cerebellum by dr.sidra
TRANSCRIPT
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Learning Objective
• Describe the functions of Cerebellum
• Clinical abnormalities
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• Originate from inferior olive
• 1 fibre/5-10 purkinje cells
• Single impulse -Complex spike
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• Enter from multiple sources
• Synapse with 100 to 1000 granule cells
– Weak synaptic
connections – More fibers
– Activation – Simple
Spikes
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Glomerulus
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Neurons and Circuits of the Cerebellum
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Purkinje cells:
• Purkinje cells:
– 50 to 100 AP per second
• Deep nuclear cells at much higher rates
• Direct stimulation of deep nuclear cells –Excites them
• Signals from Purkinje inhibits them
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Vestibulocerebellum • Importance in maintaining balance
• Performance of rapid movements
– Change in direction
– Balance b/w agonist and antagonist muscles
• Problem is of time
– Most rapid conduction = 120 m/s --- 10 -15 millisec
– 10 inches movement occurred…………
– IMPOSSIBLE –RETURNING SIGNALS REACH AT TIME OF MOVEMENT
– Signals from periphery –
• Tell brain the rate and direction of movement
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• Vestibulocerebellum Calculate In
Advance
• INFORMATION FROM PERIPHERY AND VESTIBULAR
APPARATUS
• For anticipatory correction of postural motor signals– Necessary for maintaining equilibrium
• Peripheral body parts feedback through Vermis– Vestibulocerebellum help brain stem
• Vestibular nuclei• Reticular nuclei
– Compute required position of respective parts of body
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VESTIBULOCEREBELLUM
• MUSCLE TONE
• EQUILIBRIUM
• BALANCE
• EYE MOVEMENTS
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Spinocerebellum
• Provide smooth coordinate movements of agonist and antagonist muscles for– Acute purposeful patterned movements
• Cerebellum comparesIntentions of cerebral cortex
WithPerformance of respective parts of body
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Main connections of spinocerebellum
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SPINOCEREBELLUM
• TONE
• SYNERGY OF MOVEMENT
• POSTURE
• LOCOMOTION
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ROLE OF OLIVARY
AND PURKINJE SYSTEM
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Prevent overshoot and Damp movements
• Because of momentum
– All body movements are pendular
– All movements have tendency to overshoot
• Appropriate learned subconscious signals from
intact cerebellum stop movement precisely at
intended point
1. Provide damping
2. Prevent tremors and overshoot
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Cerebellar control of Ballistic movements
• Typing movements Ballistic movements• Scanning with eyes Saccadic movements
• If cerebellum removed:
– Movements slow to develop
– Force development is weak
– Movements are slow to turn off
Because there is
– No first excitatory and then delayed inhibitory signal by
cerebellum……
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Cerebro cerebellum• Lateral zone highly developed and enlarged
• Movements of hand & fingers and speech
performed
• No
– Direct information from periphery of body
– Direct contact with primary motor cortex
• But with premotor and association
areas
• If destroyed
– In-coordinate hand/finger movements?
– Speech is in-coordinate?
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Cerebro cerebellum
1. Planning of sequential movements
2. Timing of sequential movements
3. Extra motor predictive function
4. MOTOR LEARNING & COGNITIVE
ROLE
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Planning of sequential movements
• Planning of sequential movement - Dentate
Nuclei
• Start in sensory and premotor areas of cortex
• Transmitted to lateral zones of cerebellum
• Appropriate motor signals provide
transition from one movement to other
• Involved in PLAN of future movement
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Timing of sequential movements
• Provide appropriate timing for each movement
• Person recognize the need
• Predict ahead of time, how far different parts of
body will move in given time
• Smooth progression of movement
• If damaged : • Writing, Running, Speech uncoordinated
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Extra motor predictive function
• Rates of progression of visual and auditory
phenomenon
– Predicted by brain
–Need Cerebellum
• If large lateral portions of cerebellum of
monkey removed?
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Clinical abnormalities
– Dysmetria– Overshoot– Ataxia– Past pointing– Dysdiadochokinesia– Dysarthria(scanning speech)– Decomposition of movements– IntentionTremor
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– Cerebellar Nystagmus– Hypotonia– Rebound phenomena– Asynergia– Asthenia– Astasia– Postural changes and disturbance of gait– Disturbance in reflexes
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