Lec 37 Cerebellum Anatomy

Question 1

What are the main symptoms of cerebellar damage generally?

Answer 1

vertigo
nystagmus
ataxia

Question 2

Where does cerebellum receive blood supply from?

Answer 2

posterior circulation –> PICA, AICA, SCA

Question 3

What are the major subparts of cerebellum?

Answer 3

• cerebellar cortex = outer gray matter
• internal white matter
• 3 pairs of deep cerebellar nuclei in the white matter

Question 4

What are the 3 pairs of cerebellar peduncles called?

Answer 4

superior, middle, and inferior

Question 5

What is a single leaflet/convolution of cerebellum called?

Answer 5

folium

Question 6

What comprises a lobule of cerebellum?

Answer 6

multiple folia

Question 7

What are the 3 lobes of cerebellum?

Answer 7

anterior, posterior, flocculo-nodular

Question 8

What does primary fissure separate?

Answer 8

anterior and posterior lobes

Question 9

What does posterolateral fissure separate?

Answer 9

posterior and flocculo-nodular lobes

Question 10

What info does inferior cerebellar peduncle carry?

Answer 10

input to cerebellum from spinal cord and medulla

Question 11

What info does middle cerebellar peduncle carry?

Answer 11

input from pontine nuclei to cerebellum

Question 12

What info does superior cerebellar peduncle carry?

Answer 12

all output from cerebellum [except vestibular]

input from one of tracts from spinal cord

Question 13

What are the 3 deep cerebellar nuclei? their location?

Answer 13

fastigial = midline at vermis
interposed = intermediate
dentate = lateral = looks like olive

Question 14

Are inputs to cerebellum excitatory or inhibitory?

Answer 14

all are excitatory!

Question 15

What are the 4 spinocerebellar tracts?

Answer 15

dorsal spinocerebellar
ventral spinocerebellar
cuneocerebella
rostral spinocerebellar

Question 16

Match the spinocerebellar tract with the info the give to cerebellum?

• dorsal spinocerebellar
• ventral spinocerebellar
• cuneocerebella
• rostral spinocerebellar

1. lower body error signal
2. upper body error signal
3. lower body proprioception
4. upper body proprioception

Answer 16

1. lower body error signal
   - —- ventral spinocerebellar
2. upper body error signal
   - — rostral spinocerebellar
3. lower body proprioception
   - —- dorsal spinocerebellar
4. upper body proprioception
   - cuneocerebellar

Question 17

What is path of lower body proprioceptive info to cerebellum?

Answer 17

• muscle spindle afferents [1a] ascend in gracile fasciculus in dorsal column to synapse in clarke’s nucleus in thoracic spinal cord
• 2ndary neurons of clark’s nuclus form dorsal spinocerebellar tract and ascend more laterally to enter cerebellum via ipsilateral inferior cerebellar peduncle

== does not cross midline

Question 18

What is path of lower body error signal to cerebellum?

Answer 18

• GTO afferents [1b] carry info to spinal cord interneurons
• interneurons compare sensory to descending motor commands to generate error signal + convey discrepancy between motor plan and executed movement
• interneuron axons for ventral spinocerebellar tract –> cross spinal cord in anterior white commissure –> ascend on contralateral lateral spinal cord
• join superior cerebellar peduncle and re-cross the midline to go back to side of origin = double cross track

Question 19

What is path of upper body proprioceptive info to cerebellum?

Answer 19

• muscle spindle afferents [1a] ascend in fasciculus cuneatus in dorsal column
• terminate in lateral cuneate nucleus
• form cuneocerebellar tract
• travel through ipsilateral inferior cerebellar peduncle

Question 20

What is path of upper body error signal to cerebellum?

Answer 20

• afferents from GTO [1b] enter spinal cord and synapses on interneurons then ascend ipsilaterally as rostral spinocerebellar tract
• goes through ipsilateral inferior cerebellar peduncle to enter cerebellum

Question 21

What is the double cross tract? what does this mean?

Answer 21

ventral spinocerebellar tract [lower body error signal]

• info crosses midline in spinal cord, ascends contralaterally, and crosses back in superior cerebellar peduncle to enter cerebellum

Question 22

What happens to tracts once they get to cerebellum?

Answer 22

terminate topographically
together with trigeminal inputs create several somatotopic representations of head and body in cerebellar cortex [most complete = anterior and posterior lobe]

axial = vermis; distal [limbs] = intermediate zone

Question 23

Where does cerebellum receive cortical inputs from?

