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Divisions (anatomical)

  1. It has a central vermis (made up of 10 lobules)
  2. 2 lateral cerebellar hemispheres- these have many foldings and therefore have a large surface area.

The 10 lobules of the vermis are:

I            : Lingula

II & III   : Centralis

IV & V   : culmen

VI         : Lobulus simplex

VII        : Folium, tuber

VIII       : Pyramis

IX          : uvula

X           : Nodulus


Functional divisions

  1. Spinocerebellum
  2. Cerebrocerebellum (or neocerebellum)
  3. Vestibulocerebellum  

  1. To medial descending systems for motor execution
  2. To lateral descending system
  3. To motor and premotor cortex – for motor planning
  4. To vestibular nuclei – for balance and eye movements  

The constituents of 3 parts of the cerebellum are:






Vermis (except the nodulus ) and the adjacent medial portions of the hemispheres


Proprioceptive input from body

Copy of the motor plan



From vermis


Brains stem area (for axial and proximal limb muscles)

From the hemispheres


brain stem area ( For distal muscles)

By comparing plan with

performance, it smoothens and coordinates movements

Cerebro cerebellum (or neocerebellum)

The lateral portions of hemispheres

Intract with motor cortex

Planning and programming movements

Vestibulo cerebellum (or the floculo- nodular lobe)

The nodulus and flocculus



Learning induced change in vestibulo ocular reflex.



The cerebellum is organized as:                 

  1. An outer cerebellum cortex, separated by
  2. White matter from the
  3. Deep cerebellar nuclear


The cerebellar cortex has 3 layers and 5 types of cells :

The 3 layers are:

  1. The outer molecular
  2. Middle purkinje     
  3. Inner granular

The 5 cells are:

  1. Purkinje    
  2. Granular   
  3. Golgi                
  4. Stellate    
  5. Basket


Location of the cell bodies of the cells:

Stellate, Basket : Outer molecular layers

Purkinje : Middle Purkinje layer
Golgi, Granular : Inner granular

(also, the ‘glomeruli’ lie in the inner granular)


The deep nuclei are (4 on each side)

  • Dentate
  • Emboliform
  • Fastigial
  • Globose

(the emboliform and globose are together referred to as the Inter positus)



1.  Afferent

There are 2 main primary afferent inputs:

a.  Mossy fibres

b.  Climbing fibres 

  1. Both of these are excitatory; they send collateral to the deep nuclei & pass to the cerebellar cortex.
  2. The climbing fibres ends on the Purkinje cell; the mossy fibres also end on the Purkinje cell, but through the granule cell.
  3. The input to the Purkinje cell from the climbing fibre is 1:1; it is a stong excitatory input and produces a complex spike whereas the input to the Purkinje cell from the mossy fibre is 1 million : 1; it is a weak input and produces a simple spike.
  4. What do the mossy and climbing fibres convey?
  5. Climbing Fibres = They come from one single source viz the inferior olivary nuclei. The climbing fibres convey proprioceptive inputs from all over the body


Mossy fibres: They come from many sources. The fibres first end on the dendrites of the granule cells in “glomeruli”. The mossy fibres conveys proprioceptive input from all parts of the body and also input from the cerebral cortex via pontine nuclei to the cerebellar cortex.


The various tracts carried by the climbing and mossy fibres are:

1. Vestibulo- cerebellar

Vestibular impulses from labyrinth.

Direct and via vestibular nuclei (Ipsilateral)

 2. Dorsal spinocerebellar

Proprioceptive and exteroceptive impulses from body (trunk/ leg) (Ipsilateral)

3. Ventral spinocerebellar

Proprioceptive and exteroceptive impulses from body (trunk/ leg) (Contralateral)

4. Cuneo cerebellar

Proprioceptive impulses from head and neck (Ipsilateral)

5. Olivo cerebellar

Proprioceptive impulses from all over body through relay in inferior olive

6. Tecto – Cerebellar

Auditory and visual impulses via inferior and superior colliculi

7. Ponto- cerebellar

Impulses from motor and other parts of cerebral cortex via pontine nuclei (From Opposite cerebral cortex)

8. Rubro- cerebellar

Impulses from opposite red. Nucleus

9. Reticulo- cerebellar

Impulses from brain stem reticular formation

  • The olivo cerebellar pathway projects to cerebellar cortex via climbing fibres.
  • The rest of the listed pathways project via mossy fibres.

[The sensory input to the cerebellum is mostly ipsilateral]

[The dentatethalamo– cortical pathway crosses to the opposite side; further; the corticospinal tract also crosses to the opposite side. Therefore, the cerebellum regulates the activity of the SAME side of the body. In cerebellar lesions, there is a in muscle tone on the same side and the patient tends to fall on same side.]

