9 - Cerebellum: Structure, Circuitry, and Function Flashcards
Where is the cerebellum located?
In the posterior cranial fossa.
What are the subdivisions of the cerebellum?
Flocculonodular lobe
Vermis
Anterior lobe
Posterior lobe
Name the blackend structures on the mid-saggital section (arbor vitae) of the cerebellum.
What 3 pairs of arteries supply the cerebellum?
Superior cerebellar artery: from the basilar artery.
AICA: from the basilar artery.
PICA: from the vertebral artery
What is the location of the anterior and posterior lobe of the cerebellum?
Anterior lobe: in front of the primary fissure
Posterior lobe: behind the primary fissure
Where are the cerebellar tonsils located?
Medial inferior part of the cerebellum.
They can herniate.
Describe the structure of the flocculonodular lobe? What is the function of it?
One nodule with 2 flocculi, separated from the posterior lobe by the posterolateral fissure.
Vestibulocerebellum: control of equilibrium, balance, and eye movements (VOR).
If spared in, comatosa pts may have “doll eyes” because their vestibulocerebellum is intact.
What are the three longitudinal subdivisions of the cerebellum?
Vermis: along the midline
Intermediate zone of cerebellar hemisphere
Lateral zone of cerebeller hemisphere.
What are the functions of the vermis, intermediate zone, and lateral zone of the cerebellum?
Vermis: spinocerebellum; control of axial and proximal limb movements
Intermediate zone: part of spinocerebellum; controls distal limb movements
Lateral zone: part of cerebrocerebellum; planning and initiation of movements (largely under cerebral control).
What are the two excitatory afferents of the cerebellar cortex?
Climbing fibers: from contralateral inferior olivary nucleus; synapse directly with purkinje cells
Mossy fibers: from all other sources; synapse with granule cells, which activate purkinje cells
What are the five major neuronal types in the cerebellar cortex? Which are inhibitory and which are excitatory?
Purkinje cells: inihibitory = output neurons of the cerebellar cortex
Granule cells: excitatory
Golgi cells: inhibitory interneurons
Basket cells: inhibitory interneurons
Stellate cells: inhibitory interneurons
What are the three layers of the cerebellar cortex?
Molecular layer
Purkinje cell layer
Granular layer
Which cells are in the molecular layer of the cerebellar cortex?
Parallel fibers of granule cells.
Climbing fibers from inferior olivary nucleus (ION)
Stellate cells
Basket cells
Which cells are in the Purkinje cell layer of the cerebellar cortex?
Purkinje cells.
Which cells are in the granular layer of the cerebellar cortex?
Granule cells
Golgi cells
Mossy fibers
What is the function of the deep cerebellar nuclei (DCN)? What does it recieve input from? What type of output does it give?
Major output neurons of the cerebellum.
Recieves collaterals of climbing and mossy fibers to the cerebellar cortex. Also recieves inhibitory input from purkinje cells of the cerebellar cortex.
Output from them is excitatory.
What is the dentate nuclei? Where is it located?
Largest and most lateral nuclei.
Recieves projections from the lateral zone of the cerebellar hemispheres.
What is the interposed nucleiu? What does it recieve projections from?
Emboliform + Globose
Recieves projections from the intermediate zone of the cerebellar hemispheres.
What is the fastigial nuclei? Where is it located and what does it recieve information from?
The most medial nuclei.
Recieves projections from the vermis and some input from the flocculonodular lobe.
What is the synaptic circuit that climbing fibers are involved in?
Climbing fibers > excitatory to purkinje fibers > inhibitory to deep cerebellar nuclei > excitatory output to other brain regions
What is the synaptic circuit that mossy fibers are involved in?
Mossy fibers > excitatory to granule cells, which form parallel fibers > excitatory to purkinje cells > inhibitory to deep cerebellar nuclei > excitatory output to other brain regions
What role do inhibitory interneurons have in the synaptic circuits of the cerebellum? What inhibits purkinje cells? What inhibits granule cells?
Basket and stellate cells in the molecular layer inhibit purkinje cells.
Golgi cells in the granular layer inhibit granule cells.
This circuit, in addition to the climbing and mossy fibers are the reason we can do motor learning.
What is the vestibulocerebellum? What is its function?
The flocculonodular Lobe and the Inferior Vermis
Controls balace and equilibrium while standing or moving, controls eye movements, coordinates movements of the head and eyes.
What provides input to the vestibulocerebellum (flocculonodular lobe)?
The vestibular labyrinth made of ipsi semicircular canals and maculae of the urticle and saccule, and the vestibular nuclei (justarestiform body) through the inferior peduncle.
