Directed to molecular layer (centrifugal). *Splits in T-shape manner to form parallel fibre.

Parallel fibers run longitudinally along folia Cross dendrites of many Purkinje cells. Have glutamate as neurotransmitter. 

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Cerebellar Neurons are Stimulatory or Inhibitory to Purkinje Cells.

Climbing fibres are strongly excitatory. Mossy fibres stimulate granule cells. Parallel fibres of granule cells stimulate several

Purkinje cells simultaneously. Basket cells strongly inhibit Purkinje cells. Stellate cells inhibit Purkinje cell dendrites. Golgi Type II cells inhibit directly the mossy fibre input.

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Main neurotransmitter= L-glutamate. Afferents reaching Purkinje through (Mossy/Climbing fibres) :Excitatory.

Purkinje cells =GABAergic. Golgi cells= -do- Stellate cells = -do- Basket cells = -do-

NEUROCHEMISTRY

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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:

From lateral to medial, they are the dentate, emboliform, globose, and fastigial.

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Dentate n.

Emboliform n. Globose n.

Fastigial n.

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These nuclei receive inhibitory (GABAergic) inputs from Purkinje cells in the cerebellar cortex and

excitatory (glutamatergic) inputs from mossy fibre pathways.

Most output fibers of the cerebellum originate from these nuclei.

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The fastigial nucleus assists stance & gait & controls muscles only in the modes of sitting,standing & walking.

The nucleus interposed assists segmental reflexes & speeds the initiation of movement triggered by somatosensory cues.

The dentate nucleus assists in tasks requiring fine dextirity.

EACH NUCLEUS CONTROLS A DIFF.TYPE OF MOVEMENT AS FOLLOWS:

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The cerebellum follows the trend of "threes", with three major input and output peduncles (fiber bundles). These are

the superior (brachium conjunctivum), middle (brachium pontis), and inferior (restiform body) cerebellar

peduncles.

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Peduncle Description

SUPERIOR

some afferent fibers from the anterior spinocerebellar pass to the anterior cerebellar lobe via this peduncle. Thus, the superior cerebellar peduncle is the major output pathway of the cerebellum. Most of the efferent fibers originate within the dentate nu.which in turn project to various midbrain structures including the red nucleus, the ventral lat./ventral ant. nucleus of the thalamus, and the medulla. The dentatorubrothalamo cortical& cerebellothalamocortical pathways are two major pathways that pass through this peduncle and are important in motor planning.

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MIDDLE

This is composed entirely of afferent fibers originating within the pontine nuclei as part of the massive corticoponto cerebellar tract.These fibers descend from the sensory and motor areas of the cerebral neocortex and make the middle cerebellar peduncle the largest of the three cerebellar peduncles.

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INFERIOR

Proprioceptive information from the body is carried to the cerebellum via the dorsal spinocerebellar tract. This tract passes through the inferior cerebellar peduncle and synapses within the paleocerebellum. Vestibular information projects onto the archicerebellum.The climbing fibers of the inferior olive run through the inferior cerebellar peduncle.This peduncle also carries information from the Purkinje cells to the vestibular nuclei in the dorsal brainstem located at the junction between the pons and medulla.

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Tracts or fiber bundles Distribution

Inferior cerebellar peduncle

Afferent paths Olivocerebellar tract

Lateral hemispheres and cerebellar

nucleus

Paraolivocerebellar tract Vermis, paravermis. and cerebellar

nucleus

Vestibulocerebellar tract Fastigial nucleus, flocculonodular lobe, and uvula

Reticulocerebellar tract Spinal region of cerebellar vermis

Posterior spinocerebellar tract Hind limb region of cerebellar cortex

Trigeminocerebellar tract Dentate and emboliform nucleus

Cuneocerebellar tract Forelimb and upper trunk region of cerebellar cortex

Anterior exterior arcuate fibers Flocculus

Arcuatocerebellar fibers  (striae medullares) Flocculus

Efferent paths Cerebellovestibular tract Vestibular nucleus

Cerebelloreticular tract Pontine and medullary reticular nucleus

CEREBELLAR CONNECTIONS--

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Middle cerebellar peduncle

Afferent paths Pontocerebellar tract Neocerebellar cortex

Superior cerebellar peduncle

Afferent paths

Anterior spinocerebellar tract Hind limb region of cerebellar cortex

Tectocerebellar tract Intermediate vermis and lobulus

simplex

Trigeminocerebellar tract

Efferent paths

Dentatorubral fibers Red nucleus

Dentatothalamic fibers Ventral intermediate (VI) and ventral

anterior (VA) nucleus of thalamus

Fastigioreticular fibers Reticular nucleus of midbrain, pons,

and medulla oblongata

CONT.

