Lecture 29: The Cerebellum Flashcards
The three functions of the cerebellum
- Maintenance of stable posture and coordination of reflex eye movements (through coordinating vestibular reflexes)
- Control of speed, distance, and force of movements in progress (“coordination”)
- Planning and timing of complex movements
**These a are accomplished by adjusting output of UMN pathway, they are middle management to LMN. cerebellum shapes UMN.
What the cerebellum does NOT do
NOT characterized by paresis or paralysis
NOT charcterized by a loss of sensory function
Gross cerebellar anatomy
- Folia and sulci (we don’t call the folds gyri like we do is the cerebrum)
- Vermis (means worm) - the armadillo!
- Cerebellar hemispheres (on other side of the vermis)
- cerebellar peduncles (on ventral lower side on either side of vermis)
- Rostral: Mostly output and connected to midbrain
- Middle: Mostly input and connected to pons
- Caudal: Mostly input (some output to vestibular nuclei) and connected to medulla oblongata
Layers in the folia:
Cerebellar cortex
Medullary ray (axons)
Outer layer: molecular layer
Deep to that: purkinje cell in Purkinje cell layer
Deeper still: granule cells, granule cell layer
what are the afferent (sensory) information of the cerebellum
- Unconcious proprioception
- Vestibular info
- Motor planning
** all of this information goes to the cerebellar cortex and the output comes from the pukinje cells and they are inhibitory to the deep cerebellar nuclei (which are tonically active) and then their target is the UMN so they have an output to influence UMN. the weird exception to this pathway is some purkinje cells project straight to vestibular nuclei, small minority.
The flocculonodular lobe
- Coordination of equilibrium and vestibular reflexes
- Input from vestibular apparatus and vestibular nuclei (inside brain stem)
- Output to UMN systems: vestibular nuclei (some via deep cerebellar nuclei, some via direct projections from purkinje cells)
- Influences vestibular motor tracts (MLF medial longitudinal fasciculus and LVST lateral vestibulospinal tract-two spinal cord pathways) for stable posture, coordination of eye movement
made up of the nodulus and floculus
the function of the Cerebellar (lateral) hemispheres (do not immediately itch up to the vermis)
Coordinates initiation, planning, and timing of complex movements
Input from motor cortices
Output to UMN systems: motor cortices
function of the vermis and paravermal zones
- Adjusting movements while in progress - coordination of voluntary movement (in progress)
- Coordination of ongoing movements: force, metering, and speed of voluntary movements
- Input = unconcscious proprioception
4 spinocerebellar tracts and trigeminocerebellar tract
name the nuceli for the cerebellar output to UMN systems:
Vestibular nuclei > LVST
REd nucleus > rubrospinal tract (dorsal medial)
Motor cortex> cortical motor tracts
Ventralmedial groove is vestibular spinal pathway and is for extension
What are the Spinocerebellar tracts (four of them, learn about two)
- The ventral spinal cerebellar tract (in the pelvic limb, A alpha type fibers, decusstes twice = ipsilateral)
- Rostral spinocerebellar tract (in the forelimb, A alpha fibers, ipsilateral:
- cuneocerebellar tract (forelimb)
- dorsal spinocerebellar tracts (hindlimb)
So think motor ataxia is cerebellum and sensory ataxia is DCML.
cerebellar disease vocab
- Dysmetria (esp hypermetria): abnormal metering
- Tremors (hallmark of cerebellar disease although other things can cause tremors, n.b.[nota bellae] Head tremors)
- Truncal sway
Increased muscle tone - Pendular [eye tremor] (or vestibular) nystagmus
- Loss of menace (not a reflex, is a reaction, has to be learned)
where is Cerebellar hypoplasia (small cerebellum) seen?
Feline panleukopenia (distemper)
BVD in cattle
Paradoxical vestibular disease
