Cerebellum [3]

Question 1

1. Source of input
2. where is output going
3. info/fxn being carried?
4. where do input/outputs cross midline?

Answer 1

Cerebellum lab

Question 2

Cerebellar deficits: 1 of 3 possible

Answer 2

1. equilibrium
2. tone
3. synergy

(no loss of sensation or muscle strength)

Question 3

Major cerebellar inputs

Outputs?

Answer 3

INputs:
- inferior and middle peduncles

Outputs:
- superior peduncle

Question 4

Flocculonodular lobe, aka

Answer 4

vestibulocerebellum

• receives input from vestibular organs
• outputs to vestibular nucleus in brainstem

Question 5

Paleocerebellum aka

Answer 5

spinocerebellum( vermal and paravermal cortex) - midportion of the anterior and posterior lobe

• recieves input from spinal afferents
• outputs onto motor control nuclei

Question 6

neocerebellum aka

Answer 6

corticocerebellum/cerebrocerebellum

• lateral lobes or hemispheres

Question 7

Efferents from the vermis project to ___
Efferents from the paravermis project to ____
Efferents from the cerebrocerebellum (lat hemis) to ___

Answer 7

fastigial nucleus
interposed nucleus (red nucleus via IN)
dentate

Question 8

Afferents to the vermis arise from ____
Afferents to the paravermis arise from ____
Afferents to the cerebrocerebellum (lat hemis) arise from ____

Answer 8

multiple sources
spinal cord
pontine gray matter

Question 9

All cerebellar regions (vermis, paravermis, cerebrocerebellum) receive climbing fiber innervation from the _________

Answer 9

contralateral inferior olivary nucleus

Question 10

fastigial nucleus → vermis involved in control of what?

Answer 10

axial/core musculature
posture/balance/equilibrium
integration of head/eye movements

Question 11

interposed nucleus → paravermis involved in control of what?

Answer 11

fine tunes movement of limbs

distal muscles

Question 12

dentate → lateral hemispheres involved in control of what?

Answer 12

higher level coordination of mvements
(planning/initiation)
- finger nose fingerVO

Question 13

__________ supplies innervation/connections to the flocculo-nodular lobe

Answer 13

vestibular nucleus of the brain (insteadof the deep nuclei like vermis, paravermis, and lateral hemis)

Question 14

_________ supplies the major output pathways of the cerebellum.

Answer 14

deep nuclei (fastigial nucleus 
interposed nucleus
dentate)

Question 15

fastigial nucleus sends info to which structures?

Answer 15

(bilaterally)

1. vestibular nucleus → vestibulospinal tract
2. pontine reticular formation → pontine reticulospinal tract

Question 16

Significance of no somatotopic map in the lateral hemispheres

Answer 16

majority of info to the cerebellum from the cortex is by way of the pontine nucleu and to the lateral zone

Question 17

Deep nuclei of spinocerebellum

Answer 17

Fastigial (vermis)

Interposed (paravermal)

Question 18

Cerebellar deficits are always ips/contra lateral

What about tracts between cerebellum and cortex?

Answer 18

Ipsilateral
- input and descending outputs largely uncrossedracts

Tracts normally dessucate

Question 19

Cerebellar lesions result in loss of _______ but no loss of _______

Answer 19

coordination/equil

sensation or muscle strength

Question 20

What type of cerebellar lesion results in motor effects?

Answer 20

Large regions of the cortex involved or underlying deep nuclei

Question 21

If flocculo-nodular lobe is impaired, ______ is impaired, but not _______

Answer 21

equilibrium impaired

Coord and muscle tone not impaired

Question 22

Vermal degeneration in alcoholism leads to _______

Answer 22

postural problems, locomotion, gaze

Question 23

see cerebellar lesion, think _________

Answer 23

HANDS Tremor
Hypotonia (ant. lobe injury)
Ataxia
- dysdiadochokinesia
- decomposition of movement
- dysmetria/past pointing
Nystagmus
Dysarthria
Stance/gait prob

Tremor (intention tremor - worse closer you get to target)

Question 24

Information flow to the cerebellar cortex comes in through which fibers?

Answer 24

1. mossy fibers (from variety of sources)
2. climbing fibers (from contralateral inferior olivary nucleus

both are the main afferents of to the cerebellar cortex + excite purkinje fibers

Question 25

With the exception of granule cells, all cerebellar cortical neurons including purkinje cells, make _____ synaptic conxns with their target neurons.

Answer 25

inhibitory

granule cells branch T and form excitatory synapse on purkinje cells and interneurons (stellate and basket cells)

Question 26

Activation of a climbing fiber will produce a _______ response in the purkinje cells it innervates. Activation of a parallel fiber will induce a _____ in the purkinje cell it innervates.

Answer 26

Climbing fiber: complex spike

• 1 climbing fiber: 1 purkinje cells
• single powerful AP → burst of spikes in purkinje cells

Parallel fiber: simple

• many parallel:purkinje
• parallel sum to generate a single action potential

Purkinje cell output is inhibitory on cells of deep nuclei

Question 27

The only output from the cerebellar cortex is via _____

Answer 27

purkinje cells

which is inhibitory on the deep nuclei

Question 28

Why do the deep nuclei receive both excitatory and inhibitory inputs?

Answer 28

Excitatory from mossy and climbing fibers
Inhibitory from purkinje fibers
- cerebellum is a inhibitory delay loop, with action in shaping the timing of descending motor commands
- synaptic plasticity occurs

Question 29

Inhibitory interneurons w/in cerebellar cortex

Answer 29

1. basket
2. stellate cells

• both interneurons inhibit neighboring purkinje cells (inhibiting an inhibitor = disinhibition of deep cerebellar neurons)

Question 30

purkinje cells have a high rate of spontaneous activity, meaning what?

Answer 30

they generate action potential even without excitatory inputs (like cells in globus pallidus)
→ purkinje cells are continually suppressing activity of deep cerebellar neurons

• basket and stellate cells on purkinje cells will release deep cerebellar neurons from inhibitions

Question 31

VOR and what a lesion in the flocculonodular lobe does

Answer 31

VOR involves influence of semi-circular canals on extraocular muscles to preserve constancy of visual field during head movements

• very dependent on cerebellum
• lesion of flocculonodular lobe means adaptation/learning does not take place

Question 32

What detects a discrepancy between planned and actual motor performance? How does it modulate cerebellar activity?

Answer 32

the inferior olive detects discrepancy →
generates climbing fiber activity (error signal) →

modulates cerebellar fxn (including long term depression of sensitivity to mossy fiber)

• people with inferior olivary lesions are unable to adapt/learn