PHYSIOLOGICAL ACTION OF CEREBELLUM

1. CEREBELLUM
DEPARTMENT OF PHYSIOLOGY
SCHOOL OF MEDICAL SCIENCES AND RESEARCH
DATE:24-07-2018
NAME: SANJOG BAM
HUMAN BIOLOGIST

2. LEARNING OBJECTIVES
• Introduction
• Functional division
• Functional histology
• Input and output pathways to cerebellum
• Cerebellar connections
• Cerebellar disorders

3. Introduction
• Also called as little brain
• Located in posterior cranial fossa
• Lies over the fourth ventricle
• Has three surfaces:
 Superior surface
 Inferior surface
 Anterior surface
• Connected to brainstem by three
peduncles
• Extensively folded : folia
• Considered as coordinator ,
predictor and mediates skilled
manipulation of muscles

4.  Cerebrocerebellum: neocerebellum
• Consists of two main hemispheres
• Connections with cortex
• Corticopontocerebellum
• Planning and programming of the
movements.
Functional division of cerebellum
 Vestibulocerebellum: also called archicerebellum
• extensive and reciprocal connection with
vestibular nuclei
• Concerned with equilibrium and vestibulo-ocular
reflex.
 Spinocerebellum: paleocerebellum

5. Functional histology: outer cortex and inner containing deep cerebellar nuclei
1. Layer of cerebellar cortex
Consists three layer
o Molecular layer: interneurons that are basket cells and
stellate cells.
o Purkinje cell layers:
 Contains purkinje cells
 Largest neuron with extensive dendritic branches
 Also receive inputs directly from the climbing fibers
 Connecting links between cerebellar cortex and deep
cerebellar nuclei.
o Granular cell layer:
 Contains Granular cells and Golgi cells
 Golgi cells project to the granule cells and modify
granular cells output.
 Granular cells receive input from the mossy fibers
 Granular cells via parallel fiber projects to purkinje
cells and other interneurons.

6. Deep cerebellar nuclei
 Four paired deep cerebellar nuclei
 Serves as the relay and processing stations
 Dentate nucleus the largest deep nucleus
1. Nucleus Fastigius
 Lies deep vermal portion of the cerebellum
 Vermal cortical portion of spinocerebellum projects to
this nucleus
2. Nucleus Globosus and Nucleus Emboliformis
 Combinely known as nucleus interpositus
 Paravermal portion of spinocerebellum projects to this
nucleus
3. Nucleus Dentatus
 present in the hemispheric portion of the cerebellum
 Teeth like serrated morphology
Deep cerebellar nuclei project to the different parts brainstem and
thalamus as cerebellar output

7. Input pathway to cerebellum
• Afferent pathways from other parts of the brain
Corticopontocerebellar pathway
Olivocerebellar tract
Vestibulocerebellar fibers
Reticulocerebellar fibers
• Afferent pathways from the periphery
Dorsal spinocerebellar tracts
Ventral spinocerebellar tracts

8. Cerebellar connections
Cerebellar inputs
• Receives almost all sensory inputs including special sensory inputs
• Input to cerebellum reach via three route:
Mossy fiber input:
Major source of inputs
Carry direct proprioceptive inputs and input from cerebral cortex.
 projects mainly to the granular cells
Climbing fibers input
 convey inputs from inferior olivary nucleus to cerebellum
Proprioceptive input via olivocerebellar tract.
Fibers projects to Purkinje cells of cerebellum.

9. Other inputs:
 Receives monoaminergic inputs and inputs from thalamus along with other parts of brain.
 Fibers project to the deep cerebellar nuclei
CEREBELLAR OUTPUT
Cerebellum projects to all
descending pathways
Vestibulocerebellum directly
projects to vestibular nuclei without
relaying in deep cerebellar nuclei

10. Internal connections of cerebellum
Purkinje cell output to the deep cerebellar nuclei is inhibitory:
secretes GABA
Purkinje Cell Activity
Exhibits two types of action potential:
 Simple spikes: -generated in response to stimulation of mossy
fibers –parallel fiber input
 Complex spikes:- appears if climbing fibers is stimulated that
comes from olivary nucleus
-these complex spike APs are involved in motor learning
- Produce long term adjustment in motor responses.

11. Cerebellar disorder
Loss of the cerebellar nuclei
Loss of cerebellar facilitation of the motor cortex and brain stem motor nuclei
Hypotonia
Error in the rate, range, force and direction of movement
Ataxia
Due to cerebellar overshooting and failure of the cerebellar system to damp
the motor movement
Intentional tremor

12. Dysmetria
• The movement overshoots their intended mark and the brain overcompensate to opposite direction
• Lesions in the spinocerebellar tracts
Rebound phenomenon
• Inability to brake the movement promptly e.g movement of limb and movement exist in wide
arc.
• Important reason these patients show dysdiadochokinesia(failure of progression)
Failure of progression

13. THANK YOU