Answer 23

indirectly through massive relay in pontine nuclei = reticular formation

cerebral cortex –> ipsilateral pontine nucleus –> cerebral peduncle –> cross with crossing fibers of pons –> form middle cerebellar peduncle on contralateral side –> terminate in lateral hemisphere of cerebellum

end of in hemisphere of cerebellum contralateral to where they started in cortex

Question 24

What is difference in location cortico-pontine fibers from frontal lobe vs non-frontal lobe regions?

Answer 24

frontal = pass through anterior limb of internal capsule –> course more medially in cerebral peduncle

non-frontal = pass through posterior limb of IC –> more lateral in cerebral peduncle

Question 25

Where does flocculo-nodular lobe receive input from?

Answer 25

- directly from vestibular nerve [CN 8] and from vestibular nuclei - imp for posture, balance, eye movement, control functions

Question 26

What is path of internal processing in cerebellum?

Answer 26

1. inputs received by cerebellar cortex 2. cerebellar cortex projects to deep cerebellar nuclei 3. deep cerebellar nuclei project to thalamus, red nuc, or vestibular nuc

Question 27

What are two type os input to cerebellum?

Answer 27

climbing fibers [from inferior olivary complex] mossy fibers [from most other places]

Question 28

What is difference mossy vs climbing fibers?

Answer 28

mossy = indirect input to purkinje cells; relayred via parallel granule cell fibers; distributed excitation = granule cells convey mossy fiber info to large number of purkinje cells climbing: convergent excitation = 1 purkinje gets input from 1 climbing; direct synapse onto purkinje cells; from inferior olivary complex only

Question 29

What are the 3 layers of cerebellar cortex?

Answer 29

- molecular [closest to pit] - purkinje - granule

Question 30

What is contained in the molecular layer?

Answer 30

- dendrites of purkinje cells = perpendicular to long axis of folium - cell bodies of inhibitory interneurons [stellate + basket]

Question 31

What is difference stellate vs basket cells in cerebellum?

Answer 31

``` stellate = inhibit purkinje dendrites basket = inhibit purkinje cell bodies ```

Question 32

What is contained in the purkinje layer?

Answer 32

cell bodies of purkinje cells

Question 33

What is contained in the granule layer?

Answer 33

golgi cells = inhibitory interneurons granule cells = excitatory --> project to molecular layer and bifurcate to form parallel fibers along axis of folium to excite many purkinje cell dendrites at once

Question 34

Where do purkinje cells project?

Answer 34

GABA inhibitory to deep cerebellar nuclei vermis/flocculonodular cells --> fastigial nuclei intermediate --> interposed nuclei lateral hemispheres --> dentate nuclei

Question 35

Where do vermis purkinje cells project?

Answer 35

to fastigial nuclei

Question 36

Where do intermediate zone purkinje cells project?

Answer 36

interposed nuclei

Question 37

Where do lateral hemisphere purkinje cells project?

Answer 37

dentate nuclei

Question 38

What is output path of cerebellar control of posture?

Answer 38

flocculonodular/vermis purkinjes --> fastigial nucleus --> vestibular nuclei of brainstem [bilateral] --> reticulospinal/vestibulospinal tracts --> axial/neck muscles

Question 39

What is output path of cerebellar control of motor control?

Answer 39

paravermis purkinjes --> interposed nuclei --> superior cerebellar peduncle [crosses] --> contralateral red nucleus --> rubro-olivary and rubrospinal tracts

Question 40

What is output path of cerebellar control of motor planning?

Answer 40

lateral hemisphere purkinjes --> dentate nuclei --> superior cerebellar peduncle [crosses] --> joins thalamic fasciculus --> thalamus [VLp] --> cerebral cortex --> distal musculature via corticospinal *dentate nuclei also project to red nucleus

Question 41

What is function of red nucleus in cerebellar relay?

Answer 41

- receives input from contralateral interposed nuclei and dentate nuclei via superior cerebellar peduncle - integrates info from paravermal intermediate zone and lateral hemispheres of cerebellum

Question 42

What is function of vestibular output from cerebellum?

Answer 42

- control of eye movement and axial/girdle muscles via vestibulo-spinal tracst

Question 43

Why are cerebellar symptoms always ipsilateral to site of damage?

Answer 43

- all outputs except vestibular cross in superior cerebellar peduncle - target structs [red nucleus + cerebral cortex via thalamus] then give rise to descending motor tracts that cross = second crossing as a result final descending motor fibers are ipsilateral to initial cerebellar fibers