Anatomy of cerebellum, internal and external structure

2.  Latin for ‘little brain’
 Largest part of hindbrain
 Occupies most of posterior cranial fossa
 Lies behind pons & medulla
 forming roof of 4th ventricle
 Separated from posterior part of cerebrum
 by tentorium cerebelli

4. Connection with the brainstem
 Superior Cerebellar
Peduncle
(brachium conjunctivum)
 Connects with midbrain
 Middle Cerebellar Peduncle
(brachium pontis)
 Connects with pons
 Inferior Cerebellar
Peduncle (restiform body)
 Connects with medulla

5.  Two cerebellar hemispheres .
 Median vermis.
 Two surfaces ----superior and
inferior
 3 fissures:
 fissura prima,
 horizontal fissure and
 posterolateral fissure
 3 lobes in each hemisphere
 anterior ,
 posterior and
 flocculonodular.

6. Flattened view of the cerebellar cortex
showing the main cerebellar lobes, lobules,
and fissures. B: Relationship between the
diagram in (A) and the cerebellum.
(courtesy- Snell’s clinical neuroanatomy)

7. Functional and phylogenetic subdivision
Regulation of
muscle tone,
coordination of
skilled voluntary
movement
Planning of
voluntary activity/
modulation of
motor skills
Maintenance of
balance, control
of eye movements
Vestibulocerebellum/Archicerebellum
Spinocerebellum/Paleocerebellum
Cerebrocerebelum/neocerebellum
Anterior Lobe
Posterior
Lobe
Flocculo-Nodular
Lobe (FN lobe)
Primary fissure

8. Internal structure
 Outer gray matter called cerebral cortex, extensivly
folded forming folia
 Inner white matter, showing distinctive treelike
pattern called Arbor vitae (tree of life)
 4 pairs of nuclei within white matter ,the deep cerebral
nuclei

9. The cerebral cortex
 Microscopically composed of three
layers:
 Outer molecular
 Middle ,Purkinje cell layer and
 Inner , Granule cell layer
 Contains five types of neurons:
 Basket cell
 Stellate cells
 Pukinje cell – Purkinje cell layer
 Granule cell &
 Golgi cell
 Purkinje cell axons, are the only
output from the cerebellar cortex,
to the deep nuclei
Molecular layer
Granule cell layer

10. Basket made
By axon of
Basket cell
Basket Cell
basket on
Purkinje cell

11. Inputs:
• Climbing fiber (“+”, excitatory,
from inferior olive nucleus)
• Mossy fiber (+, excitatory,from
spinal cord & brain stem)
Output:
• Purkinje cell axon (“-”, inhibitory)
Input and output of the cerebral cortex

12. The Afferent Cerebellar Pathways
Afferent Tracts Transmits Destination
Dorsal spinocerebellar Unconscious kinesthetic &
cutaneous afferents from trunk &
leg
Anterior lobe,pyramis,uvula &
paramedian lobe via ipsilateral
inferior cerebral peduncle
Ventral Spinocerebellar Exteroceptive and proprioceptive
fibres from body
Vermis and anterior lobe via
ipsilateral superior cerebral
peduncle
Vestibulocerebellar tract Vestibular impulse from labyrinth
direct and via vestibular nuclei
Flocculonodular lobe via ipsilateral
inferior cerebral peduncle
Cuneocerebellar tract Proprioceptive impulses, especially
from arm,head and neck
anterior lobe via ipsilateral inferior
cerebral peduncle
Tectocerebellar Auditory and visual impulses via
inferior and superior colliculi
Lobulus simplex ,declive & tuber via
superior cerebral peduncle
Corticopontocerebellar Impulses from motor and other
parts of cerebral cortex via pontine
nuclei
All parts of cerebellar cortex except
flocculonodular lobe via
contralateral middle cerebellar
peduncle
Olivocerebellar Proprioceptive input from whole
body via relay in inferior olive
All parts of cerebellar cortex via
contralateral inferior cerebral
peduncle

13. The Efferent Cerebellar Pathways
 The entire output of the cerebellar cortex is through the axons of the
Purkinje cells.
 The axons of the Purkinje cells end by synapsing on the neurons of the
deep cerebellar nuclei.
 The axons of the neurons that form the cerebellar nuclei constitute the
efferent outflow from the cerebellum.
 A few Purkinje cell axons pass directly out of the cerebellum to the
lateral vestibular nucleus.
 The efferent fibers from the cerebellum connect with the red nucleus,
thalamus, vestibular complex, and reticular formation

14. The Efferent Cerebellar PathwaysPathway Origin Destination
Globose-emboliform-rubral Globose and
emboliform nuclei
To contralateral red nucleus, then via
crossed rubrospinal tract to ipsilateral
motor neurons in spinal cord
Dentothalamic Dentate nucleus To contralateral ventrolateral nucleus
of thalamus, then to contralateral
motor cerebral cortex; corticospinal
tract crosses midline and controls
ipsilateral motor neurons in spinal
cord
Fastigial vestibular Fastigial nucleus Mainly to ipsilateral and to
contralateral lateral vestibular nuclei;
vestibulospinal tract to ipsilateral
motor neurons in spinal cord
Fastigial reticular Fastigial nucleus To neurons of reticular formation;
reticulospinal tract to ipsilateral motor
neurons to spinal cord

