Cerebellum

Question 1

Cerebellum function

Answer 1

In voluntary movement

In posture and equilibrium

Primarily inhibitory function

Question 2

What percentage of the brain’s neurons does the cerebellum have

Answer 2

Consists of ~10% gross brain volume but is highly convoluted and contains >50% of the brain’s neurons.

Question 3

Cerebellar inputs and outputs

Answer 3

The cerebellum operates in 3’s:
there are 3 main inputs
there are 3 main outputs from 3 deep nuclei.

The 3 routes are the peduncles, or “stalks” - the rostral, middle and caudal cerebellar peduncles.

Question 4

Cerebellar peduncles

Answer 4

Cerebellar peduncles carry axons into and out of the cerebellum
One pair (cranial): out of cerebellum (Efferent)
2 pairs: (middle & caudal): afferent to cerebellum.

Question 5

Inputs of the cerebellum

Answer 5

The inputs are:
Mossy fibers from:
Corticopontocerebellar pathway
Spinocerebellar pathways
Reticular nuclei (brainstem)
Vestibular nuclei (brainstem)
Climbing fibers from the inferior olive of medulla

Question 6

Cerebellar Afferent pathways

Question 7

Cerebellar circuits

Answer 7

Three layers and only 5 types of neurons throughout the cerebellar cortex:

Stellate cells: inhib.
Basket cells: inhib.
Golgi cells: inhib.
Granule cells: excit
Purkinje cells: inhib.

Question 8

The 3 layers of the cerebellum

Answer 8

Molecular layer
Purkinje cell layer
Granule cell layer

Question 9

Molecular layer

Answer 9

Outermost (molecular layer) consists primarily
- granule cell axons, known as parallel fibers;

-dendrites of neurons located in deeper layers

-scattered inhibitory interneurons: (the stellate and basket cells)

Question 10

The primary input fiber axons to cerebellum

Answer 10

Climbing fiber: from medulla

Mossy fiber: from higher brain, brainstem and spinal cord

Question 11

Mossy fibers and climbing fibers

Answer 11

Directly excite cerebellar nuclei neurons, or their inputs can be integrated to affect Purkinje cell response

Question 12

Input/output organization of the cerebellum:

Answer 12

Normally, effect of interaction slightly favors excitation of deep nuclei; hence, there is continuous moderate stimulation of deep nuclei

Question 13

The three deep nuclei of the cerebellum

Answer 13

The 3 deep nuclei are:
1. Vermis–> Fastigial–>vestibular and reticular nuclei

2. Lateral zone–>Dentate–>thalamus, red nucleus, cerebral cortex

3.Intermediate–>Interposed–>thalamus and red nucleus

All 3 receive inputs from sensory afferent tracts and from the cerebellar cortex.

Question 14

Fastigial

Answer 14

Concerned with balance; sends information mainly to the vestibular and reticular nuclei

Question 15

Dentate and Interposed nucleus

Answer 15

Both concerned with voluntary movement; send axons mainly to the thalamus and red nucleus

Question 16

Major efferent pathways

Answer 16

To medullary and pontine regions of the brainstem – posture and equilibrium

To thalamus , cortex, basal ganglia, red nucleus, & reticular formation – coordination between agonists and antagonists

To thalamus , cortex – coordination of sequential motor actions

Question 17

Vestibulocerebellum

Answer 17

Helps coordinate balance and eye movement

Pathway:
1. either body or head movement
2. Vestibular sensory (inner ear)
3. Flocculonodular (cerebellum)
4. Vestibular motor (brain stem)
5. alpha and gamma motor neurons (brainstem and spinal cord)
6. Muscle tone & head movement with eye position

Question 18

Spinocerebellum

Answer 18

Helps coordinate muscle tone + limb movement

Question 19

Cerebrocerebellum

Answer 19

Helps with planning coordinated, properly timed movement sequences