export_cerebellum Flashcards
What are the functions of the cerebellum
It controls muscle tone, co-ordination, and equilibrium
What are the major components of the cerebellum
- Cortex
- Medullary substance
- Intrinsic nuclei
- Hemispheres
- Vermis
Convolutions in the cerebellum are called
Folia
What are the three lobes of the cerebellum
- Anterior
- Posteior
- Flocculonodular
What are the nine lobules of the vermis
- Lingula
- Centralis
- Culmen
- Declive
- Folium
- Tuber
- Pyramis
- Uvula
- Nodulus
From a phylogenic perspective how can the cortex of the cerebellum be classified
- Archicerebellum
- Paleocerebellum
- Neocerebellum
What are the components of the archicerebellum
Flocculus and nodulus.
Involved with vestibular function
What are the components of the paleocerebellum
Anterior lobe rostral to the primary fissure - lingula, centralis and culmen.
Control muscle tone with inputs from the stretch receptors.
What are the components of the neocerebellum
Posterior lobe between the primary fissure and the lateral fissures: declive, folium, tuber, pyramis, and uvula.
Controls co-ordination with inputs from the contralateral cortex via pontine relay nuclei.
What are the three cerebellar cortical layers?
- Molecular layer (most superficial)
- Purkinje cell layer
- Granular cell layer (most deep)
Features of the molecular cell layer of the cerebellum
Most superficial layer of the cerebellum. It contains basket and outer stellate cells. Axons from each basket cell touch 10 Purkinje cells.
Features of the Purkinje cell layer
Contains Purkinje cells. The myelinated axons here synapse with the deep nuclei and the lateral vestibular nucleus and send collateral fibers to excite Golgi type 2 cells.
Features of the granular cell layer
Contains granule cells and Golgi type 2 cells.
Features of the granule cells
Granule cells supply 4-5 dendrites to form a glomerulus and sends unmyelinated fibers to the molecular layer which bifurcate into parallel fibers and contact the Purkinje cell dendrites.
Features of the Golgi type 2 cells
Axons of the Golgi type 2 cells synpase in the glomeruli of the granular layer and send dendrites to the molecular layer which they synapse with parallel fibers.
Inputs to the cerebellum arrive via the
Superior, middle and inferior peduncles
The fiber tracts which provide cerebellar input are:
- Spinocerebellar
- Cunocerebellar
- Olivocerebellar
- Vestibulocerebellar
- Pontocerebellar
These fibers will all lose myelin in the cortex and end as mossy/climbing fibers.
With the exception of granule cells, climbing fibers and mossy fibers all cerebellar cells are inhibitory.
What are the 8 spinocerebellar tracts
- Dorsal spinocerebellar
- Ventral spinocerebellar
- Cuneocerebellar
- Rostral spinocerebellar
- Trigeminocerebellar
- Vestibulocerebellar
- Tectocerebellar
- Reticulocerebella
Features of the dorsal spinocerebellar tract
Uncrossed fibers.
Convey proprioception from joints and muscle spindles of ipsilateral lower extremities and upper trunk to Clarke’s nucleus in lamina 7 of the intermediate zone of the spinal cord.
These fibers then enter the inferior cerebellar peduncle to the cerebellar vermis and intermediate zone of the cerebellum as well as the fastigial and the interposed nuclei.
Features of the ventral spinocerebellar tract.
Crossed fibers.
Conveys efferent copies of motor commands, and exteroceptive and proprioceptive information to the lower extremities.
Cell bodies are spinal border cells in the anterior and intermediate horns, the tract ascends b/l crosses within the spinal cord and enters the superior cerebellar peduncle where it partly crosses again but remains mostly contralateral.
Features of the cuneocerebellar tract
Conveys proprioception of the upper extremities in the fasciculus cuneatus but synapses in the accessory cuneate nucleus in the caudal medulla and enters the inferior cerebellar peduncle ipsilaterally.
Upper extremity equivalent to the dorsal spinocerebellar tract
Features of the rostral spinocerebellar tract
Upper extremity equivalent to the ventral spinocerebellar tract.
Provides internal feedback, ispilateral and enters the inferior cerebellar peduncle
Features of the trigeminocerebellar tract
Conveys information from the mesencephalic, chief sensory and spinal nucleus of 5.
Mesencephalic –> middle cerebellar peduncle –> dentate and emboliform
Chief sensory –> quadrangular lobe and tonsil
Spinal nucleus (crossed and uncrossed fibers)–> tonsil
Features of the vestibulocerebellar tract
Monitors head position, eye movement and equilibrium.
Conveys fibers from CN 8 –> inferior cerebellar peduncle –>ipsilateral flocculonodular
Conveys inferior and medial vestibular nuclei –> juxtarestiform body –> bilateral flocculonodular lobe and fastigial nuclei
Features of the tectocerebellar tract
Conveys auditory and visual reflex information from the tectum –> anterior medullary velum –> superior cerebellar peduncle –> anterior and posterior lobes.
Features of the reticulocerebellar tract
Conveys information from the medulla –> inferior cerebellar peduncle –> vermis
Pons/reticulotegmental nucleus –> middle cerebellar peduncle –> vermis.
