Cerebellum Flashcards
What is the role of the cerebellum?
Involved in equilibrium, muscle tone, postural control, and coordination of voluntary movement
Where does input to the cerebellum go and how does it get there?
Cerebellar cortex; via 3 cerebellar peduncles
Where does output to the cerebellum go and how does it get there?
Deep cerebellar nuclei; thalamic or brainstem structures
Describe the primary fissure of the cerebellum
Separates anterior and posterior lobes
Describe the posterolateral fissure of the cerebellum
Separates posterior and flocculonodular lobes
What are the 3 longitudinal zones of the cerebellum?
- Vermis (medial)
- Intermediate/paravermal zone - medial hemisphere
- Lateral hemisphere
Where does the floculonodular lobe receive input from?
- Vestibular system, vestibulocerebellum
Where do the vermis and the intermediate hemisphere receive input from?
-Spinal cord; spinocerebellum
Where do the lateral lobes receive input from?
- cerebral cortex relayed through the pontine nuclei; neocerebellum or cerebrocerebellum
- always some overlap for different systems - not completely contained in each lobe
What is the role of the corticopontocerebellar pathway?
- brings voluntary motor intention information to the cerebellum
What are the results of lesions to the inferior olivary nucleus?
- produce widespread defects similar to complete destruction of entire cotralateral half of cerebellum
Describe the somatotopic map in the anterior lobe of the cerebellum
Homunculus upside down with head near the primary fissure
Describe the 2 somatotopic maps of the lateral lobes of the cerebellum
Homunculus sitting upright with back to midline
What are the 3 layers of the cerebellar cortex? Describe them
Granular layer - deep layer of cell bodies close to white matter
Molecular layer - superficial layer of dendrites
Purkinje Cells - intermediate layer of cells between granular layer and molecular layer; these cells project from the cerebellar cortex to deep cerebellar nuclei (dendrites are in the molecular layer)
Describe the 3 fiber types in the molecular layer of the cortex
Parallel Fibers - belong to granular cells - synapse with purkinje cells
Climbing Fibers - belong to cells of contralateral inferior olivary nucleus
Mossy fibers - all other central connections, including pontine, brainstem/vestibular, and spinal cord input
Describe the dentate nucleus (lateral)
- Receives input from lateral cerebellum
- Projects to lateral cerebellum and VL/VA of thalamus
- Involved with planning movements
Describe the interposed (Emboliform/Globose Nuclei) (intermediate)
- input from intermediate cerebellum
- Projects to brainstem structures (red nucleus)
- adjusts limb movements
Describe the fastigial nucleus (medial)
- Input from vermis
- Projects to reticular formation and vestibular nuclei
- Responsible for postural adjustments and head movement
What are the cerebellar outputs?
- lateral cerebellum
- vermis
- Intermediate cerebellum
Describe cerebellar lesions and their principle signs
- typically get motor disorders without significant sensory deficits; Deficits affect the ipsilateral side
- Signs = ataxia, nystagmus
How would a lesion to the lateral cerebellum/dentate nucleus present?
- affects learned, skilled movements that become more precise and automatic with practice
- affect ipsilateral (cerebellar) side of body (C/L motor cortex)
How would a lesion to the intermediate cerebellum present?
-overshooting of targets or inability to readily grasp objects
What is the role of the intermediate cerebellum?
- Compares commands from the cerebral cortex (via pontocerebellar tract) with the actual body position and velocity of the moving parts (via spinocerebellar tract) and issues corrections
What is the role of the vermis?
- regulation of posture and stereotyped movements (ex. walking)
