CEREBELLUM Flashcards
GENERAL FEATURES
The cerebellum is located …
and the relation with fourth ventricle
located dorsal to the pons and the medulla
the fourth ventricle between the cerebellum and the dorsal aspect of the pons
GENERAL FEATURES
Cerebellum is derived from…
Metencephalon
GENERAL FEATURES
The cerebellum functions …
(2)
Planning
+
Finetuning
skeletal muscle contractions by comparing intended with actual performance
GENERAL FEATURES
The cerebellum anatomy
vermis
+
lateral cerebellar hemispheres
(2)
GENERAL FEATURES
The cerebellum cortex
multiple parallel folds
(folia)
+
several maps of the skeletal muscles
GENERAL FEATURES
The cerebellum functional division
Vermis
(axial and proximal musculatures)
Intermediate Hemisphere
(distal musculature)
Lateral Hemisphere
(motor planing)
GENERAL FEATURES
The cerebellum axial division
(lobes)
Anterior Lobe
Flocculonodullar Lobe
(balance and eye moviment)
Posterior Lobe
GENERAL FEATURES
Major input to the cerebellum
and
Major outflow from the cerebellum
INPUT
Inferior Cerebellar Peduncle
(restiform body)
+
Middle Cerebellar Peduncle
OUTFLOW
Superior Cerebellar Peduncle
GENERAL FEATURES
Principle Input of each cerebellar functional region
(3)
CEREBELLAR CYTOARCHITECTURE
Gray vs White matter
cortex (gray matther)
outer
+
medullary substance (white matter)
internal
CEREBELLAR CYTOARCHITECTURE
The 3 cell layers of the cortex are…
Molecular Layer
Purkinje Layer
Granule Cell Layer
CEREBELLAR CYTOARCHITECTURE
Molecular Layer
(4)
Outer layer
Basket and Stellate cells
Parallel fibers (axons from granule cells layer)
Dendritic tree of the Purkinje cells
CEREBELLAR CYTOARCHITECTURE
Purkinje Layer
Middle layer (most important)
All of the inputs to the cerebellum are direted to the Purkinje cells and only axons of Purkinje cells leave the cerebellar cortex
Single axon exits from each Purkinje cell
Punkinje cell projects to deep cerebelar nuclei or vestibular nuclei (brain stem)
CEREBELLAR CYTOARCHITECTURE
Granule Cell Layer
Innermost layer
Golgi cells + Granule cells (only excitatory neuron)
Glomerulus
(glial capsule + granule cell + axons of Golgi cells)
CEREBELLAR CYTOARCHITECTURE
Cell Types
CEREBELLAR CYTOARCHITECTURE
Internal white matter
(contains)
Deep cerebellar nuclei
Dentate Nucleus
Interposed Nuclei
(emboliform + globose)
Fastigial Nucleus
CEREBELLAR CYTOARCHITECTURE
Two kinds of excitatory input (afferent fibers)
Climbing Fibers
+
Mossy Fibers
obs: both types can influence the firing of deep cerebellar nuclei by axon collaterals
CEREBELLAR CYTOARCHITECTURE
Climbing Fibers
(3)
Originated from Inferior Olivary Complex
(contralateral side of the medulla)
Direct powerful monosynaptic excitatory input
CEREBELLAR CYTOARCHITECTURE
Mossy Fibers
Axons from all other sources of cerebellar input
(vestibular nuclei, spinal cord and others)
Indirect and diffuse excitatory input
Synapse with granule cells
Each granule cell send its axon into molecular layer
(parallel fibers)
CIRCUITRY
Tha basic cerebellar circuits
Purkinje Cell receive excitatory input from
climbing fibers (directly)
parallel fibers (granule cells)
→
Purkinje Cell project an inhibitory stimulus to deep cerebellar nuclei (or vestibular nuclei)
CIRCUITRY
Others circuitries
(inhibitory)
(2)
Golgi Cells
(receive an excitatory input from mossy fibers and from parallel fibers + inhibit the granule cell in glomerulus)
Basket + Stellate Cells
(receive an excitatory input from parallel fibers + inhibit Purkinje cells)
CIRCUITRY
Outflow (projections) from Purkinje Cells
(4)
Purkinje Cells
Flocculonodular Lobe → lateral vestibular nucleus
Vermis → fastigial nuclei
Intermediate Hemisphere → interposed nuclei
Lateral Hemisphere → dentate nucleus
CIRCUITRY
Major pathway
Purkinje cells → deep cerebellar nucleus (dentate and interposed) → superior cerebellar peduncle → contralateral ventrolateral (VL) nucleus of the thalamus → motor cortex (first degree) → pontine nuclei → contralateral cerebellar cortex
CIRCUITRY
Others efferents from the cerebellum
(3)
CLINICAL FEATURES
The hallmark of cerebellar dysfunction
Tremor with intended movement without paralysis or paresis
ipsilateral
(contralateral outflow to thalamus, then contralateral fibers in corticospinal tract)
CLINICAL FEATURES
Dysfunction in lesions
(hemisphere vs vermis)
Hemisphere
intention tremor, dysmetria, dysdiadochokinesia, dysarthria, nystagmus, gaze dysfunction and hypotonia (ipsilateral)
Vermis
truncal ataxia
CLINICAL FEATURES
Alcohol Abuse
Anterior Vermis
+
Gait ataxia
CLINICAL FEATURES
Medulloblastomas or Ependymomas
Posterior Vermis
+
Truncal ataxia
CLINICAL FEATURES
How to differentiate vermal lesions from dorsal columns lesions?
(both result in difficulty maintaining posture, gait or balance)
Romberg Sign
vermal lesion - romberg - (symptoms when eye opened)
dorsal column lesion - romberg + (symptoms when eye closed)