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Afferent connection

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MAIN CONNECTIONS OF THE VESTIBULOCEREBELLUM

Floculonodular

Lobe

Vermis

FASTIGIAL NUCLEUS

VESTIBULAR NUCLEUS

Vestibular Organ

lower motor neuron LMN

ARCHICEREBELLUM

vestibulospinal tractMLF

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RED NUCLEUS

MAIN CONNECTIONS OF THE PALEOCEREBELLUM

RED NUCLEUSNUCLEUS

INTERPOSITUS

ANTERIOR LOBE

PARAVERMAL ZONE

PALEOCEREBELLUM

Inferior OlivryNucleusLower

motor neuronSPINAL CORD

Rubrospinal tract

spinocerebellar tract

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MAIN CONNECTIONS OF THE NEOCEREBELLUM

CEREBRAL CORTEX THALAMUS

PontineNucleus

Lower motor neuron

LMN

DENTATENUCLEUS

POSTERIOR LOBE

CEREBELLAR HEMISPHERE

NEOCEREBELLUM

Pyramidal tract

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CEREBELLUM AND AUTOMATIC MOTOR CONTROL

CEREBELLUM

MOTOR CORTEX

RED NUCLEUS

VESTIBULAR

NUCLEUS

RETICULAR FORMATION

LOWER MOTOR NEURONProprioceptor

s

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Corticonuclear Connections

A zone ---------- fastigial nucleus medial vestibular nucleus B zone ---------- lateral vestibular nucleus

C1, C3 zone --- emboliform nucleus C2 ---------------- globose nucleus

D1 ---------------- parvocellular portion of dentate nucleus D2 ---------------- magnocellular portion of dentate nucleus

VOOGD ORIGINALLY DESCRIBED 4 ZONES, FROM MEDIAL TO LATERAL--

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1. vermis

2. paravermal region

3. cerebella hemisphere

4. nodulus

5. flocculus

6. fastigial nucleus

7. globose nucleus

8. emboliform nucleus

9. dentate nucleus

10. medial vestibular

nucleus

11. lateral vestibular

nucleus

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The inferior olivary nucleus or inferior olive comprises 3 major divisions –

the principal olive (PO), the dorsal accessory olive (DAO) and the medial accessory olive (MAO). 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.

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Olivocerebellar Connections

Caudal portion of medial and dorsal accessory olivary nucleus ----------------- vermis of cerebellar cortex (A and B) fastigial nucleus vestibular nucleus

Rostral portion of medial and dorsal accessory olivary nucleus ----------------- paravermal region (C1, C2, C3) nucleus interpositus

Principal Inferior Olivary Nucleus ----------------- cerebellar hemisphere (D1, D2) dentate nucleus

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Caudal portion

Rostral portion

Principal inferior olivary nucleusmedial and dorsal accessory olivary nucleus

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The posterior inferior cerebellar artery (PICA): supplies-

Lat.medullary tegmentum, inferior cerebellar peduncle The ipsilat.portion of the inferior vermis & the inferior surface of the cerebellar

hemisphere. The medial br. of the PICA supplies the

medial cerebellum & the dorsolat. Medulla oblongata.

The lateral br.supplies the inferoposterolat. aspect of the cerebellum.

VASCULAR SUPPLY OF THE CEREBELLUM:

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The ant.inf.cerebellar artery (AICA) supplies- Ant.petrosal surface of the cerebellar hemisphere, Flocculus, Lower portion of the middle cerebellar peduncle & Lat.pontomedullary tegmentum

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The superior cerebellar artery (SCA) supplies- The upper surface of the cerebellar

hemisphere, Ipsilat.portion of the superior vermis, Most of the dentate nucleus, Upper portion of the MCP,SCP & lat.pontine

tegmentum.

