5.4 Cerebellum (Mastery Edition) Flashcards
Does the cerebellum project directly to the spinal cord?
- No
- It acts indirectly through brainstem/cortex (like basal ganglia)
- However: the spinal cord does project to the cerebellum, through the spinocerebellar pathway (which carry sensory information from peripheral proprioceptors)
Describe the role of the cerebellum in motor movement
- Planning and timing of motor activities (+ sensory motor coordination)
- Compares planned movement with actual movement, and adjusts accordingly
HOW does the cerebellum alter motor movements at the muscular level?
- Controls intensity of muscle contraction
- Controls antagonists and agonist muscle groups
Where does the cerebellum receive sensory information from? What plan does it compare it to? How does it exert its adjustments?
- Receives info from proprioceptors (e.g. muscle spindles)
- And from vestibulocerebellar pathway from vestibular apparatus
- Compares to efference motor copy from cortex
- Exerts effects from motor areas of cortex
The cerebellum is separated from the cerebral cortex by a dural fold known as the…
Tentorium cerebelli
The hemispheres of the cerebellum are separated by…
Falx cerebelli
What is the name given to the outer grey matter and inner white matter of the cerebellum?
Outer gray: folia (leaves)
Inner white: arbor vitae
Which section of the brain is the cerebellum located in?
The metencephalon
What are the names of the three CEREBELLAR peduncles?
- Superior
- Middle
- Inferior
Which areas of the brain do the three CEREBELLAR peduncles connect to?
- Superior: midbrain
- Middle: pons
- Inferior: medulla
Which of the three CEREBELLAR peduncles are afferent/efferent?
- Superior = efferent (to brain)
- Middle = afferent (from brain)
- Inferior = afferent
What are the three lobes of the cerebellum? What fissures separate them?
- Three lobes: anterior, posterior, and floculonodular
- Anterior and posterior are separated by the primary fissure. Posterior and FN are separated by the posterolateral fissure
Name the four pairs of cerebellar nuclei
- Dentate
- Emboliform
- Globose
- Fastigial
Alphabetised: D, E, F, G
What two pairs of cerebellar nuclei comprise the interposed nuclei?
Emboliform and globose
What are the three layers of cells in the cerebellar cortex? Broadly, what is each layer responsible for?
- Molecular layer Layer (Processing)
- Purkinje Cell Layer (Output)
- Granular Layer (Input)
Important: output is from cerebellar cortex; most ouput from the whole cerebellum comes from deep cerebellar nuclei.
Why are there relatively few cells in the molecular layer of the cerebellar cortex?
- Dendrites of the Purkinje cells are reaching up
- Axons of granular cells are also reaching up
- Less space for cells
What types of cells can be found in the molecular layer of the cerebellum? What ARE they?
- Stellate cells
- Basket cells
These are inhibitory interneurons (hence processing)
What kinds of cells can be found in the granular layer of the cerebellar cortex?
- Granule cells
- Golgi cells (inhibitory interneurons)
Which type of cell is the major input/output cells of the cerebellar cortex?
Input: granular
Output: purkinje
Describe mossy fibres, their course, and their interaction with others cells; what is the result of this?
- Mossy fibres travel up through cerebellar white matter and synapse with granular cells, exciting them
- Granular cells send axons up into the molecular layer, where they bifurcate, forming parallel fibres that run parallel to the folia of the cortex
- These fibres excite Purkinje cells than line the surface of of the molecular layer
- In turn, these Purkinje cells INHIBIT the vestibular and deep cerebellar nuclei
Which of climbing fibres and mossy fibres excite purkinje cells in a 1-to-1 vs 1-to-many fashion?
Mossy fibres: one to many
Climbing: one to one (more attention to clients; that’s why he’s climbing)
Describe the origin, course, and function of climbing fibres of the cerebellum
- Originate in contralateral inferior olivary nucleus
- Climb up through white matter directly to Purkinje cells
- Cause Purkinje cells to become LESS responsive to inputs from parallel fibres of granule cells
(He’s the 1-to-1 marketer who comes in and beats the 1-to-many webinar guy)
Describe how basket and stellate cells narrow the spatial extent of excitatory inputs to purkinje cells in the cerebellum
- Stellate and basket cells are excited by input from granule cell parallel fibres
- When excited, they laterally inhibit adjacent purkinje cells
- Stellate cells terminate on purkinje cell dendrites
- Basket cells terminate on purkinje cell bodies
How do golgi cells enhance the temporal resolution of cerebellar circuitry?
- Excited by input from parallel fibres from granule cells
- Provide feedback inhibition onto granule cell dendrites
Is the somatotopic organisation of the cerebellum ipsilateral or contralateral?
Ipsilateral. Unlike cerebral cortex.
Describe the somatotopic organisation of the cerebellum.
Guy standing on his head, then auditory/visual cortices, then guy standing upright (head/arms/legs)
Which fibres carry all the cerebellar input information (for our purposes, at least)?
- Mossy fibres (from different tracts, like spinocerebellar and pontocerebellar fibres)
- Climbing fibres (remember: these are from the contra inf. olivary nucleus)
Which cerebellar white matter nuclei get input from which parts of the cerebellum?
- Dentate: projections from lateral cerebellum
- Emboliform & Globose (Interposed nuclei): intermediate
- Fastigial: vermis/FN lobe
Efferent outputs leave the lateral and intermediate cerebellum via the superior CEREBELLAR peduncles; which thalamic nuclei do they go to, and where does the info head from there?
- Go to VL nucleus of CONTRALATERAL thalamus
- Go to premotor, primary motor, and supplementary motor areas, and to the old man in his observatory in the posterior parietal lobe for motor planning
Which section of the cerebellum is especially important in influencing lateral corticospinal output?
Intermediate; globose and emboliform (i.e. interposed) nuclei
What do the vermis and FN lobe of the cerebellum control? Which nuclei/thalamic nuclei/cortical areas are involved? Describe the pathway.
- Control extraocular movements and trunk muscles
- These cerebellar areas project to the fastigial nucleus
- Synapse on CONTALATERAL thalamic VL, and head to primary motor cortex
