Lecture 3 - Cerebellum

What is the cerebellum and where is it located?

The cerebellum is a part of the hindbrain located in the posterior cranial fossa behind the pons and medulla oblongata, separated from them by the cavity of the fourth ventricle.

What does the term “cerebellum” mean in Latin?

The term cerebellum means “little brain” in Latin.

What structure covers the cerebellum?

The cerebellum is covered by the tentorium cerebelli.

How is the cerebellum connected to the brain stem?

The cerebellum is connected to the brain stem by three cerebellar peduncles.

What is the weight ratio between the cerebellum and cerebrum in adults?

In adults, the weight ratio between the cerebellum and cerebrum is 1:10.

What is the weight ratio between the cerebellum and cerebrum in infants?

In infants, the weight ratio between the cerebellum and cerebrum is 1:20.

What are the major external parts of the cerebellum?

The cerebellum consists of two large lateral hemispheres united by a midline vermis.

Why does the cerebellum appear laminated?

The cerebellar surface is divided by numerous curved transverse fissures, giving it a laminated appearance.

What is the horizontal fissure of the cerebellum?

The horizontal fissure is a conspicuous fissure extending around the dorsolateral border of each hemisphere from the middle cerebellar peduncle to the vallecula, separating the superior and inferior surfaces.

What is the deepest fissure in the vermis?

The primary fissure is the deepest fissure in the vermis.

What does the primary fissure divide?

The primary fissure divides the cerebellum into anterior and posterior lobes.

What is the vermis of the cerebellum?

The vermis is the medial cortico-nuclear zone of the cerebellum located in the posterior cranial fossa.

What does the word “vermis” mean in Latin?

Vermis means “worm” in Latin.

What is the functional role of the cerebellar vermis?

Functionally, the vermis is associated with bodily posture and locomotion.

How are the cerebellar hemispheres divided?

Each cerebellar hemisphere consists of lobes separated by deep and distinct fissures.

What functions do the anterior and posterior lobes of the cerebellum govern?

The anterior and posterior lobes govern subconscious aspects of skeletal muscle movements.

What is the function of the flocculonodular lobe?

The flocculonodular lobe contributes to equilibrium and balance.

What are the four deep cerebellar nuclei?

The four deep cerebellar nuclei are the dentate, emboliform, globose, and fastigial nuclei.

What is the dentate nucleus?

The dentate nucleus is the largest deep cerebellar nucleus located within the white matter of each cerebellar hemisphere.

Why is the dentate nucleus called “dentate”?

The dentate nucleus has a tooth-like or serrated edge.

What is the major function of the dentate nucleus?

The dentate nucleus is the major structure linking the cerebellum to the rest of the brain.

Where is the emboliform nucleus located?

The emboliform nucleus lies medial to the dentate nucleus and partly covers its hilum.

What is another name for the emboliform nucleus?

The emboliform nucleus is also called the anterior interposed nucleus.

Where is the fastigial nucleus located?

The fastigial nucleus is located near the midline at the anterior end of the superior vermis above the roof of the fourth ventricle.

What type of tissue forms the fastigial nucleus?

The fastigial nucleus is gray matter embedded in the white matter of the cerebellum.

Where is the globose nucleus located?

The globose nucleus lies medial to the emboliform nucleus and lateral to the fastigial nucleus.

What types of neurons are found in the globose nucleus?

The globose nucleus contains primarily large and small multipolar neurons.

What is the arbor vitae cerebelli?

The arbor vitae is the tree-like white matter of the cerebellum.

Why is the arbor vitae called the “tree of life”?

It is called the tree of life because of its tree-like appearance.

What is the function of the arbor vitae?

The arbor vitae carries sensory and motor information to and from the cerebellum.

What are cerebellar peduncles?

Cerebellar peduncles are bundles of white matter connecting the cerebellum to the brain stem.

What does the superior cerebellar peduncle connect?

The superior cerebellar peduncle connects the cerebellum to the midbrain.

What does the middle cerebellar peduncle connect?

The middle cerebellar peduncle connects the cerebellum to the pons.

What type of fibers compose the middle cerebellar peduncle?