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Maintenance of Equilibrium - balance, posture, eye movement

Coordination of half-automatic movement of walking and posture maintenace - posture, gait

Adjustment of Muscle Tone

Motor Leaning – Motor Skills

Cognitive Function

CEREBELLUM:FUNCTIONS

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BALANCE

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MOTOR SKILLS

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ARCHICEREBELUM Floculonodular lobe- Vestibulocerebelum Function:

Maintenance of equilibrium Suppress Vestibulo Ocular Reflex Muscle tone in relation to head posture

Animal ablation Disorder of equilibrium Positional nystagmus

Human: Meduloblastoma Trunkal ataxia Vestibular nystagmus (fast component towards the side of lesion) Positional nystagmus does not fatigue Vertigo

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PALLEO-CEREBELUM Anterior lobe + Vermis Afferent:

Spinocerebellar tract Spino-> olivo->cerebellar Spino -> reticulo -> cerebellar

Efferent Festigio -> vestibulo -> spinal Festigio -> Reticulo -> Spinal

Function Tone control Posture of axial muscle Equilibrium and locomotion

Animal ablation Increased lengthening and

shortening Increased tendon reflex Exagerated postural reflex

(positive supporting reflex) Human

Alcoholic degeneration Cerebellar degeneration Gait ataxia Rarely mild hypotonia,

dysmetria and dysarthria

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NEOCEREBELUM Ablation in Dog and Cat inconstant result Monkey ablation

Hypotonia Clumsiness of ipsilateral limb Dentate nucleus ablation -> more enduring

effect intension tremor

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CEREBELLAR ZONES1. Vermis zone: control posture, tone, locomotion, equilibrium

i. Vestibular connection project to festigial nucleusii. Control position of the head in relation to trunk and extraocular

movments

2. Intermediate zonei. Affrent-

a. proprioceptive from limbb. Sensorimotor cortexc. Collateral from corticospinal tract

ii. Efferent globos and embodiform nucleus ->VL thalamus to motor cortex

iii. Function: Regulation of movment via sensory feedback from the corticospinal muscle

a. Control velocity, force, pattern of movement

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CEREBELLAR ZONES: LATERAL Afferent: motor and sensory association cortex Efferent: Dantate -> thalamus -> motor cortex (open loop) Function: Programing of movement before initiation Animal: coordination of ipsilateral movment Human: Hypotonia- flabby muscle, abnormal posture

(slopping of shoulder) increased excursion of outstretched hand tapping. Hyperflexibility of joint, pendular reflex knee

Cerebellum control separately the activity of alpha and gamma motor neuron

Reduced fusimotor activity from abnormal long loop reflex through precentral cortex

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CEREBELLAR DYSFUNCTION1. Ataxia: Limb, gait and speech2. Speech: Scanning3. Tremor: Postural, intention, limb, trunk and head4. Tone: Hypotonia -> Hyperextensibility, pendular knee jerk,

rebound phenomenon5. Voluntary movement: Dysmetria, dysynergia,

disdidokokinesia6. Gait: ataxic, truncal ataxia7. Head tilt8. Postural abnormality: due to unequal hypotonia of truncal

muscle -> scoliosis, elevation or depression of shoulder, pelvic tilt

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3VOLUNTARY MOVEMENT ABNORMALITY Gorden Holms : Rate, range and force

Dyssynergia: Disruption of the normal smooth control of movement provided by gradual contraction of synergic muscle and relaxation of their antagonist

Voluntary movement- longer to start and longer to stop Prolongation of interval between the command and triphasic

agonist- antagonist and motor sequence Agonist burst may be too long or short or continue into the

antagonist burst -> dysmetria and dysenergia Rebound phenomenon (abnormal check reflex) Dysdiadokokinesia Decomposition of movement

Scanning speech Cogwheel eye moevment

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3VOLUNTARY MOVEMENT ABNORMALITY Dysmetria

Inability of the sensorimotor apparatus to measure distance in the course of movement

Hypometria and hypermetria of the limb and eye Tremor : Postural and intention Ataxia of gait: falling towards the side of lesion Nystagmus:

Gaze paretic (evoked) deviation Downbeat Rebound Sustained horizontal Opsoclonus Skew deviation

Weakness, faitibability and loss of associted movement

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