Fine structure of the cerebellum

Question 1

I. Structure of the cerebellum
1. What is the general structure of the cerebellum?

Answer 1

• Built up of folia on the outside which increase the
  surface area
• There are 3 lobes, anterior lobe, posterior lobe and flocculonodular lobe
• We have 4 nuclei in the section of the cerebellum: Dentate, Emboliform, Globose and Fastigial
  nucleus. (Don’t Eat Greasy Food)
• The 3 cerebellar peduncles connect the cerebellum
  to the brainstem:
  1. Inferior cerebellar peduncle – medulla
  2. Middle cerebellar peduncle – pons
  3. Superior cerebellar peduncle – mesencephalon

Question 2

I. Structure of the cerebellum
2. What are the 4 nuclei in the cerebellum?

Answer 2

We have 4 nuclei in the section of the cerebellum.
Dentate, Emboliform, Globose and Fastigial nucleus. (Don’t Eat Greasy Food)

Question 3

I. Structure of the cerebellum
3. What are the 3 cerebral peduncles in the cerebellum?

Answer 3

1. Inferior cerebellar peduncle – medulla
2. Middle cerebellar peduncle – pons
3. Superior cerebellar peduncle – mesencephalon

Question 4

II. Functional anatomy
1. What are the characteristics of vestibulocerebellum?

Answer 4

• The vestibulocerebellum, comprising the flocculus and nodulus.
• Receives input from the vestibular nuclei.
• Regulates equilibrium and balance

Question 5

II. Functional anatomy
2. What are the characteristics of Spinocerebellum (paleocerebellum) ?

Answer 5

• Spinocerebellum (paleocerebellum) comprises the vermis and paravermal area (intermediate zone).
• Receives input directly from the spinal cord (proprioception).
• Regulates movements and muscle tone

Question 6

II. Functional anatomy
3. What are the characteristics of Cerebrocerebellum (neocerebellum)?

Answer 6

Cerebrocerebellum (neocerebellum) occupies most of the lateral cerebral hemispheres and receive input from many areas of the cerebral cortex.

Related to regulation of highly skilled movements, planning and execution of movements, muscle memory

Question 7

III. Layers of the cerebral cortex
1. What are the 3 layers of cerebral cortex?

Answer 7

The cortex of the cerebellum has 3 layers: an inner granular layer, Purkinje cell layer (ganglionic layer) and the outer molecular layer.
( Inside the cortex, we have a central white matter core, where axons enter and leave the cortex can be found.)

Question 8

III. Layers of the cerebral cortex
2. What are the characteristics of granular layer?

Answer 8

Granular cell layer contains billions of granule cells and Golgi cells

Question 9

III. Layers of the cerebral cortex
5. Which cells are inhibitory cells? Which cells are excitatory cells?

Answer 9

Inhibitory
- Golgi cells
- Basket cells and Stellate cells
- Purkinje cells

Excitatory cells: granule cell

Question 10

III. Layers of the cerebral cortex
4. What are the characteristics of Purkinje layer?

Answer 10

• Purkinje layer contains Purkinje cells

Question 11

III. Layers of the cerebral cortex
5. What are the characteristics of Purkinje cell?

Answer 11

• Largest neurons in the CNS
• Cell bodies are pear shaped. The dendritic tree start as 2-3 main branches and
  ramify further into fine arborizations forming the dendritic tree. They are restricted to the sagittal plane, which is perpendicular to the longitudinal axis of the cerebellar folium
• Purkinje cell axons project primarily to the cerebellar nuclei, but a few exit the cerebellum and terminate directly on the vestibular nuclei
• Purkinje cell axons are the only exit for information leaving the cerebellar cortex