What two types of fibers provide afferent output to the cortex
- Mossy fibers
2. Climbing fibers
Features of mossy fiber input to the cortex
Mossy fibers from the spino/ponto/vestibulocerebellar tracts go to the granular layer to form the center of a glomerulus with a mossy fiber rosette. The mossy fiber stimulates granule cells vs Golgi type cells which inhibit them.
Each glomerulus contains: 1 mossy fiber; 20 dendrites of granule cells; Golgi type 2 cell’s axons and dendrites.
Features of climbing fiber input to the cortex
Climbing fibers from the contralateral inferior olivary complex to the molecular layer where they synapse on Purkinje cell dendrites, granule cell parallel fibers and basket and stellate cells.
What are the three corticonuclear projections seen from the cerebellum and what are their features?
- Vermis - fastigial nucleus
- Paravermian zone - interposed nucleus
- Hemisphere - dentate nucleus
These projections are bidirectional and unilateral.
The deep nuclei project to which layer of cerebellar cortex and release what kind of neurotransmitters?
Deep nuclei project to the granular cell layer.
They release excitatory neurotransmitters - aspartate and glutamate.
What are the four paired deep cerebellar nuclei
- Fastigial nucleus -> midline roof of the 4th ventricle, sends fibers to the vestibular system bilaterally
- Globose nucleus -> involved with tone
- Emboliform nucleus -> involved with tone
- Dentate nucleus -> largest, involved with coordination.
The globose and the emboliform nucleus together make up the nucleus interpositus
What kind of inputs to the deep nuclei can overcome the tonic inhibition from the cortex
Extracerebellar inputs.
Extracerebellar inputs to the deep nuclei
- Red nucleus -> nucleus interpositus (C)
- Principal olivary nucleus -> dentate (C)
- Medial and dorsal accessory olivary nuclei -> interposed nuclei (C)
- Medial accessory olive -> fastigial nucleus (C)
- Trigeminal sensory nucleus
- Reticulotegmental
- Locus ceruleus
- Raphe nucleus via climbing and mossy fibers.
Features of the afferent fibers in the inferior cerebellar peduncle
Restiform body -> contains only afferent fibers from the inferior olivary complex, pons and dorsal spinocerebellar tract
Juxtarestiform body(medial to the restiform body) -> contains afferent and efferent fibers from the vestibular system -> uvula, nodulus and fastigial nucleus
Features of the afferent fibers of the middle cerebellar peduncle.
The middle cerebellar peduncle only contains afferent fibers.
Cerebral cortex –> ipsilateral pons –> contralateral cerebellar hemisphere and bilateral vermis.
Features of the afferent fibers in the superior cerebellar peduncle
Afferent fibers in the superior cerebellar peduncle come from the ventral spinocerebellar tract.
The only part of the cerebellum without pontine input is the…..
Nodulus
Which cerebellar peduncles transmit efferent fibers?
Superior and inferior cerebellar peduncles
Features of the efferent fibers of the inferior cerebellar peduncle
Lie within the juxtarestiform body.
Fastigial nucleus to the pons, spinal cord, and bilaterally to the lateral and inferior vestibular nuclei.
Vermian cortex and flocculonodular lobe to the ipsilateral vestibular nucleus.
Flocculus –> superior and medial vestibular nuclei
Nodulus/uvula -> superior, medial and inferior vestibular nuclei
Fastigial nuclei -> vestibular nuclei
Features of the efferent fibers in the superior cerebellar peduncle
Dentate -> contralateral thalamic VL, VPLo and centrolateral nucleus -> cortex (ipsilateral coordination)
Dentate -> principal olive (Crossed fibers)
Emboliform nucleus -> dorsal accessory olive
Globose nucleus -> medial accessory olive
Nucleus interpositus -> contralateral red nucleus -> ipsilateral spinal cord (ipsilateral tone)
How is touch organized in the cerebellum
Ipsilateral in the anterior lobe and bilateral in the posterior lobe
How is audiovisual information organized in the cerebellum
Lies midline in the cerebellum
In the vermian zone Purkinje fibers inhibit the vestibular nuclei in order to
Decrease extensor muscle tone
The fastigial nucleus controls what?
Posture, tone equilibrium and locomotion.
The fastigial nucleus receives ipsilateral inhibition from the vermis but sends bilateral stimulation to the vestibular nuclei, pons, medulla, thalamus and cervical motor neurons.
The paramedian zone of the cerebellum controls what?
Controls ipsilateral flexor tone
Sends fibers to the nucleus interpositus which in turn travel to the thalamus and red nucleus.
The efferent fibers from the cerebellar hemispheres travel to..
- Dentate nucleus –> thalamic VL
2. VPLo –> motor cortex 4 for ipsilateral coordination.
Cerebellar lesions generally have ………… effects
Ipsilateral
Neocerebellar or posterior cerebellar lobe lesions produce what symptoms.
Hypotonia, fatigability, sluggish DTRs, decreased coordination, dysmetria, dysdiadokinesis, intention tremor, slow dysarthric speech, ipsilateral nystagmus
Paleocerebellar or anterior cerebellar lobe lesions produce
Transient increased extensor tone.
Archicerebellar or posterior vermian and floccular cerebellar lesions produce what symptoms
Truncal ataxia and equilibrium disorders.
