Anatomy of the Cerebellum

Question 1

What is the cerebellum?

Answer 1

motor part of the brain

Question 2

What are the functions of the cerebellum?

Answer 2

1. Maintain equilibrium
2. Posture control
3. Coordinate muscle contraction in both stereotype and non-stereotype (voluntary movements)

Question 3

What is the location of the cerebellum?

Answer 3

• Located on the lower part of the posterior cranial fossa.
• Separated from the occipital lobe by tentorium cerebelli
• Lies behind the posterior aspect of the pons and medulla
• Forms the roof of the 4th ventricle

Question 4

Describe the structure of the cerebellum?

Answer 4

1. Two cerebellar hemispheres (left and right)
2. The central part called vermis unites the hemispheres
   - The surfaces bears curved fissures between narrow folds called folia

Question 5

Describe the 2 important fissures of the cerebellum?

Answer 5

1. Primary fissure (on superior surface) – divides it into:
   - Anterior lobe
   - Posterior lobe
2. Posterolateral fissure (on inferior surface) – separate floccularnodular lobe from the body of the cerebellum (corpus cerebelli)

Question 6

What is the vermis of the cerebellum?

Answer 6

an unpaired medial structure that separates the cerebellar hemispheres

Question 7

Describe the structure of the vermis?

Answer 7

1. Superior vermis – slight ridge extends anteriorly to include the lingula of medullary vellum
2. Inferior vermis – clearly demarcated by valleculla cerebelli
   - Antero-posteriorly divided into:
   > Nodule - extends a stalk to the flocculus forming flocculonodular lobe
   > Uvula
   > Pyramid

Question 8

What is the tonsil of the cerebellum?

Answer 8

partially separated lobule that over hangs the inferior vermis

Question 9

Describe the lobes of the cerebellum?

Answer 9

1. Anterior lobe – marked behind by the primary fissure
2. Posterior lobe – remainder of hemispheres + uvula + pyramid
3. Flocculonodular lobe – nodue + flocculum

Question 10

Name the 10 lobules of the cerebellum?

Answer 10

Lingula, Central, Culmen, Declive, Folium, Tuber, Pyramis, UvulaTonsil, Flocculonodular

Question 11

What is the archcerebellum?

Answer 11

• First to develop with the vestibular nuclei
• Well developed in fish
• In humans, represented by:
  1. Flocculonodular lobe + lingula
  2. Vestibular system
• Involved in mechanisms of balance (equilibration)

Question 12

What is the paleocerebellum?

Answer 12

• second to develop
• Well developed in terrestrial vertebrates –reptiles
• In humans, represented by:
  1. Anterior lobe
  2. Anterior and posterior vermis
• Connect to spinal cord through motor neurons for muscle tones

Question 13

What is the neocerebellum (posterior lobe)?

Answer 13

• Last to develop
• Well developed in humans
• Controls non-stereotyped, skilled learned activities

Question 14

What are the cerebellar peduncles?

Answer 14

• Connects the cerebellum to the brainstem (medulla, pons and midbrain)
• convey inputs and outputs from parts of the body to cerebellar cortex

Question 15

Name the cerebellar peduncles?

Answer 15

1. Superior peduncle (brachium conjuctivum)
2. Middle peduncle (brachium pontis)
3. Inferior peduncle (restiform body)

Question 16

Describe the superior peduncle?

Answer 16

• Connects the cerebellum to the junction of the pons and the midbrain
• Contains both afferent and efferent fibers
  > to red nucleus and thalamus
• efferent fibers leave the cerebellum to the thalamus and spinal cord
• they normally relay to red nucleus at the level of the superior colliculus

Question 17

Describe the middle cerebellar peduncle?

Answer 17

• Connects the cerebellum to the pons
• Contains afferent fibers from pontine nuclei of contralateral side
• Involves fibers from contralateral pons to cerebellum

Question 18

Describe the inferior cerebellar peduncle?

