5.4 Cerebellum (Mastery Edition)

Question 1

Does the cerebellum project directly to the spinal cord?

Answer 1

• 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)

Question 2

Describe the role of the cerebellum in motor movement

Answer 2

• Planning and timing of motor activities (+ sensory motor coordination)
• Compares planned movement with actual movement, and adjusts accordingly

Question 3

HOW does the cerebellum alter motor movements at the muscular level?

Answer 3

• Controls intensity of muscle contraction
• Controls antagonists and agonist muscle groups

Question 4

Where does the cerebellum receive sensory information from? What plan does it compare it to? How does it exert its adjustments?

Answer 4

• 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

Question 5

The cerebellum is separated from the cerebral cortex by a dural fold known as the…

Answer 5

Tentorium cerebelli

Question 6

The hemispheres of the cerebellum are separated by…

Answer 6

Falx cerebelli

Question 7

What is the name given to the outer grey matter and inner white matter of the cerebellum?

Answer 7

Outer gray: folia (leaves)
Inner white: arbor vitae

Question 8

Which section of the brain is the cerebellum located in?

Answer 8

The metencephalon

Question 9

What are the names of the three CEREBELLAR peduncles?

Answer 9

• Superior
• Middle
• Inferior

Question 10

Which areas of the brain do the three CEREBELLAR peduncles connect to?

Answer 10

• Superior: midbrain
• Middle: pons
• Inferior: medulla

Question 11

Which of the three CEREBELLAR peduncles are afferent/efferent?

Answer 11

• Superior = efferent (to brain)
• Middle = afferent (from brain)
• Inferior = afferent

Question 12

What are the three lobes of the cerebellum? What fissures separate them?

Answer 12

• Three lobes: anterior, posterior, and floculonodular
• Anterior and posterior are separated by the primary fissure. Posterior and FN are separated by the posterolateral fissure

Question 13

Name the four pairs of cerebellar nuclei

Answer 13

• Dentate
• Emboliform
• Globose
• Fastigial

Alphabetised: D, E, F, G

Question 14

What two pairs of cerebellar nuclei comprise the interposed nuclei?

Answer 14

Emboliform and globose

Question 15

What are the three layers of cells in the cerebellar cortex? Broadly, what is each layer responsible for?

Answer 15

• 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.

Question 16

Why are there relatively few cells in the molecular layer of the cerebellar cortex?

Answer 16

• Dendrites of the Purkinje cells are reaching up
• Axons of granular cells are also reaching up
• Less space for cells

Question 17

What types of cells can be found in the molecular layer of the cerebellum? What ARE they?

Answer 17

• Stellate cells
• Basket cells

These are inhibitory interneurons (hence processing)

Question 18

What kinds of cells can be found in the granular layer of the cerebellar cortex?

Answer 18

• Granule cells
• Golgi cells (inhibitory interneurons)

Question 19

Which type of cell is the major input/output cells of the cerebellar cortex?

Answer 19

Input: granular
Output: purkinje

Question 20

Describe mossy fibres, their course, and their interaction with others cells; what is the result of this?

Answer 20

• 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

Question 21

Which of climbing fibres and mossy fibres excite purkinje cells in a 1-to-1 vs 1-to-many fashion?

Answer 21

Mossy fibres: one to many
Climbing: one to one (more attention to clients; that’s why he’s climbing)

Question 22

Describe the origin, course, and function of climbing fibres of the cerebellum

Answer 22

• 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)

Question 23

Describe how basket and stellate cells narrow the spatial extent of excitatory inputs to purkinje cells in the cerebellum

Answer 23

• 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

Question 24

How do golgi cells enhance the temporal resolution of cerebellar circuitry?

Answer 24

• Excited by input from parallel fibres from granule cells
• Provide feedback inhibition onto granule cell dendrites

Question 25

Is the somatotopic organisation of the cerebellum ipsilateral or contralateral?

Answer 25

Ipsilateral. Unlike cerebral cortex.

Question 26

Describe the somatotopic organisation of the cerebellum.

Answer 26

Guy standing on his head, then auditory/visual cortices, then guy standing upright (head/arms/legs)

Question 27

Which fibres carry all the cerebellar input information (for our purposes, at least)?

Answer 27

• Mossy fibres (from different tracts, like spinocerebellar and pontocerebellar fibres)
• Climbing fibres (remember: these are from the contra inf. olivary nucleus)

Question 28

Which cerebellar white matter nuclei get input from which parts of the cerebellum?

Answer 28

• Dentate: projections from lateral cerebellum
• Emboliform & Globose (Interposed nuclei): intermediate
• Fastigial: vermis/FN lobe

Question 29

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?

Answer 29

• 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

Question 30

Which section of the cerebellum is especially important in influencing lateral corticospinal output?

Answer 30

Intermediate; globose and emboliform (i.e. interposed) nuclei

Question 31

What do the vermis and FN lobe of the cerebellum control? Which nuclei/thalamic nuclei/cortical areas are involved? Describe the pathway.

Answer 31

• 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