The cerebellum Flashcards
What is the function of the cerebellum?
Comparitor of sequence of muscle contractions, calibrations and coordination –> fine tuner of small fine movements
What types of disorders can you get with a cerebellum lesion?
- Ataxia: uncontrolled and inaccurate movements
- Dysynergia: disturbance of the synergy in multi-joint movements
- Dysmetria: overshoot and undershoot of target
Which cerebellar peduncles have we and what is their in or output?
- Superior: output to thalamus
- Middle: input to cerebellum
- Inferior: input and output
How can the cerebellum get damaged?
- Physical trauma
- Cutting of the bloodflow (superior cerebellar)
- Alcoholism (damaging purkinje cells in anterior lobe)
- Cancer (degenaration of purkinje cells)
- Unilateral lesion produces ipsilateral symptoms
What is the function of the spinocerebellum?
(middle part cerebellum)
Adjustments of ongoing movements and controlling muscle tone and multiple joint movements of body and limbs
The vermis is part of the spinocerebellum, what is its function?
Adjusting current movements and regulating muscle tone for balance and core muscles
What is dysdiadochokinesia?
Errors in timing of muscle contractions of rapid alternating movements
What does the cerebrocerebellum do?
(side of cerebellum)
Planning and initiation of fine movements + skilled movements of distal extremities in context of the motor plan.
What happens when there is a lesion on the right side of the cerebrocerebellum?
Fine tuning of the right hand will go wrong
What is dysmetria?
Errors in estimation of distance and direction of target
- Produces over/undershoot
What are intention tremors?
Repeated overshoot and undershoot usually at the end of the movement
What is the function of vestibulocerebellum?
(bottom of cerebellum)
Regulating balance and reflex eyemovements
- It receives input from the vestibular nuclei in the dorsolateral tegmentum in the medulla and pons
What are the 2 primary input fibers of the cerebellum? And where comes there input from
Mossy and climbing fibers, they are both excitatory
- Mossy has input from cortex, brainstem and spinal cord
- Climbing has input from inferior olive
Which input fiber from the cerebellum is connected to upper motor neurons and lower motor neurons?
Climbing fibers –>
- Connected to upper via exernal cuneate nucleus
- Connected to lower via dorsal nucleus of Clarke
With which nuclei are mossy fibers indirect connected with corticobulbar projections?
Pontine nuclei
What is the function of the inferior olive for the cerebellum?
Its the learning signal for the cerebellum. It will give an error correction signal that improves performance
‘Time to change’ signal
- Its involved in control and coordination of movements, sensory processing, cognitive tasks and encodes the timing of sensory input independently of attention/awareness
What happens with the purkinje cells when the inferior olive gives the time to change signal
Climbing fibers will take over control and excite purkinje cell
What happens when there is a lesion in the inferior olive?
There is a decreased ability to perfect highly specialized motor tasks such as improving one’s accuracy in hitting a target with a ball
What are the indirect output targets from the cerebellum to the cerebrum?
Motor cortex, reticular formation and brainstem (via deep cerebellar nuclei)
What are the direct output from the cerebellum to the spinal cord?
Vestibular nuclei via inferior cerebellar peduncle
What are the 3 layers of the cerebellar cortex?
Molecular, purkinje cell, granule cell
What are the 5 cell types in the cerebellar cortex?
Purkinje, granule, stellate, basket, golgi
Which cell types are the targets of climbing and mossy fibers?
- Purkinje cells are the excitatory target of climbing fibers output
- Granule cells are the excitatory target of mossy fibers
What happens to a deep cerebellar nuclear cell when a purkinje cell is being excited by a climbing fibre?
The purkinje cell inhibits the deep cerebellar nuclear cell.
NOTE
The mossy and climbing fibers can directly excite the deep cerebellar nuclear cell
What happens when parallel fibers and climbing fibers are simultaneously stimulated? And how?
Longterm inhibition of excitation:
- There is an increase of intracellular [Ca2+] –> increased PKC activation –> PKC phosphorylates substrate proteins –> internalization of AMPA receptors –> LTD
