physiology of cerebellum

1. CEREBELLUM
Dr.Dina Merzeban
lecturer of physiology
http://facebook.com/physiology.dina

2. • The cerebellum is vital to the control of
rapid movements.
• Damage to the cerebellum does not
usually produce muscle paralysis but
rather causes an inability to use the
affected muscles in a rapid, smooth, and
coordinated manner.

3. SCHEMATIC REPRESENTATION OF THE MAJOR
ANATOMICAL SUBDIVISIONS OF THE CEREBELLUM.

4. PHYLOGENETIC ORGANIZATION
Spinocerebellum
Pontocerebellum
Vestibulocerebellum

5. DEVELOPMENT OF CEREBELLUM
Archicerebellum (nodulus)
Archicerebellum (flocculus)
Paleocerebellum
Neocerebellum

6. FUNCTIONAL ORGANIZATION OF CEREBELLUM

7. FUNCTIONAL AND PHYLOGENETIC ROLE
Phylogenetic
denomination
Anatomical parts Role
Vestibulocerebellu
m (Archicerebellum)
Flocculonodular lobe
(+ adjacent vermis)
Regulates balance and eye
movements.
Spinocerebellum
(Paleocerebellum)
Vermis and
intermediate parts of
the hemispheres
("paravermis")
Regulates body & lim
b movements.
The spino cerebellum
receive
proprioceptive input
to compare the actual
performance of a
given movement with
the intended
movement of the
brain.
Cerebrocerebellum Middle portion of the involved in planning & initiation of
movement.It has purely cognitive
functions as well.
(Neocerebellum) vermis & Lateral
parts of the

8. CEREBELLAR NUCLEUS
Dentate n.
Emboliform n.
Globose n.
Fastigial n.

9. MOTOR MODULATION BY THE CEREBELLUM

10. INPUT OF CEREBELLUM

11. Output (Efferent) Signals From the Cerebellum
All outputs from the cerebellum originate from the
cerebellar deep nuclei. Thus, a lesion to the cerebellar nuclei
has the same effect as a complete lesion of the entire
cerebellum.
v The vermis of the cerebellar cortex project to the
fastigial cerebellar nucleus and then to the vestibular nuclei
and reticular formation.
v The intermediate zone projects to the globose and
emboliform nuclei (interposed nuclei) then they project to
the contralateral red nucleus (the origin of the rubrospinal
tract).
v The Lateral hemisphere projects to the dentate
(lateral) cerebellar nucleus and then to the ventro-lateral and
ventro-anterior thalamic nuclei, which project to the cerebral
cortex.

12. • The cerebellum results in deficits to the
ipsilateral side of the body.
The cerebellum have connections with the
contralateral cerebral cortex and the ipsilateral
spinal cord.

13. THE SPINOCEREBELLUM CONTAINS TWO SOMATOTOPIC
NEURAL MAPS OF THE BODY

14. NEURONAL CITCUITS OF CEREBELLUM

15. The Purkinje Cell and the Deep Nuclear Cell
The principal cell type is the Purkinje cell, which receives input
to its fan-shaped dendritic tree located in the molecular layer.
This input comes from two main sources:
1) climbing fibers that originate from cells of the inferior
olivary complex
2) parallel fibers that represent axons of granule cells.
 The granule cells receive synaptic input from mossy fibers,
which are formed by all the other cerebellar afferent systems.

17. • 1) The deep cerebellar nuclear cells exhibit a high
level of background activity, which can be increased
or decreased.
• 2) The central nuclei receive direct excitatory input
from climbing fibers and most mossy fiber systems,
whereas the input from Purkinje cells is inhibitory.
• 3) The inhibitory interneurons (basket cells, stellate
cells, Golgi cells) in the cerebellar cortex also
influence the transmission of signals through the
fundamental circuit.

18. Functions of the cerebellum
1.The Cerebellum Has a Turn-on/Turn-off Function.
• Because mossy and climbing fiber ----- excitatory------- the turn-on
signal.
• they can activate Purkinje cells that inhibit cerebellar nuclear
neurons and in this way specify the turn-off signal.
• Such theory may explain the inability to perform rapid alternating
movements; dysdiadochokinesia (e.g., pronation-supination of the
wrist)

19. Functions of the cerebellum
2.Purkinje Cells Correct Motor Errors.
• the climbing fiber input to a Purkinje cell modify its
sensitivity to parallel fiber input of the granule cells.
• During the time of increased climbing fiber activity, the
Purkinje cell can become more or less responsive to
parallel fiber input.
• The climbing fiber input is more vigorous when a
mismatch occurs between the predicted result of a
movement and its actual result.
• Gradually, as the movement is practiced, the mismatch
declines and climbing fiber activity begins to return to its
previous level.