Answer 18

• connects the cerebellum to the medulla oblongata
• carries both afferent and efferent fibers
• carries fibers from spinal cord (spinocerebellar fibers), medulla oblongata (cuneocerebellar -from nucleus cuneatus), reticular formation (reticuocerebellar fibers) to cerebellum.
• Carries climbing fibers from the inferior olivary nucleus to cerebellum

Question 19

Describe the components of the cerebellum?

Answer 19

1. Cortex or Surface layer (gray matter)
   - contained in transverse folds or folia
   - Detailed structure is uniform throughout
2. Medullary center (white matter)
   - contains four pairs of deep intracerebellar nuclei:
   - Nuclei lie in the roof of 4th ventricle – hence called roof nuclei

Question 20

What are the deep cerebellar nuclei?

Answer 20

• Buried in medullary center of each hemisphere.
• These nuclei are ( from medial to lateral):
  1. Fastigial nucleus
  2. globose nucleus
  3. emboliform nucleus
  4. the dentate nucleus

Question 21

Describe the fastigial nucleus of the deep cerebellar nuclei?

Answer 21

• Lie close to midline on the anterior surface of the superior vermis
• Well developed in fish
• Controls the functions of the arch cerebellum

Question 22

Describe the globose nucleus of the deep cerebellar nuclei?

Answer 22

• Lies on lateral side of the fastigial but medial to emboliform nucleus
• control the functions of the paleocerebellum

Question 23

Describe the emboliform nucleus of the deep cerebellar nuclei?

Answer 23

• Lies on the medial side of the dentate
• control the functions of the paleocerebellum

Question 24

Describe the dentate nucleus of the deep cerebellar nuclei?

Answer 24

• occupies the center of the cerebellar hemispheres
• Has a hilum that faces medially
• Well developed in humans
• Controls the functions of the neocerebellum

Question 25

Describe the cerebellar cortex?

Answer 25

Is a uniform three – layered structure:
1. molecular layer
2. purkinje layer
3. granular layer

Question 26

Describe the molecular layer of the cerebral cortex?

Answer 26

Consists of axons and dendrites of various cerebellar neurons.
Made up of sublayers:
> stellate cell layer ( scattering stellates outermost + modified stellate cells called basket cells) (outermost)

Question 27

Describe the Purkinje fibers layer of the cerebellar cortex?

Answer 27

• Made up of purkinje cells their dendrites ramify the molecular layer
• climbing fibers synapse with dendrites of purkinje fibers in the molecular layer

Question 28

Describe Purkinje cells?

Question 29

Describe the contents of the granular layer of the cerebellar cortex?

Answer 29

1. granular cells
   their short denrites synapse with mossy-fibers forming glomeri
   their axons synapse in the molecular layer
   axons divide in T-shape to form parallel fibers
2. golgi cells are scattered among granular cells form glomerulus
3. Golgi cells: receive input from mossy and parallel fibers, and inhibit the mossy fiber to granule cellls synapses, thus modulating the signal on the parallel fibers.
4. basket cells: receive input from and inhibit the Purkinje cells, providing a kind of gain control. Long range, offbeam inhibition.
5. Stellate cells: apparently the same function as basket cells. Short range inhibition
6. Lugaro cells receive input from 5 -15 Purkinje cells and project to basket, stellate, and Golgi cells.
7. Unipolar brush cells. Excitatory interneurons using glutamate as the neurotransmitter

Question 30

Describe the 3 types of nerve fibers in the white matter of the cerebellum?

Question 31

Describe the white matter of the cerebellum?

Answer 31

• Fibers from peduncles enter the white matter.
• Thin lamina of white matter join the two sides
• Thin lamina divide white matter into:
  1. superior medullary velum
  2. inferior medullary velum

Question 32

The white matter of the cerebellum is made up of?

Answer 32

1. afferent fibers from outside the cerebellum
2. projection fibers from the cerebellar cortex to cerebellar nuclei
3. Association fibers that connect different parts of the cerebellar cortex
4. commissural fibers that connect the two cerebellar hemispheres
5. fibers from cerebellar nuclei +cortex to centers outside the cerebellum

Question 33

Describe the intrinsic pathway of the cerebellum?

Question 34

Describe the cerebellar afferent pathway?