The middle cerebellar peduncle is composed entirely of centripetal fibers (sensory)

What does the inferior cerebellar peduncle connect?

The inferior cerebellar peduncle connects the cerebellum to the medulla oblongata.

What are the anatomical lobes of the cerebellum?

The anatomical lobes are the anterior lobe, posterior lobe, and flocculonodular lobe.

What is the archicerebellum?

The archicerebellum is the vestibular part of the cerebellum formed by the flocculonodular lobe and associated fastigial nuclei.

Where is the archicerebellum located?

The archicerebellum lies on the inferior surface in front of the posterolateral fissure.

What is the embryological significance of the archicerebellum?

The archicerebellum is the oldest embryological part of the cerebellum.

What type of afferent fibers does the archicerebellum receive?

The archicerebellum receives vestibular afferent fibers from the vestibular apparatus of the inner ear via vestibulocerebellar tracts.

What is the primary function of the archicerebellum?

The archicerebellum is concerned with equilibrium.

What structures connect with the archicerebellum through the inferior cerebellar peduncle?

The vestibular and reticular nuclei connect with the archicerebellum through the inferior cerebellar peduncle.

Where do vestibular afferent fibers terminate in the cerebellum?

Vestibular afferent fibers terminate in the cortex of the ipsilateral flocculonodular lobe.

Where do Purkinje cell efferents from the archicerebellum project?

Purkinje cell efferents project to the fastigial nucleus.

Where does the fastigial nucleus project?

The fastigial nucleus projects to the vestibular nuclei and reticular formation.

How does the archicerebellum influence the locomotor system?

It influences the locomotor system bilaterally through descending vestibulospinal and reticulospinal tracts.

What are the subdivisions of the archicerebellum vermis?

The vermis subdivision is the nodulus.

What are the hemispheric subdivisions of the archicerebellum?

Paraflocculus and flocculus.

What is the paleocerebellum?

The paleocerebellum is the spinal part of the cerebellum formed by the vermis, paravermis, globose nucleus, and emboliform nucleus

(anterior lobe)

What type of sensory input does the paleocerebellum receive?

The paleocerebellum receives proprioceptive impulses from muscles and tendons mainly through dorsal and ventral spinocerebellar tracts.

What is the primary function of the paleocerebellum?

The paleocerebellum is concerned with muscle tone and posture.

Where does the paleocerebellum send efferent fibers?

The paleocerebellum sends efferent fibers to the red nucleus of the midbrain.

What gives the red nucleus its reddish color?

The red nucleus appears pale pink due to iron present as hemoglobin and ferritin.

What receptors contribute to spinal afferents to the paleocerebellum?

Muscle, joint, and cutaneous receptors contribute spinal afferents.

Through which peduncles do spinocerebellar afferents enter the cerebellum?

Spinocerebellar afferents enter through the inferior and superior cerebellar peduncles.

Where do cortical efferent fibers of the paleocerebellum terminate?

They terminate in the globose and emboliform nuclei.

Through which peduncle do paleocerebellar efferents travel?

They travel through the superior cerebellar peduncle.

What descending tract arises from the red nucleus in the paleocerebellar pathway?

The rubrospinal tract arises from the red nucleus.

What are the vermis subdivisions of the paleocerebellum (anterior lobe)?

The vermis subdivisions are the lingula and culmen.

What hemispheric structures belong to the paleocerebellum (anterior lobe)

The central lobule and anterior quadrangular lobule belong to the paleocerebellum.

What is the neocerebellum?

The neocerebellum is the cerebral part and largest portion of the cerebellum (posterior lobe)

What structures form the neocerebellum?

The neocerebellum consists mainly of the cerebellar hemispheres and dentate nuclei.

What type of afferent input does the neocerebellum receive?

The neocerebellum receives afferent impulses from the cerebral cortex and pons via the cerebro-ponto-cerebellar pathway.

What is the major function of the neocerebellum?

The neocerebellum controls voluntary muscle coordination.

To which thalamic nucleus does the neocerebellum send efferents?

The neocerebellum sends efferents to the ventrolateral nucleus of the thalamus.

