Cerebellum

Question 1

Describe the inputs to the cerebellum.

Answer 1

Afferent information:
vestibular
proprioceptive and skin receptor information
sensorimotor cortex (auditory system and visual system)

Question 2

Describe in a broad sense the information processing of the cerebellar cortex and nuclei.

Answer 2

mossy and climbing fibers enter the cerebellar cortex …almost all info exits through Purkinje cells (which left alone have an inhibitory function) and they project to deep nuclei.

Question 3

What is the overall role of the cerebellum.

Answer 3

coordination

correction of current movements to match those intended

Question 4

Describe the outputs of the cerebellum.

Answer 4

Motor systems:
vestibular nucleus 
thalamus
red nucleus 
(reticular formation)
NO DIRECT connection to the spinal cord

Question 5

Describe the gross anatomy of the cerebellum.

Answer 5

Superior cerebellar peduncle (carrying info OUT)
Middle cerebellar peduncle (inferior and middle are carrying information mostly IN)
Inferior cerebellar peduncle

most of neurons in brain are in the cerebellum…TONS of processing taking place

sort of like a roof over the 4th ventricle

Vermis (anterior lobe)
Hemisphere (posterior lobe)
flocculus and nodulus …. damage to one section produces different clinical findings

Question 6

Describe the afferents to the cerebellum. What are they called?

Answer 6

from cerebral cortex to pontine nuclei, pontocerebellar fibers will go through MCP and enter the cerebellar cortex (L cerebral cortex projects to right cerebellum)

afferent info coming from inferior olive, vestibular cochlear nuclei and DSCT and CCT to ICP and then cerebellar cortex

(all fibers coming in (afferent) are called “mossy” because of which neurons they will innervate in the cerebellum/where they end up except ONE - “climbing” fibers originates from inferior olive

Question 7

Describe the somatotopic anatomy of the cerebellum.

Answer 7

midline (vermis) has to do with trunk movement (gait/balance) - projects to fastigal nucleus

hemispheres - have to do with activity of limbs (project to dentate nucleus)

flocconodular- vestibular eye movement

Question 8

Where might there be a problem if someone has issues with their hand or leg on their right side of body?

Where might there be a problem if someone exhibits difficulty walking?

Answer 8

cerebellar function on RIGHT side of body

(SAME SIDE)

walking problem- cerebellar vermis

Question 9

What do Perkinje cells do?

Answer 9

Info is mainly in hemispheres and Purkinje projects out to deep nuclei. Purkinje tend to inhibit these deep cerebellar nuclei

Question 10

Describe the ICP afferents/efferents.

Answer 10

Afferents: inferior olivary nucleus (medulla), vestibular nuclei, spinal cord, trigeminal nucli, reticular formation

Cerebellar efferents:
vestibular nuclei

Question 11

Decribe MCP afferents/efferents.

Answer 11

Afferents: cerebral cortex
No efferents

Cortex projects down to pontine nuclei which then cross over to cerebellum on the other side

Question 12

Describe the main/notable afferents to the cerebellum. (Specific names)

Answer 12

Anterior spinocerebellar ascends in contralateral spinal cord (T12-L5) and terminates in vermis and intermediate zone - ipsilateral (SCP)

Pontocerebellar originates from pontine nuclei and terminates in anterior and posterior lobes - contralateral vermis - ipsilateral (ONLY ONE GOING THROUGH MCP)
-middle takes care of cortex

almost ALL come from the ICP

Question 13

Describe the SCP afferents/efferents.

Answer 13

Afferents:
anterior spinocerebellar tract

Cerebellar efferents:
originate from deep cerebellar nuclei

-info with SCP crosses to the other side (cerebral cortex projects: L controls R side of body)

Question 14

Describe what would happen with a lesion of R cerebellar or R cerebral cortex.

Answer 14

R cerebellar lesion - problem with R side of body

R cerebral lesion - problem w L side of body

Question 15

Describe/diagram the flocculonodular lobe (input and output).

What are the clinical findings when it is damaged?

Answer 15

See diagram on slide 19.

(if problem there will be balance and coordination problems associated with the head - can affect eye movement, shaking eyes)

Question 16

Describe/diagram the vermis (input and output).

What are the clinical findings when it is damaged?

Answer 16

See diagram on slide 20.

clinical findings: damage to vermis can result in walking with feet apart, can’t keep balance when sitting

Question 17

Describe/diagram the cerebellar hemispheres (input and output).

Answer 17

See digram on slide 21.

lesion produce motor coordination problems with limbs (arm or leg may be uncoordinated)

Question 18

Describe the layers of the cerebellum.

Answer 18

3 layers
molecular layer (outermost)
Purkinje cell layer (middle)
granular layer (inner layer)

Question 19

Describe the molecular layer of the cerebellum.

Answer 19

mainly axons and dendrites (outermost layer)

Basket cells - axons synapse on the Purkinje cell body
Stellate cells - axons synapse on Purkinje cell dendrites

Question 20

Describe the Purkinje cell layer.

Answer 20

middle layer

Purkinje cells- ONLY axons that leave the cerebellar cortex (major efferents!)

Question 21

Describe the granular layer.

Answer 21

innermost layer before the white matter

Granular cells - send their axons into the molecular layer as parallel fibers (where all mossy fibers synapse)

Question 22

Describe the functions and pathways of mossy fibers, climbing fibers, Purkinje cells.

Answer 22

mossy fibers synapse on granule cells and send long projections to granule layer, split into parallel fibers that go both ways and will interact with the dendrites of Purkinje cells. (if activate one parallel, minimal effect … can have thousands of parallel fibers per Purkinje)
-granule sends cell axon to molecular layer to divide up into a parallel fiber - it is excitatory exciting inhibition of Purkinje cell

Climbing fibers from contralateral inf. olivary nucleus will wrap around dendritic tree of Purkinje cells (have a 1:1 ratio with Purkinje cells… VERY specific, if activate one, SIGNIFICANT effect)
- climbing wraps around dendritic tree so when its turned on it REALLY turns on the inhibitory function of that one Purkinje cell.

satellite cells inhibit inhibition

Question 23

Describe the dendritic tree.

Answer 23

You have a granule cell shooting up parallel fibers through rows of Purkinje cells lined up ( can have 1 axon with over 400 Purkinje cells lined up) … but have thousands of parallel fibers going through - so takes a bunch of granule cells to be activated to have an effect

Question 24

Cerebellar diseases generally cause 3 principal deficits. Describe them.

Answer 24

1. HYPOTONIA: diminished resistance to passive limb displacement, often called “lack of check”; results in overshooting and excessive rebound.


2. ATAXIA: delay in the initiation of movement, errors in range and force of movements (dysmetria) and errors in the regularity and rate of repetitive movements (dysdiadochokinesia).


3. INTENTION TREMOR: errors in position; most marked at the end of movements where the greatest precision is required.