Brain Anatomy: Cerebellum

Brain Anatomy: Cerebellum

SMS 1084 Dr. Mohanad R. Alwan

Cerebellum 

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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 Interposed Fastigial

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. 

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The Cerebellum 

The cerebellum 

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

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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  

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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 

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Located dorsal to pons and medulla In posterior fossa under tentorium cerebelli Lobes 

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Floccular Nodular(small fluffy mass) Anterior Posterior

Flattened Cerebellum 

Longitudinally separated into hemispheres and cortices  Median (Vermal)

Vermis=worm 

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Paramedian (Paravermal Lateral

Cerebellar Anatomy Transverse division  Anterior Lobe  ------------ primary fissure  Posterior Lobe  ------------ posterolateral fissure  Flocculonodular Lobe

Cerebellum Median

Prepyramidal Fissure Posterolateral Fissure 16

Paramedian Primary Fissure Posterior Superior Fissure

Horizontal Fissure

Cerebellum  

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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 

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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         

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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

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Granular Cell

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-- 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

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"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)

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Dentate nucleus 

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Largest, communicates through cerebellar peduncle Carries information important for coordination of limb movements (along with the motor cortex and basal ganglia)

Dentate Nucleus

Pontine Projections Pons

Dentate Nucleus Superior Cerebellar Peduncle

Cerebellar Nuclei

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Emboliform nucleus (medial side of the nucleus dentatus) 

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Globose nucleus 

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Regulates movements of ipsilateral extremity Regulates movements of ipsilateral extremity

Fastigial nucleus  

Regulates body posture Is related to the flocculo nodular lobe

Cerebellum Deep Nuclei 1. Fastigial

nucleus 2. Globose nucleus 3. Emboliform nucleus 4. Dentate nucleus

Cerebellar Cortex

Deep Cerebellar Nuclei: Dentate Interposed Fastigial

Input-output Organization Cerebellar cortex

Deep Cerebellar Nuclei: Fastigial Interposed Dendate

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Cortex

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Output

Vestibular nuclei

Extrinsic inputs: mossy fiber climbing fiber

Spinocerebellum: Vermis Intermediate hem. Cerebrocerebellum: Lateral hem.

Spinocerebellum (Vermis + Intermed. Hem) Control of limbs and trunk

Cerebrocerebellum (Lateral hemisphere) Planning of movement+

Vestibulo-cerebellum (Floculo-nodular lobe)

IVth vent

Vermis Intermediate hem. Lateral hem.

Control of eye & head movements Balance Floculo-nodular lobe