CEREBELLUM AND EXTRAPYRAMIDAL

SYSTEM

CEREBELLUMThe cerebellum is the third major

division of the brain located in the posterior cranial fossa.

The cerebellum helps to control balance and posture, coordination of skilled voluntary movement, movement planning and the command to move.

GROSS STRUCTURE

Cerebellum is a “miniature cerebral hemisphere”.

Hemispheres Furrows and Convolutions Lobes Functional Divisions Layers Nuclei Somatotopic Organization or

Homonculus

NUMBER OF HEMISPHERES & CONNECTING STRUCTURE

CEREBRUM 2 Symmetric

hemispheres (Right and Left) connected by the MEDIAL LONGITUDINAL FISSURE

CEREBELLUM2 Symmetric

hemispheres (Right and Left)

connected by the VERMIS

FURROWS AND CONVOLUTIONS

CEREBRUM (+) Deeper

Furrows known as Fissures and Shallower ones known as sulcus

(+)Convolutions known as gyri

CEREBELLUM Also has fissures

(ANTERIOR and POSTEROLATERAL)

Convolutions are not called gyri but the ridge-like folds are called FOLIA

LOBES

CEREBRUM5 (Frontal,

Parietal, temporal, occipital lobe and Insula.

CEREBELLUM3 (Anterior,

Posterior and Flocculonodular lobe)

FUNCTIONAL DIVISIONS

CEREBRUMAccording to

Brodmann’s Area

CEREBELLUMa. Traditional /

Transverse or Horizontal division

b. Vertical / Longitudinal Division

FUNCTIONAL DIVISIONSTRADITIONAL

ArchicerebellumPaleocerebellumNeocerebellum

VERTICAL Lateral Intermediate Vermal

ARCHICEREBELLUM

Oldest partFlocculonodular LobeLobule X of vermisFunctions for EQUILIBRIUM

PALEOCEREBELLUM

Anterior LobeLobule I – V of vermisFunction for PROPULSIVE,

STEREOTYPE MOVEMENTS

NEOCEREBELLUM

Most recent partPosterior LobeLobule VI – IX of VermisFunctions for COORDINATION OF

SKILLED VOLUNTARY MOVEMENTS, CONTROL OF EQUILIBRIUM AND MUSCLE TONE

VERTICAL / LONGITUDINAL DIVISION

VERMAL Vermis & Flocculonodular lobe

Fastigial (most medial nuclei)

INTERMEDIATE or PARAVERMAL

Most of Anterior lobe Interposed Nuclei (Globose & Emboliform)

LATERAL OR HEMISPHERIC Most of Posterior Lobe Dentate (most lateral nuclei)

LAYERS

CEREBRUMCerebral CortexSub-cortical

white matterBasal Nuclei

CEREBELLUMCerebellar CortexSub-cortical white

matterDeep cerebellar

Nuclei AKA ROOF NUCLEI

LAYERS AND CELLS OF THE CEREBELLAR CORTEX

LAYERS LOCATION TYPE / S OF NEURONAL CELL

FUNCTION OF NEURONAL CELL

MOLECULAR Outermost Stellate cell Basket cell

Inhibitory to Purkinje and Golgi Type II cells

PURKINJE CELL Middle layer Purkinje cell Inhibitory to cell bodies of deep cerebellar &

vestibular nuclei GRANULAR Innermost Granule cell

Golgi Type II cell Granule is Excitatory to other cells of the cortex

Golgi is Inhibitory to Granule cell

NUCLEI

CEREBRUMBasal nuclei

(Globus pallidus, Putamen and caudate nucleus)

CEREBELLUMCerebellar Nuclei

(from Medial to lateral) – FASTIGIAL, GLOBOSE, EMBOLIFORM AND DENTATE nuclei

SOMATOTOPIC ORGANIZATION OR HOMONCULUS

CEREBRUM Each side controls

CONTRALATERAL motor and sensory function of the body.

CEREBELLUMControl of the body is

IPSILATERAL a. VERMIS –

coordination & mm tone of trunk

b. LATERAL –coordination & mm tone of ipsilateral halves of limbs.

