cerebellum

Cerebellum Lecture Class by

Pratap Sagar Tiwari, MD, Lecturer, NGMC

Nervous System Development : Anatomical subdivisions

Source : http://en.wikipedia.org/wiki/File:EmbryonicBrain.svgReference: Gray’s Anatomy

Nervous System Development : Anatomical subdivisions

Primary division of neural tube

Sec. subdivision Final segments

Prosencephalon 1. Telencephalon2. Diencephalon

1. The cortex, Caudate, Putamen, Globus pallidus 2. Thalamus, hypothalamus, subthalamus, subthalamic nuclei

Mesencephalon Mesencephalon Mesencephalon (Midbrain), Substantia nigra pars compacta (SNc), Substantia nigra pars reticulata (SNr)

Rombencephalon 1. Metencephalon2. Myelencephalon

1. Pons and cerebellum2. Medulla

The cerebellum is divided into anatomically distinct lobes.The main body of cerebellum has three functional regions: the central vermis and the lateral and intermediate zones in each hemisphere. It is divided by the primary fissure into anterior and posterior lobes. The posterolateral fissure separates the flocculonodular lobe.

The Cerebellum Has Three Functionally Distinct Regions

Cerebellum & its connections

Connections with brainstem:• Superior cerebellar peduncle connects to

midbrain• Middle cerebellar peduncle connects to pons• Inferior cerebellar peduncle connects to

medulla

Afferent connections with spinal cord and brain

Afferent connections with spinal cord and brainCortico-cerebellar projectionVentral spinocerebellar tractDorsal spinocerebellar tract

Efferent connections

Efferent connectionsThalamusRed nucleusReticular formationVestibular nucleus

Sections of the Cerebellum

Vestibulocerebellum or archicerebellum• Comprises the flocculonodular lobe• Extensive connections with the vestibular systemSpinocerebellum or paleocerebellum• Comprises the vermis (medial) & paravermal (intermediate) region• Extensive connections with the spinal cord & brainstemCerebrocerebellum or neocerebellum• Comprises lateral portions of cerebellar hemispheres (excluding

paravermal regions)• Extensive connections with cerebral cortex through relay stations

in cerebellar nuclei and dorsal thalamus

CEREBELLAR PEDUNCLES

Superior cerebellar peduncle (brachium conjunctivum)

• Connects to midbrainAfferents: only ventral spinocerebellar tractEfferents:• Most of the efferents from the cerebellum• All of the efferents from three (out of four)

pairs of nuclei: dentate, emboliform, and globose

Middle cerebellar peduncle (brachium pontis)

• Connects to ponsAfferents: from cerebral cortex (“corticoponto-cerebellar system”).Corticopontine projections (originating in the cerebral cortex) synapse in ipsilateral basal pons. From there, most pontocerebellar projections decussate, pass through middle cerebellar peduncle and enter cerebellum.• A small number remain ipsilateral.Efferents: none.

Inferior cerebellar peduncle (“corpus restiform” or “restiform body”)

• Connects to medulla• Two components:• Restiform body

– Afferents:• Ascending spinal proprioceptive fibers from three of the spinocerebellar tracts

(dorsal, rostral, and cuneocerebellar)• Ascending fibers from contralateral inferior olivary nuclei to cerebellar cortex

(olivocerebellar projections)• Reciprocal connections with motor reticular formation and spinocerebellum

(paleocerebellum): reticulocerebellar and cerebelloreticular projections

• Juxtarestiform body– Mostly contains reciprocal connections to and from vestibulocerebellum

(archicerebellum) and vermal portion of spinocerebellum (paleocerebellum): vestibulocerebellar and cerebellovestibular fibers

Cerebellar Cortex

Deep Cerebellar Nuclei:Dentate

InterposedFastigial

PNS Fig. 42-1

General View

Gross features of the cerebellum, including the nuclei, cerebellar peduncles, lobes, folia, and fissures. (Adapted from Nieuwenhuys et al. 1988)A. Dorsal view. Part of the right hemisphere has been cut out to show the underlying cerebellar peduncles.B. Ventral view of the cerebellum detached from the brain stem.C. Midsagittal section through the brain stem and cerebellum, showing the branching structures of the cerebellum.

upper motor neuron

UMN

upper motor neuron

UMN

BASALGANGLIA

BASALGANGLIA

Pyramidal Tract and Associated CircuitsPyramidal Tract and Associated Circuits

lower motor neuron

UMN

lower motor neuron

UMN

pyramidal tract

CerebellumCerebellum

Motor Hierarchy

Exerts influenceat all levels

Intent

Actual

1° Som sensory

IVth vent VermisIntermediate hem.

Spinocerebellum: Vermis Intermediate hem.Spinocerebellum

(Vermis + Intermed. Hem)

Control of limbs and trunk

Lateral hem.

Cerebrocerebellum: Lateral hem.

Cerebrocerebellum(Lateral hemisphere)

Planning of movement+

Floculo-nodular lobe

Vestibulo-cerebellum(Floculo-nodular lobe)

Control of eye & head movementsBalance

Cerebellar divisions

NTA Fig. 13-1

Inputs and Outputs of Cerebellum

The Cerebellum Has Three Functionally Distinct Regions

Cerebellar CortexInputs

Output

Interneurons

Climbing fibers•from Inferior olive

Mossy fibers

Purkinje neurons

Stellate neurons

Granule neurons

Basket neurons

Golgi neuronsMolecular

PurkinjeGranular

NTA Fig. 13-11

The Cerebellum Has Three Functionally Distinct Regions

The three functional regions of the cerebellum have different inputs and outputs.

Cerebellar Ataxia

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 dysfunction

Dysfunction: damage produces the following:• Ataxia- a disturbance that alters the direction andextent of voluntary movements; abnormal gait anduncoordinated movements• Dysmetria- altered range of motion (misjudge distance)• Intention Tremor-oscillating motion, especially of head,during movement• Vestibular signs-nystagmus, held tilt

Cerebellar dysfunction

1. Small lesions produce no signs or only transient symptoms; small deficits are compensated for by other parts of the brain2. Lesions of the cerebellar hemispheres result inloss of muscular coordination and jerky puppet-like movements of the limbs on the ipsilateral side (same side as lesion)3. Lesions of the vermis result in truncal tremorand gait ataxia (splayed stance and swaying ofthe body while walking)[

References