cerebellum

Cerebellum

By

Dr. Noura El Tahawy

Magnetic resonance images of the cerebellum of a 16-year-old

female. A, sagittal slice.

Magnetic resonance images of the cerebellum of a 16-year-old female.

coronal slice. C,

Horizontal section through the cerebellum and brain stem.

Lobs

� Three deep fissures

� Primary fissure

� Horizontal fissure

� Posterolateral fissure

Three lobs

� Flocculonodular lobe

flocculus and nodule

� Anterior lobe

� Posterior lobe

Lobs

Primary fissure

Posterolateral fissureFlocculonodular lobe

Anterior lobe

Posterior lobe

corpus of

cerebellum

Cerebellum .A Viewed from above B Viewed from the position of the pons .

A Sagittal section of hindbrain .B Oblique section of cerebellum .

Internal

structure

� Cerebellar cortex

� Cerebellar Medulla (White matter)� Cerebellar nuclei

Dentate nucleus, Fastigial nucleus, Interposed

nucleus Emboliform nucleus

Globose nucleus

Gray matter

Internal structure

Cerebellar cortex

Dentate nucleus

Fastigial nucleus

Globose nuclei

Emboliform nucleus

medullary center

Cerebellar Cortex

Molecular Layer

Purkinje Cell Layer

Granular Layer

Corpus Medullare (Medullary Center)

Deep Cerebellar Nuclei

Fastigial Nuclei

Emboliform Nucleus

Globose Nucleus

Dentate Nucleus

Cerebellum Internal ConfigurationsCerebellum Cerebellum Internal ConfigurationsInternal Configurations

Transverse sections of cerebellar folia showing the layers of the cerebellar

cortex.

Transverse sections of cerebellar folia

Diagram shows afferent and efferent connections and their relationships to

the principal cells of the cerebellar cortex.

The cerebellar cortex

Cerebellar cortex .A Cell layers B Afferent system .C Internuncial neurons .D

Efferent system .

Three Anatomical Divisions

Three functional divisions

Schematic drawing of the cerebellum in which the peduncles have been cut and the surface flattened

out. The relationships between the anatomical and functional divisions of the cerebellum are shown.

(Green, archicerebellum; blue, paleocerebellum; pink, neocerebellum.)

� The archicerebellum corresponds to the flocculonodular lobe and

fastigial nucleus. Its principal connections are with the vestibular and

reticular nuclei of the brain stem and it is concerned with the

maintenance of equilibrium.

� The paleocerebellum corresponds to the vermis and paravermal area,

together with the globose and emboliform nuclei. It receives fibres

from the spinocerebellar tracts and projects to the red nucleus of the

midbrain.

� The neocerebellum corresponds to most of the cerebellar hemisphere

and the dentate nucleus. It receives afferents from the pons and

projects to the ventral lateral nucleus of the thalamus .

Three functional divisions

Connections & functions of the

cerebellum

Vestibulocerebellum

MLF

Summary of Main Connections of the Vestibulocerebellum

Summary of Main Connections of the Vestibulocerebellum

lower motor neuron

LMN

vestibulospinal

& Reticulospinal tracts

FASTIGIAL

NUCLEUS

Vestibular

OrganFloculonodular

Lobe Cortex

ARCHICEREBELLUM

VESTIBULAR NUCLEUS

Connections of the

Vestibulocerebellum

(archi-cerebellum).

(Contralateral projections of the fastigial nucleus are not shown).

Connections and function of Vestibulocerebellum

� The archicerebellum is primarily concerned with the maintenance of balance (equilibrium).

� It recieves afferents from the vestibular and reticular nuclei of the brain stem, passing through the inferior cerebellar peduncles.

� Vestibular information is then carried from the vestibular nuclei to the cortex of the ipsilateral flocculonodular lobe. Cortical cerebellar efferent (Purkinje cell) fibresproject to the fastigial nucleus, which, in turn, projects back to the vestibular nucleiand to the reticular formation.