17. Functions
 The nervous system uses the cerebellum to coordinate
motor control functions at three levels, as follows:
1. The vestibulocerebellum. This consists principally of the
small flocculonodular cerebellar lobes and adjacent
portions of the vermis. It provides neural circuits for
most of the body’s equilibrium movements.
2. The spinocerebellum. This consists of most of the vermis
of the posterior and anterior cerebellum plus the adjacent
intermediate zones on both sides of the vermis. It
provides the circuitry for coordinating mainly
movements of the distal portions of the limbs, especially
the hands and fingers.

18. 3. The cerebrocerebellum. This consists of the large lateral zones
of the cerebellar hemispheres, lateral to the intermediate
zones. It receives virtually all its input from the cerebral
motor cortex and adjacent premotor and somatosensory
cortices of the cerebrum.
It transmits its output information in the upward direction back
to the brain, functioning in a feedback manner with the
cerebral cortical sensorimotor system to plan sequential
voluntary body and limb movements, planning these as
much as tenths of a second in advance of the actual
movements. This is called development of “motor imagery”
of movements to be performed.

19. (1) CONTROL OF TONE & POSTURE:
Spino-
cerebellum
Sup. & Inf.
Colliculi
Vesti. Nu.
R.F.
1
2
4
5
6
7
o Mainly function of Spinocerebellum.
CHANGE IN BODY POSTURE
Proprioceptive from Body
2.Cuneo-cerebellar
1.Spino-cerebellar (dor. & Vent.)
REFLEX CORRECTION OF MUSCLE TONE
EASY MAINTANENCE OF NEW POSTURE
3.Tecto-cerebellar (Visual & Auditory)
4.Cereb.-vestibular
5.Cereb.-reticular
6.Vestibulo-spinal
7.Reticulo-spinal
A.H.C.
Functions of the cerebellum

20. (2) CONTROL OF EQUILIBRIUM:
o Mainly function of Vestibulocerebellum.
Vestibulo-
cerebellum
Vestibular
Apparatus
V. N.
1
1
2
3
CHANGE IN HEAD POSITION /
ACCELARATION
Labyrinthine Afferents
1.Vestibulo-cerebellar
REFLEX CORRECTION OF MUSCLE TONE
A.H.C.
MAINTANENCE OF BODY EQUILIBRIUM
2.Cereb.-vestibular 3.Vestibulo-spinal
Function of the cerebellum

21. Functions of the cerebellum
(3) CONTROL OF VOLUNTARY MOVEMENT:
 Act as a “comparator of a servo mechanism”
 Cerebellum receives two types of information
 intended plan of movement (direct information from the motor
cortex)
 what actual movements result (feedback from periphery)
 These two are compared: an error is calculated
 Corrective output signals goes to
 motor cortex via thalamus
 brain stem nuclei and then down to the anterior horn cell through
extrapyramidal tracts

22. Functions of the cerebellum
Corrective Signals through Dentato-
Thalamo-Cortical Fibres
Cortico-Ponto-Cerebellar fibres
Spino-Cerebellar Fibre.

23. Functions of the cerebellum
(4) LEARNING NEW SKILLED VOLUNTARY MOVEMENTS:
 Role of Inferior Olivery Nuclei – Climbing Fibers.
 Each Purkinje cell receives input from a single climbing fiber
 Each climbing fiber cause a burst of spikes in Purkinje cell
(called a “complex spike”) when new skilled movement is
done
 Complex spike causes long term modification of the pattern
of mossy fibre input to Purkinje’s cell.
 Climbing fibre input gets increased when new skilled
movement is learned
Normal spike Complex spike

24. Cerebellar dysfunction
Characteristics feature
 Disturbance of posture
 Hypotonia
 Face rotated towards opposite side
 Body weight thrown on healthy leg, concavity of trunk towards
affected side
 Nystagmus
 Ataxia
 Incoordination of movements
 Decomposition of movements (movement occurring in stages)
 Dysmetria- movement is poorly carried out in direction, range,
and force ;past pointing (hypermetria) or falling short
(hypometria) occurs

25. Cerebellar dysfunction
 Intention tremors:
 Jerky movements with to and fro motion on reaching an
object
 Coarse tremor occurring at 4-6/sec.
 Slow and lalling speech.
 Drunken gait
 Pendular reflexes
 Nystagmus

27. Physiotherapy management
Head and trunk control
Sitting balance
Supine to prone
Sitting to standing
Standing balance/ambulation
Ataxia rehabilitation
 Increase proprioception
 Increase balance
 Vestibular exercises