EXTERNAL ANATOMY

INFERIOR / VENTRAL ASPECT SUPERIOR / DORSAL ASPECT Cerebellar Peduncles (Superior,

Middle, Inferior) Flocculus Nodulus

Posterolateral Fissure Flocculonodular lobe

Vermis

Primary Fissure Anterior lobe Posterior lobe

Vermis

MIDSAGITTAL SECTION OF THE VERMIS

LOBULE LOCATION NAME I Anterior to Primary Fissure Lingula

II & III Anterior to Primary Fissure Central Lobule IV & V Anterior to Primary Fissure Culmen

VI Bet. Primary and Posterolateral Fissure Declive VII Bet. Primary and Posterolateral Fissure Folium & Tuber VIII Bet. Primary and Posterolateral Fissure Pyramis IX Bet. Primary and Posterolateral Fissure Uvula X Caudal to Posterolateral Fissure Nodulus

CONNECTIONS OF THE CEREBELLUM

1. Tectocerebellar tract2. Olivocerebellar tract3. Vestibulocerebellar tract4. Cuneocerebellar tract5. Dorsal spinocerebellar tract6. Cerebellar Peduncles

SUPERIOR CEREBELLAR MIDDLE CEREBELLAR

INFERIOR CEREBELLAR

OTHER NAME

Brachium Conjunctivum

Brachium Pontis Restiform body

LOCATION Midbrain Pons Medula Oblongata AFFERENT (SENSORY)

FIBER TRACTS

Ventral & some Rostral Spinocerebellar

Trigeminocerebellar Tectocerebellar

A lmost entirely crossed afferent

fibers from pontine nuclei Pontocerebellar

or Transverse Pontine fibers

Single afferent tract called the Fastigio-

bulbar tract or J uxtarestiform body

EFFERENT (MOTOR)

FIBER TRACTS

Predominantly contains efferent fiber tracts from cerebellum like the tract from the

deep cerebellar nuclei to rubralthalamic

projections

--- Chiefly Efferent: Vestibulocerebellar

Olivocerebellar Dorsal /Rostral

Spinocerebellar Cuneocerebellar Reticulocerebellar

EXTRAPYRAMIDAL SYSTEM

Voluntary movement is controlled by a complex motor circuit involving the cerebral cortex, brainstem, basal nuclei, cerebellum, thalamus and its corresponding tracts. Motor control is achieve because of the interaction of 3 neural structures namely the Pyramidal system, Extra-pyramidal system and Cerebellum.

PYRAMIDAL VS. EXTRAPYRAMIDAL SYSTEM

PYRAMIDAL SYSTEM (PS) EXTRAPYRAMIDAL SYSTEM (EPS) TRACTS Corticospinal Tract

Corticobulbar Tract Rubrospinal, reticulospinal,

Vestibulo-spinal and Tectospinal Tracts

FUNCTION Pathways that initiate voluntary motor function

Like the cerebellum, their nuclei and tracts modify or influence the voluntary motor output of the PS

LESION Loss of voluntary motor function or paralysis

Movement disorders (Hypo or Hyperkinetic movements)

STRUCTURES OF THE EXTRAPYRAMIDAL SYSTEM

The extra-pyramidal system includes all descending motor tracts other than corticospinal and corticobulbar tracts.

Nerve impulses along this pathway follow a complex, polysynaptic circuit that involves the motor cortex, basal nuclei, limbic system, thalamus, cerebellum, reticular formation and nuclei in the brainstem

EXTRAPYRAMIDAL (INDIRECT) PATHWAYS

PATHWAYS ORIGIN DESTINATION FUNCTION RUBROSPINAL Red Nucleus Anterior Horn Cell

to muscles on opposite side

Motor – Precise discrete mov’t of

hands & feet TECTOSPINAL Tectum of

Midbrain (Sup. Colliculus)

Ant. Horn inter-neurons to skeletal

mm on opposite side

Reflex head turning following sudden vi-

sual and auditory stim

VESTIBULOSPINAL Lateral Vestibular Nucleus

Anterior horn Cell (Extensors)

Postural reflexes & Control of mm tone Facilitate quick rxn.

LATERAL RETICULOSPINAL

Reticular Formation

Anterior and Posterior Horn

Facilitate Flexor Ref. Inhibit Extensor Ref. Decrease mm tone

MEDIAL RETICULOSPINAL

Pons Reticular Formation

Anterior and Posterior Horn

Facilitate Extensor R. Inhibit Flexor Ref. Increase mm. tone

LESIONS OF THE EXTRAPYRAMIDAL SYSTEM

PART OF EPS LESION STRIATUM Chorea

CAUDATE NUCLEUS Huntington Chorea GLOBBUS PALLIDUS Rigidity

SUBTHALAMIC NUNCLEUS OF LUYS Ballismus or Hemiballismus SUBSTANTIA NIGRA Parkinson’s Dse.

RED NUCLEUS Chorea

END OF LECTURE!!!

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