Efferent (output) cerebellum

  1. From vestibulo cerebellum – directly to the brain stem (not via the deep nuclei)
  2. From spinocerebellum



(Note that only the output from the vestibulo cerebellum does not go via the deep nuclei)


Vestibulo-Cerebellum                Rest of the cerebellum

Cerebellar cortex

Deep nuclei

(Cerebellar output)

Direct (to brainstem) Via the deep nuclei (to brainstem/ thealamus)


NOTE: the afferent inputs go both to the cerebellar cortex and to the deep nuclei. In other words, deep nuclei receive input from the cerebellar cortex (except vestibulocerebellum) as well (as via the collateral) from the afferent inputs of the cerebellum


3.  Inside connections

Purkinje cell: (recall that the climbing fibres end directly on the Purkinje cell; the mossy fibres end on the Purkinje cell through the granular cell.) The Purkinje cell projects to the deep nuclei; the deep nuclei then gives its output out of the cerebellum. The input from the Purkinje cell to the deep nuclei is inhibitory; however, the deep nuclei output is always excitatory. Even at rest deep nuclei continuously discharge excitatory inputs. When movement occurs, the deep nuclei discharge increase at first; within a few milliseconds, inhibition of this discharge occurs by the Purkinje cell. This allows damping.


Output from deep nuclei is always excitatory.


Granule cell: Output from the granule cell axons bifurcate and give rise to parallel fibres. The granule cell stimulates the Purkinje cell; however, the granule cell also ends at basket/ stellate cells and stimulates them. But the basket and stellate cells in turn inhibit the Purkinje cell (this inhibition by the basket/ stellate cell is an example of feed forward inhibition). The granule cell itself is inhibited by the Golgi cell




The granule cell synthesizes glutamate but has GABA receptor on it. The Golgi cell inhibits granule cell via the GABA receptors.


NOTE: Out of the 5 cells in the cerebellar cortex only the output from the granule cell is excitatory the output from the rest of the cells is inhibitory.



a. Granule cell

Stimulates the Purkinje, Basket and stellate cells

b. Purkinje cell

Inhibits deep nuclei

c. Golgi cell

Inhibits granule cell

d. Basket cell

Inhibits Purkinje cell

e. Stellate cell

Inhibits Purkinje cell


Thus, the overall circuitry can be summarized as follows:


(Note: the synaptic connections in the granule cell from the ‘glomeruli’)



a.  Maintenance of equilibrium – this is the function of the vestibulo cerebellum (i.e. the flocculonodular lobe). There is inter connection between the vestibular apparatus and the flocculonodular lobe.

Role in regulation of tone/ posture – the effects of the cerebellum on the stretch reflex are complex. With cerebellar disease one would expect an increased in tone. But in humans, hypotonia occurs in cerebellar disease. The spinocerebellum projects on:

  1.  The alpha motor neurons (through efferent output to vestibular nuclei)
  2. The gamma motor neurons (through efferent output to reticular formation)
    There is a perfect co ordination between the alpha and gamma motor neuron discharge (the alpha-  gamma linkage).
  3. The linkage exists at the level of the spinal cord; the ‘switch’ for the linkage is in the cerebellum.
  4. Error control function / effects on movement- By comparing plan with performance, (the cerebellum gets input from the cortex as well as various sensory inputs) the cerebellum makes anticipatory corrections.
  5. Planning functions – This is the function of the neocerebellum

Role in learning: The cerebellum is concerned with learned adjustments to repetitive tasks.


5.  Cerebellar lesions/ disease


  • No paralysis
  • No sensory deficit
  • No abnormalities at rest (except the changes in stretch reflexes)
  • Ataxia (drunken gait)
  • Slurred/ scanning speech
  • Dysmetria (past- pointing)
  • Intention tremor
  • Rebound phenomenon
  • Adiadokodinesia
  • Decomposition of movement

[Electrical activity in cerebellum: the basic electrical of frequency rhythm of the cerebellar cortex is of frequency 150- 300/ S and 200v amplitude. Superimposed on this basic rhythm is a 1000-2000/s component of smaller amplitude.]


Upper motor neuron lesions  

Lower motor neuron lesions

Paralysis of movements rather than muscles

Individual muscle or muscle group affected

Slight disuse atrophy

Marked wasting



Clasp knife spasticity

Flaccid paralysis

Tendon reflexes increased (clonus may be present)

Tendon reflexes decreased or absent

Positive Babinski sign

Negative Babinski sign



Circadian rhythm is controlled by (AIIMS Nov 08)

  1. Supraoptic nucleus
  2. Suprachiasmatic nucleus
  3. Paraventricular nucleus
  4. Median eminence

B. Suprachiasmatic nucleus

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