What role does the neocerebellum play in movement?

The neocerebellum is involved in muscular coordination and movement planning.

Describe the cerebro-ponto-cerebellar tract.

Signals from the cerebral cortex go to pontine nuclei, cross to the opposite side, and enter the cerebellum through the middle cerebellar peduncle.

Where do neocerebellar efferents project first?

They project first to the dentate nucleus.

Where does the dentate nucleus project?

The dentate nucleus projects to the contralateral red nucleus and ventrolateral thalamic nucleus.

What descending pathways are ultimately influenced by the neocerebellum?

The corticospinal and corticobulbar tracts are influenced by the neocerebellum.

What forms a major part of the superior cerebellar peduncle?

Efferents from the dentate nucleus form a major part of the superior cerebellar peduncle.

What are the vermis subdivisions of the neocerebellum?

The vermis subdivisions are the declive, folium, tuber, pyramis, and uvula.

What hemispheric structures belong to the neocerebellum?

The simple lobule, superior semilunar lobule, gracile lobule, biventral lobule, and tonsil belong to the neocerebellum.

What are the three layers of the cerebellar cortex?

The cerebellar cortex consists of the molecular layer, Purkinje cell layer, and granular layer.

What cells are found in the molecular layer?

The molecular layer contains stellate cells, basket cells, parallel fibers, and Purkinje cell dendrites.

What neurotransmitter do stellate cells use?

Stellate cells use taurine as an inhibitory neurotransmitter.

What are the afferent and efferent connections of stellate cells?

Stellate cells receive afferents from parallel fibers and send efferents to Purkinje cell dendrites.

What neurotransmitter do basket cells use?

Basket cells use GABA as an inhibitory neurotransmitter.

What is the function of basket cells?

Basket cells inhibit or reduce the activity of neurons.

What are the afferent and efferent connections of basket cells?

Basket cells receive afferents from parallel fibers and send efferents to the Purkinje cell soma.

What are parallel fibers?

Parallel fibers are axons of granule cells.

How many Purkinje cells are present in the cerebellum?

Approximately 15 million Purkinje cells are present.

What neurotransmitter do Purkinje cells use?

Purkinje cells use GABA as an inhibitory neurotransmitter.

What afferent inputs do Purkinje cells receive?

Purkinje cells receive input from parallel fibers, climbing fibers, stellate cells, and basket cells.

Where do Purkinje cell efferents project?

Purkinje cell efferents project to the deep cerebellar nuclei.

What is Bergmann’s glial cell?

Bergmann’s glial cells are specialized astrocytes found exclusively in the cerebellar cortex.

Describe the morphology of Purkinje cells.

Purkinje cells are flask-shaped, single-layered neurons with profusely branching dendrites covered in dendritic spines.

Where do Purkinje cell dendrites extend?

Purkinje cell dendrites extend into the molecular layer.

Where do Purkinje cell axons synapse?

Purkinje cell axons synapse with deep cerebellar nuclei, basket cells, stellate cells, and vestibular nuclei.

How many granule cells are present in the cerebellum?

Approximately 50 billion granule cells are present.

What neurotransmitter do granule cells use?

Granule cells use glutamic acid as an excitatory neurotransmitter.

What input do granule cells receive?

Granule cells receive afferent input from mossy fibers.

What structures do granule cells influence?

Granule cells influence Purkinje cells, basket cells, and stellate cells.

What neurotransmitter do Golgi cells use?

Golgi cells use GABA as an inhibitory neurotransmitter.

What inputs do Golgi cells receive?

Golgi cells receive afferent input from parallel fibers and mossy fiber rosettes.

What is the efferent target of Golgi cells?

Golgi cells project to granule cell dendrites.

Where do climbing fibers originate?

Climbing fibers originate from the inferior olivary complex.

How do climbing fibers affect Purkinje cells?

Climbing fibers exert a direct, powerful, and sharply localized action on individual Purkinje cells.

What role do basket, stellate, and Golgi cells play in the cerebellum?

They act as inhibitory interneurons.

Where do mossy fibers originate?

Mossy fibers originate from the spinal cord and brain stem centers.