Cerebellum I & II Flashcards
Cerebellum development
-develops as the dorsal part of metencephalon
-attached to pons
Ventral aspect of Cerebellum
-acts as a roof of the 4th ventricle
-lateral apertures allow for the flow of CSF into the subarachnoid space, which means CSF can be found external to the brain/spinal cord
Cerebellar lesion movement signs
-goofy, choppy movements
-can’t coordinate movements. Have inappropriate movements.
-head tremor
Common virus causing cerebellum lesion in cats
-panleukopenia
Cerebellar peduncles
*axon tracts in/out of the cerebellum
1.Rostral
2.Middle
3.Caudal
Information/pathways going to cerebellum
-proprioceptive information from spinocerebellar tracts of spinal cord into cerebellum
-brain stem nuclei leave brainstem and go to LMN in spinal cord BUT a copy of brainstem nuclei goes to cerebellum which allows for slight changes in movement (eg. Walking up hill vs. walking on flat ground)
-Cortical UMNs synapse on pontine nucleus and will supply copy to cerebellum so that it is aware of movements
Neurons from the cerebellum
-involved in modulating movements, sending signals to cortical UMNs and brainstem
>tells body “I know you want to eat from bowl, but bowl is farther away than originally thought”
Cerebral grey matter vs. cerebellar grey matter
-much tighter folds to increase SA/neuron capacity but it is confined to a small space
Vestibulocerebellum (flocculonodular node) input, output and function
-input for CN 8
-Output for vestibular nuclei in medulla
-function-vestibular system: maintain upright posture of head and body
Cerebrocerebellum (cerebellar hemispheres)
-input for cerebral cortex via pontine nucleus
-output for cerebral cortex via thalamus
-Function- higher order movements (planning, timing, learning/muscle memory)
Spinocerebellum (cerebellar vermis)
-input spinocerebellar tracts (caudal peduncle) and brainstem UMNs
-output for brainstem UMNs
-function- proper coordination of limb muscles and movements
Spinocerebellum input specific function
-proprioceptive tracts and copy of motor movement commands sent to spinal cord by brainstem nuclei
Spinocerebellum output specific function
-corrections to adjust motor movements to make sure they are appropriate
Goes to brainstem UMNs
Cerebellum neurons
- the cerebellum does not contain UMNs
> no paresis/paralysis caused by lesions
-the cerebellum does not initiate movements (only coordination and modifications to motor movements)
> lesions causes ataxia, but it will not ability to move
Three characteristics of motor movements
1.rate
2. range
3. force
**cerebellum is responsible for ensuring that these characteristics are appropriate for the circumstance AND will adjust in real-time to changes in environment
Lesions of cerebellum
1.ataxia= cerebellar ataxia (exaggerated/choppy gait)
2.proprioceptive deficits= hopping, knuckling are abnormal
>NOTE: these animals will never lose proprioception, but they will be exaggerated!
3.increased muscle tone, especially of extensor muscles (occurs because UMNs are not inhibited by cerebellum resulting in UMNs sending increased signal to LMN=increased tone)
4. Not paralyzed
>no paralysis, no paresis because UMN are intact
5.Tremors (will often worsen with movements- intention tremor)= dysmetria
>True tremor is a cerebellum sign most of the time. Animal trying to do movement but not sure how to do it because cerebellum damage
6.Loss of menace response
>menace pathway goes through cerebellum, so needed for control.
7. Truncal ataxia= broad based stance (with truncal sway)
>due to animals being aware that they are off balance
8.Vestibular disease signs
>head turn, falling to one side, rolling,
>ear infections
9. Opisthotonus- hyperextension of body/head/limbs
>severe lesions (can be cortical, brainstem or cerebellar lesions)
Menace response
-learned response involving CN II, animal will see something coming towards them, send signal to brain and cerebellum and then they will blink (CN VII). Young animals won’t have learnt behaviour yet.
Hypermetria
-hypermetric gait can be seen in both a cerebellar lesion and C1-C5 lesion
Cerebellar damage: slamming everything down, choppy excessive movements
Spinal C1-C5 segment damage: smooth, excessive movements
Ataxia movement due to cerebellar lesion
-dysmetria, specifically hypermetria
◦ too fast
◦ too forceful
◦ too far
-truncal sway
Bilateral cerebellar lesion
-widespread, diffuse disease
Focal lesion of cerebellum or brainstem
-will get ipsilateral signs
-sometimes bilateral signs
Contralateral signs
-think forebrain, not cerebellar
Causes of cerebellar lesions
-neoplasia
-infections (fungal, viral, bacteria)
-metabolic disorders/toxins
-abscesses
-increased ICP
-congenital malformations/hypoplasia/atropy
-caudal/ventral skull fractures
-herniation
-trauma (cerebral edema, hemorrhage)
-ischemia/stroke
-high altitude cerebral edema