Question 12

III. Layers of the cerebral cortex
6. What are the characteristics of Granule cell?

Answer 12

• Small perikaryon and is found
  densely in the granular layer
• 3-4 dendrites with claw-like
  projections at their terminal end
• The thin axon is sent to the
  molecular layer where it
  bifurcates and run parallel to the
  folium.
• The parallel fibers are
  unmyelinated and extend up to
  1mm and make excitatory synapses with the dendrites of Purkinje cells.
• Each Purkinje cell receive synaptic contact from about 200 000 parallel fibers

Question 13

III. Layers of the cerebral cortex
7. What are the characteristics of Basket + stellate cells?

Answer 13

• Basket cells and stellate cells are interneurons in the molecular layer, both being inhibitory
• Basket cell axons arborize in the molecular and Purkinje layers and surround the perikarya (in a basket like manner) of the adjacent 5-8 Purkinje cells
• Axons of stellate cells terminate on dendrites of Purkinje cells

Question 14

III. Layers of the cerebral cortex
8. What are the characteristics of Golgi cells?

Answer 14

• Larger than the granule cell and scattered in the granular layer
• The dendritic tree ramify in the molecular layer and are spread in all directions
  (not flattened like for Purkinje cells)
• The axons branch a lot in the granular layer and synapse with a large number of granule cells, forming a negative feed-back loop

Question 15

III. Layers of the cerebral cortex
9. What are the characteristics of Glomerular synapses?

Answer 15

• The granular layer contains small cell-free islets, called
  glomeruli
• Dendritic endings of granule cells form synaptic contact
  with the axon terminals of afferent nerve fibers,
  especially by mossy fibers
• Short axon of Golgi cells terminate here
• This large synapse (glomerular synapse) is enveloped by
  glial processes

Question 16

III. Layers of the cerebral cortex
10. What are the characteristics of Glial cells of the cortex of cerebellum?

Answer 16

• We can find normal glial cells, like the oligodendrocytes and astrocytes
• Also have special glial cells like Bergmann glia and Fananas glia
• Bergmann glia have their cell body between the Purkinje cells and long supporting fibers towards the surface. The Bergmann glia start to proliferate where the Purkinje cells die

Question 17

III. Layers of the cerebral cortex - Intracortical circuit
11A. What are the 2 different types of terminals enter into the cortex?

Answer 17

The climbing fibers and the mossy fibers

Question 18

III. Layers of the cerebral cortex - Intracortical circuit
11B. What are the characteristics of The climbing fibers?

Answer 18

• Climbing fibers terminate on Purkinje cells by splitting up and synapsing with the dendritic tree of a single Purkinje cell (1 climbing fiber goes to a single Purkinje cell). Via axon collaterals also on some stellate and basket cells
• Climbing fibers originate from neurons of the inferior olive and its accessory nuclei

Question 19

III. Layers of the cerebral cortex - Intracortical circuit
11C. What are the characteristics of The mossy fibers?

Answer 19

• Mossy fibers divide into branches and give off small lateral branches which synapse with granule cell dendrites, forming
  the glomerular synapse
• Mossy fibers originate from spinocerebellar and pontocerebellar tract and nuclei of the medulla

Question 20

III. Layers of the cerebral cortex - Intracortical circuit
11D. What happen When granule cell gets excited?

Answer 20

• When granule cell gets excited, they excite a row of dendrites of the Purkinje cells, which again excite the basket cells.
• Basket cells have a inhibitory effect on the 5- 8 Purkinje cells they surround, which is found laterally of the excited rows of Purkinje cells.

Question 21

III. Layers of the cerebral cortex - Intracortical circuit
11F. What happen when the axons of Purkinje cells terminate on neurons of cerebellar nuclei as inhibitory neurons (GABA)?

Answer 21

• Cerebellar nuclei also receive excitatory input via axon collaterals from mossy fibers and climbing fibers. However, these cannot be passed on further as there is inhibitory control from the Purkinje cells
• Only when the Purkinje cells are inhibited by inhibitory interneurons like basket cells, stellate cells and Golgi cells, the excitatory impulses can be passed on