20. NEURONAL CITCUITS OF CEREBELLUM

21. Functions of the cerebellum
3.The cerebellum regulates Equilibrium and
Posture.
• The vestibulocerebellum joins with the brain
stem and spinal cord to regulate equilibrium and
posture.
• calculate the rate and direction of movement;
i.e. where the body will be in the next few
milliseconds.
• it is associated mainly with axial and girdle
muscles, maintaining the posture appropriate
for a movement.

22. Floculonodular
Lobe
Vermis
Vestibular
Organ
lower motor neuron
LMN
FASTIGIAL
NUCLEUS
ARCHICEREBELLUM
VESTIBULAR NUCLEUS
vestibulospinal tract

23. 4.Servo-comparator function
• The spinocerebellum appears to function as a
comparator. A copy of the motor command via
the cotico-ponto-cerebellar tract.
• Once the motor act begins, the cerebellar cortex
begins to receive input (via spinocerebellar
tracts)
• spinocerebellum compare
• The deep nuclear cells of the cerebellum send
corrective actions both at the cortical level
through ascending pathways, as well as at the
spinal cord level through descending pathways.

24. Servo-comparator function

25. 5.Damping effect of the cerebellum
The spinocerebellum may be involved in
damping movements (braking effect). For
example, when an arm is moved,
momentum develops and must be
overcomed to stop the movement.
• When lesions affect the spinocerebellum,
overshoot -------- intention kinetic tremors.

26. 5.Damping effect of the cerebellum
Extremely rapid movements(typist)are called
ballistic movements, entire movement is
preplanned to go into motion, travel a specific
distance, and then come to a stop.
• These types of movements are disrupted when
the spinocerebellum is damaged. The movement
is slow to be initiated, its force development
is weak, and it is slow to be terminated, which
results in overshoot or past pointing.

27. 6.The planning, sequencing and timing of
movement
• The cerebro-ponto-cerebellar
• The plan of an intended, sequential movement
is transmitted from the premotor and sensory
cortex
• activity in the dentate nucleus reflects the
movement that will be performed, not the
ongoing movement.
• So the cerebrocerebellum plans for the next
movement at the same time the present
movement is occuring.

28. MAIN CONNECTIONS OF THE NEOCEREBELLUM
CEREBRAL
CORTEX THALAMUS
Pontine
Nucleus
Lower motor
neuron LMN
DENTATE
NUCLEUS
POSTERIOR
LOBE
CEREELLAR
HEMISPHERE
NEOCEREBELLUM
Pyramidal
tract

29. 7.Effect of the cerebellum on muscle
tone:
The neocerebelium is facilitatory while the
paleocerebellum is inhibitory.

30. Neocerebellar syndrome
Ataxia : is the incoordination of movement
due to errors rate range force of movements
in the absence of motor paralysis or sensory
deficit.
• Occur due to damage of deep cerebellar
nuclei or cerebellar cortex.
• The manifestations occur on the same
side of the lesion

31. Neocerebellar syndrome
Manifestations:
•Dysmetria: movements overshoot or undershoot
the intended target.
•Past pointing: is failure of a movement signal to
be terminated at the proper time, and the limb
continues past or beyond its intended target.
•Intention tremor: is a type of tremor present only
when a voluntary movement is attempted and that
intensifies as the limb approches its target.

32. Neocerebellar syndrome
•Decomposition of movement: This is reflected in
difficulty with both simple and compound
movements. Movement initiation and termination is
affected.
•Rebound phenomenon: is due to absent damping
or braking effect of the cerebellum.
•Dysdiadochokinesia: is the inability to perform
rapid, alternating movements. The switch that
shifts from flexion to extension (or vice versa) is
not timed properly.

33. Neocerebellar syndrome
Manifestations:
• Stacatto speech: is a speech defect that
involves inappropriate progression from one
syllable to the next.
slurred speech in which some syllables are held
and others are dropped too quickly.
•Cerebellar nystagmus: is a tremor of the eyes
when attempting to fixate on a point in the
periphery of the visual field.

34. •Hypotonia: is decreased muscle tone in the
affected muscles, accompanied by
diminished reflexes.
• Disturbed gait : wide based, drunken gait
with tendency to fall on the side of the
lesion.

35. THANKS