� A significant proportion of fastigial efferents cross to the contralateral side of the brain stem.

� The influence of the archicerebellum upon the lower motor system is, therefore, bilateral and principally mediated by means of descending vestibulospinal and reticulospinal projections (both end in AHCs of spinal cord).

�

� Function: involved in eye movements and maintain balance

Spinocerebellum

Summary of Main Connections of the Paleocerebellum

Summary of Main Connections of the Paleocerebellum

lower motor neuron

SPINAL CORD

rubrospinal

tract

NUCLEUS

INTERPOSITUS

PALEOCEREBELLAR

Cortex

PALEOCEREBELLAR

Cortex

Inferior

Olivary

Nucleus

RED

NUCLEUS

spinocerebellar

tracts

(The Start)

Connections of the

Spinocerebellum

(Paleocerebellum)

� The paleocerebellum influences muscle tone and posture.

� Afferents consist principally of dorsal and ventral spinocerebellar tract neurones

that carry information from muscle, joint and cutaneous receptors and enter the

cerebellum through the inferior and superior cerebellar peduncles, respectively

� Fibres terminate largely in the cortex of the ipsilateral vermis and paravermis.

Cerebellar cortical efferents from these areas pass to the globose and emboliform

nuclei and also to the fastigial nucleus.

� The globose and emboliform nuclei project via the superior cerebellar peduncle to

the contralateral red nucleus of the midbrain, where they influence the activity of

cells giving rise to the descending rubrospinal tract .

Connections and function of Spinocerebellum

(Paleocerebellum)

Neocerebellum

CEREBRAL

CORTEX

CEREBRAL

CORTEXDENTATE

NUCLEUS

DENTATE

NUCLEUS

Summary of Main Connections of the Neocerebellum

Summary of Main Connections of the Neocerebellum

lower motor neuron

LMN

pyramidal

tract

NEOCEREBELLAR

Cortex

NEOCEREBELLAR

Cortex

THALAMUSLV nucleus

THALAMUSLV nucleus

Pontine

Nucleus

Pontine

Nucleus

Red nucleus

Connections of the Neocerebellum.

� The neocerebellum is concerned with muscular coordination, including the trajectory, speed and force of movements.

� The principal afferent pathway consists of pontocerebellar fibers ( . These originate in the pontine nuclei of the basal

portion of the pons and cross to the opposite side, entering the cerebellum through middle cerebellar peduncle

peduncle.

� Pontocerebellar neurons are influenced by widespread regions of the cerebral cortex involved in the planning and

execution of movement. Pontocerebellar fibres terminate predominantly in the lateral parts of the cerebellar

hemisphere.

� Output from the neocerebellar cortex is directed to the dentate nucleus. The dentate nucleus, in turn, projects to the

contralateral red nucleus and ventral lateral nucleus of the thalamus. The dentate is the largest of the cerebellar nuclei

and its efferents form a major part of the superior cerebellar peduncle.

� The fibres decussate in the caudal midbrain just before reaching the red nucleus. Some relay in the red nucleus with

rubrothalamic cells but most bypass the red nucleus and pass directly to the ventral lateral thalamus.

� The ventral lateral nucleus of the thalamus projects to the cerebral cortex, particularly the motor cortex of the frontal

lobe.

� The neocerebellum thus exerts its coordinating role in movement primarily through an action on cerebral cortical

areas, giving rise to descending corticospinal and corticobulbar pathways .

Connections and function of Neocerebellum

Arrows indicate directions of impulse conduction.

Principal cerebellar efferents.

