Cerebellum 33 Flashcards
Relative mass of the cerebellum in the brain?
10%
- Latin for Little Brain
Primary function of the cerebellum?
For motor learning
integrating sensory information
cognition
and modulating motor output
Percentage of neurons of the brain that are found in the cerebellum?
More than 50%
- over 50 billion neurons
- some of the largest neurons found here
Description of the cerebellum’s structure?
Highly folded
- stretched out flat would be ~1m long
What areas is the cerebellum divided into? (3)
Vestibulocerebellum (found under)
Spinocerebellum (found middle)
Cerebrocerebellum (found at the sides)
*given image shown in notes
Associated nuclei of the cerebellum (3)
Fastigial nuclei
Dentate nuclei
Interposed nuclei
Input and output of cerebellum through?
Cerebellar peduncles (inferior, middle, superior)
Output from the cerebellum through the cerebellar peduncles is by what type of cells? What affect do they have?
Purkinje cells: inhibitory
- reduces descending output
Vestibulocerebellum functions? (3)
VOR- ability to maintain focus with our eyes via vestibular system
Balance
Posture
- will be affected when improperly functioning
Vestibulocerebellum subdivisions? (2)
Flocculus and modulus
Vestibulocerebellum input and output?
Vestibular input from vestibular nuclei and directly from 8th cranial nerve
Output back to vestibular nuclei (within the brainstem)
Spinocerebellum function ? (2)
Sensory integration (efferent copy) and gain of descending output for multi-joint movements and dynamic stability
Spinocerebellum subdivisions (and relative location)? (2) - organization?
Intermediate zone and vermis
- vermis in middle and intermediate zone on on either side
- organized somatotopically: vermis controls axial (core muscles) balance
Spinocerebellum input and output?
Input: somatosensory info from periphery, visual and vestibular information
Output: vestibular nuclei, M1 areas via thalamus, other nuclei within brainstem (activation of CPGs) central pattern generators
Spinocerebellum nuclei? (2)
Interposed nuclei (intermediate) And Fastigial nuclei (vermis)
Spinocerebellum deficits? (Legions in this region)
Smooth control of muscles Gain of muscle tone Uncertain starts and stops Lateral deviations Unequal steps 74-93 of patients have fallen at least once per year (Can't walk straight)
Cerebrocerebellum functions? (3)
Visually guided and goal directed movements
Supraspinal control circuits
Planning of movements
Vestibulocerebellum deficits? (Caused by lesions). (3)
Balance
Posture
Eye movements
Cerebrocerebellum subdivions?
None
Cerebrocerebellum input and output?
Input: M1 Premotor cortex, frontal and parietal lobes
Output: thalamus - circuit of motor areas
Cerebrocerebellum nuclei?
Dentate nucleus
Cerebrocerebellum deficits? (4)
- visually guided movements (reach and grasp)
- dysdiadochokinesia (DDK impaired ability to perform rapid, alternating movements)
- dysmetria (lack of coordination, under or overshoot intended arm leg hand etc position - multijoint movements)
- rebound phenomenon (push down on someone’s arms as they hold it flexed, release will cause their arms to quickly contract back)
- locomotion generally intact
Common signs of cerebellar deficits?
Wide base of support
Ataxic gait (imbalance medial-lateral, purpose of wide base)
Impaired multi joint coordination
Dysdiadochokinesia - alternating movements
Dysmetria -over under shoot movements
Rebound phenomenon
Overshooting reactions to perturbations (difficulty regaining balance)
How is cerebellum involved in voluntary movements?
Feedback ( for slow movements)
- desired output “continuously compared” with actual output
- pro: actuate output / con: slow
Feedforward (for rapid movements)
- sensory feedback evaluated before output program is generated
- **adapts with experience
- coordinates muscle groups in trail and error fashion
Alcohols affect on the cerebellum?
Can cause LTD in cerebellum
Long term effects are “atrophy” (neuron cell death in cerebellum)
Results in ataxic gait (stumbling, uncoordination)
What happens when born without cerebellum? Why?
Some unable to adapt and live life in wheelchair
Others can live semi normal lives
- cerebellum is redundant, there are other systems that do same functions
Cerebellum vs basal ganglia, similarities?
Both revives massive ‘cortical input’
- only cerebellum receives real time sensory feedback (from thalamus and cortex)
Both send output to thalamus, which relays back to motor and Premotor cortex to influence cortical control of voluntary movement
Cerebellum vs basal ganglia, differences?
Basal ganglia: involved in planning and gain of complex movements
Cerebellum: concerned with coordinated execution of ongoing movements
- only cerebellum receives ‘real time sensory feedback’
Basal ganglia pathway
Cortex
Claudette and putamen (also receives modulatory inputs)
Relay nuclei (Globus Pallidus and Substantia nigra)
Thalamus
-back to cortex
Cerebellum pathway
Cortex
Cerebellum cortex (also receives modulatory inputs)
Relay nuclei (Fastigial and interposed Dentate)
Thalamus
-back to cortex
Cerebellum vs basal ganglia during complex task (signing your name)
- purpose of each structure?
Basal ganglia plays critical role in “preparatory phase”
- selection of a motor program
- motivation and context
Cerebellum governs coordination of ongoing movements
- sequencing, coordination of timing
- status info from sensory systems
