Brain Anatomy: Cerebellum

SMS 1084

Dr. Mohanad R. Alwan

Cerebellum The cerebellum is located behind the dorsal

aspect of the pons and the medulla. A midline portion, the vermis, separates two

lateral lobes, or cerebellar hemispheres.

The cerebellum consists of the cerebellar cortex and the underlying cerebellar white matter

Four paired deep cerebellar nuclei are located within the white matter of the cerebellum.

Because of the location of the fourth ventricle, ventral to the cerebellum, mass lesions or swelling of the cerebellum can cause obstructive hydrocephalus.

Cerebellum

Cerebellar Cortex

Deep Cerebellar Nuclei:Dentate

InterposedFastigial

Cerebellar functions The cerebellum has several main functions:

Coordinating skilled voluntary movements by influencing muscle activity,

Controlling equilibrium and muscle tone through connections with the vestibular system and the spinal cord and its gamma motor neurons.

There is a somatotopic organization of body parts within the cerebellar cortex.

In addition, the cerebellum receives collateral input from the sensory and special sensory systems.

The Cerebellum The cerebellum

Is important for coordination and error checking during motor, perceptual, and cognitive functions

The cerebellum Is also involved in learning and

remembering motor skills

Functions Co-ordination of movement The cortex initiates it and the

cerebellum co-ordinates it.

Damage to the cerebellum

Causes a lack of co-ordination: Speaking Walking Tremour

Cerebellar Stroke

Dizziness, vomiting Unsteady so that walking is

impossible Power, tone and reflexes normal

Area of blood in the cerebellum would show on a CT scan

Cerebellar Anatomy

Located dorsal to pons and medulla

In posterior fossa under tentorium cerebelli

Lobes Floccular

Nodular(small fluffy mass)

Anterior Posterior

Flattened Cerebellum

Longitudinally separated into hemispheres and cortices Median

(Vermal)Vermis=worm

Paramedian (Paravermal

Lateral

Cerebellar Anatomy

Transverse division Anterior Lobe ------------ primary fissure Posterior Lobe ------------ posterolateral fissure Flocculonodular Lobe

16

Cerebellum

Median Paramedian PrimaryFissure

PosteriorSuperiorFissure

HorizontalFissure

Posterolateral Fissure

Prepyramidal Fissure

Cerebellum

Cerebellar Cortex Molecular Layer Purkinje Cell Layer Granular Layer Corpus Medullare (Medullary Center) Deep Cerebellar Nuclei Fastigial Nuclei Nucleus Interpositus Emboliform Nucleus Globose Nucleus Dentate Nucleus

Cerebellar Cortex

Cerebellar Cortex I. Molecular Layer Stellate Cell --- taurine (inhibitory) afferent: parallel fiber efferent: Purkinje cell dendrite Basket Cell ---- GABA (inhibitory) afferent: parallel fiber efferent: Purkinje cell soma Parallel Fiber granule cell axon

Purkinje Cell Dendrite

Cerebellar Cortex

II. Purkinje Cell Layer Purkinje Cell -- 15,000,000 in number -- GABA (inhibitory) afferent: parallel fiber climbing fiber stellate cell basket cell efferent: deep cortical nuclei

Bergman’s glial cell

Cerebellar Cortex

III. Granular Layer

Granular Cell -- 50,000,000,000 in number -- glutamic acid (excitatory) afferent: mossy fiber efferent: Purkinje cell dendrite basket cell, stellate cell Golgi cell Golgi Cell -- GABA (inhibitory) afferent: parallel fiber, mossy fiber rosette efferent: granule cell dendrite

Cerebellar Cortex

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

Tentorium cerebelli

"tent of the cerebellum"

dura mater that separates the cerebellum from the inferior portion of the occipital lobes.

Cerebellar Nuclei (Nuclei = deep cluster of neurons)

Dentate nucleus

Largest, communicates through cerebellar peduncle

Carries information important for coordination of limb movements (along with the motor cortex and basal ganglia)

Dentate Nucleus

Pons

PontineProjections

DentateNucleus

SuperiorCerebellarPeduncle

Cerebellar Nuclei

Emboliform nucleus (medial side of the nucleus dentatus) Regulates movements of ipsilateral extremity

Globose nucleus Regulates movements of ipsilateral extremity

Fastigial nucleus Regulates body posture Is related to the flocculo nodular lobe

Cerebellum

Deep Nucleiuclei

11. . Fastigial

nucleus

2. Globose

nucleus

3. Emboliform

nucleus

4. Dentate nucleus

Cerebellar Cortex

Deep Cerebellar Nuclei:Dentate

InterposedFastigial

Input-output Organization

Cerebellarcortex

FastigialInterposedDendate

Deep Cerebellar Nuclei:

Vestibularnuclei

Cortex

Nuclei

Output

Extrinsic inputs: mossy fiber climbing fiber

+-

+

+

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