Reticular

Formation

Reticular

Formation

CEREBELLUMCEREBELLUM

Summary Cerebellum and Automatic Motor Control

Summary Summary Cerebellum and Automatic Motor ControlCerebellum and Automatic Motor Control

Lower Motor Neuron (LMN)Lower Motor Neuron (LMN)Lower Motor Neuron (LMN)

Motor CortexMotor Cortex

Red NucleusRed Nucleus

Vestibular

Nucleus

Vestibular

Nucleus

ProprioceptorsProprioceptorsProprioceptors

��Maintenance of Equilibrium

- balance, posture, eye movement

�� Coordination of half-automatic movement of

walking and posture maintenance

- posture, gait

�� Adjustment of Muscle Tone

��Motor Learning – Motor Skills

�� Cognitive Function

Functions of the cerebellum

BalanceBalance


Motor Skills Motor Skills

Pablo CasalsPablo CasalsPablo Casals


Cerebellar SyndromeCerebellar Syndrome

� From this information the cerebellum coordinates the range, velocity and

strength of contractions to produce steady volitional movements and

steady volitional postures.

� Incoordination (ataxia) is the main feature of cerebellar dysfunction. An

easy way to remember a cerebellar syndrome is to imagine a drunken

person who cannot coordinate any volitional movement. He sways when

standing, reels when walking, slurs words when talking and has jerky

eye movements when looking.

� In addition, the muscles are loose and floppy (hypotonia).

Thus, ataxia, dysarthria, nystagmus and hypotonia are the four

major clinical signs of the cerebellar syndrome.

Posture

Gait – Ataxia

Tremor

Cerebellar Cerebellar

AtaxiaAtaxia

Ataxic gait and

position: Left

cerebellar tumor

a. Sways to the

right in standing

position

b. Steady on the

right leg

c. Unsteady on the

left leg

d. ataxic gait

a b c

d

Cerebellar tumors on Cerebellar tumors on vermisvermis

-- TruncalTruncal AtaxiaAtaxia

-- Frequent FallingFrequent Falling

The child in this picture:The child in this picture:

-- would not try to stand would not try to stand

unsupportedunsupported

-- would not let go of the bed railwould not let go of the bed rail

if she was stood on the floor.if she was stood on the floor.

Cerebellar Cerebellar

MedulloblastomaMedulloblastoma

Cerebellar Peduncles

Lateral aspect of the brain stem and cerebellum, showing the cerebellar

peduncles . Parts of the anterior, posterior and flocculonodular lobes have been

removed to display the peduncles more clearly .

Anteroinferior aspect of the cerebellum, Showing the three cerebellar peduncles

Anteroinferior aspect of the cerebellum., Showing the three cerebellar peduncles

Dissection of the left cerebellar hemisphere and its peduncles.

Diagram illustrating the composition of the cerebellar peduncles. A, dorsal

view. B, lateral view.

Downloaded from: Gray's Anatomy (on 25 July 2009 06:36 AM)

© 2007 Elsevier

Tractology of the cerebellum

(Cerebellar Peduncles)

1. Dentato-rubral

2. Dentato-thalamic

(LVN)

3. Dentato-olivary

4. Dentato-reticular

1. Cerebello-

pontine

1. Cerebello-olivary

2. Cerebello-vestibular

3. Cerebello-reticular

Efferents

1. Anterior

spinocerebellar

2. Tecto-cerebellar

1. Pontocerebellar1. Posterior

spinocerebellar

2. Cuneo-cerebellar

(posterior external

actuate fibers)

3. Olivo-cerebellar

4. Parolivo-cerebellar

5. Vestibulo-cerebellar

6. Reticulo-cerebellar

7. Anterior external

arcuate fibers

Afferents

Superior cerebellar

peduncles

Middle cerebellar

peduncles

Inferior cerebellar

peduncles

Blood Supply of the cerebellum

� The posterior inferior cerebellar artery (from

vertebral artery) supplies the cerebellum &the

side of the medulla

� The anterior inferior cerebellar and superior

cerebellar arteries (both arise from basilar

artery) supply the cerebellum& side of the pons

The arteries on the base of the brain.

You can download this lecture from:

http://www.slideshare.net/drnosman

Thanks

cerebellum

Health & Medicine