From the visual centers, the lateral geniculate nucleus, superior colliculi, and visual cortex relay info via the pontine nuclei to the vestibulocerebellum.
What are the components of the spinocerebellum? What are its functions?
Vermis + intermediate Zone
Vermis controls axial and proximal limb of muscles
Int. zone: controls distal limbs
Both control ongoing execulation of movements
What is the first major afferents to the spinocerebellar tract (made of the vermis and intermediate zone)?
- The ipsilateral spinal cord and lower medulla: give rise to the:
- dorsal spinocerebellar tract for info on touch, stretch, and pressure and synapse on the dorsal nucleus of clark (C8-L3)
- Cuneocerebellar tract gets input from levels above C8 and synapses in the external cuneate nucleus - Contralateral inferior olivary nucleus: travels via the olivocerebellar tract
All of these go to the inferior cerebellar peduncle (restiform body).
What is the second major afferent to the spinocerebellar tract? How does it travel?
Info from the IPSI spinal cord crosses the midline and travels via the ventral spinocerebellar tract to the superior cerebellar peduncle on the contralateral side (brachium conjunctivum).
Then it crosses BACK to the other side and goes to the ipsilateral spinocerebellum (anterior lobe).
*This is a double crossing tract that ends on the same side it started.
What does the vestibular nuclei give rise to?
The vestibulospinal tract to control axial musculature and the medial longitudinal fasciculus to control head and eye movements.
What is the first major efferent of the spinocerebellum that comes from the vermis?
Vermis gets info from ehad anc neck and sends info through the fastigial nucleus (DCN).
DCN sends info through the superior cerebellar peduncle to the thalamus which sends info to the motor and premotor cortex.
DCN also sends info through the juxtarestiform body to the brainstem,w hichdoes the the medial descending systems (vestibulo, tecto, reticulo- spinal tracts) to axial and proximal muscles
What is the function of the efferents of the spinocerebellum that originate from the vermis?
Axial and proximal muscle control.
Control outgoing execution of movement.
What major efferent of the spinocerebellum comes from the intermediate zone?
Input to intermediate zone (mainly from limbs) goes to the interposed nuclei (DCN) called the emboliform and clobose.
DCN sends to:
- Thalamus > motor and premotor cortex > corticospinal tract > distal muscles
- Brainstem (red nucleus) > lateral descending systems (rubrospinal) > distal muscles
What is the function of the efferents in the spinocerebellum that originate in the intermediate zone?
Play a role in distal motor control and control ongoing execution of movement.
What is the function of the cerebrocerebellum (lateral zone)?
Initiation, planning, and mental rehearsal of complex motor actions.
What is the major afferent of the cerebrocerebellum?
The cortico-ponto-cerebellar tract.
From CONTRA cortex via the corticopontine tract to the pontine nuclei.
From pontine nucleua through the middle cerebellar peduncle (WHERE IT DECUSSATES) to the cerebrocerebellum.
What is the major efferent of the cerebrocerebellum (lateral zone)?
Cerebrocerebellum > dentate nucleus (DCN)> DECUSSATES to the CONTRA red nucleus> thalamus>motor and premotor cortex then
- Corticopontine > pons
- Corticospinal > DECUSSATES to spinal cord (ending ipsilaterally to where it started)
The cerebellum receives info about plans for movement from the motor and premotor cortex via the _____________ tract?
Corticocerebellar tract
The cerebellum monitors the integration of descending and peripheral information regarding movement in the spinal cord via the ____________ tract?
Ventral spinocerebellar tract
The cerebellum recieves feedback information from the sensory periphery via the __________ tract and __________ tract during the course of movement.
Dorsal spinocerebellar and cuneocerebellar tracts
The cerebellum projects to motor centers that send fibers to the spinal cord to adjust the output of the motor system. This is called the ___________ tract.
Dentatorubrothalamic tract.
The function of the cerebellum is changed by _______.
Experience.
This is called motor learning.
What do lesions of the cerebellum cause? Where are the motor signs typically?
Disruption of coordinated limb and eye movements, impaired balance, and reduced muscle tone. Can also impair motor learning.
Typically motor signs are IPSI.
What are major signs of injury to the cerebellum?
Ataxia - loss of full control of body movements
Hypotonia
Intentional tremor - seen in deliberate movements
Dysdiadochokinesia - cannot do pattern of alternating movements
Dysmetria - undershoot or overshoot of movements
Nystagmus
Titubation - nodding movements of the head or body
