Lec 37 Cerebellum Anatomy Flashcards
What are the main symptoms of cerebellar damage generally?
vertigo
nystagmus
ataxia
Where does cerebellum receive blood supply from?
posterior circulation –> PICA, AICA, SCA
What are the major subparts of cerebellum?
- cerebellar cortex = outer gray matter
- internal white matter
- 3 pairs of deep cerebellar nuclei in the white matter
What are the 3 pairs of cerebellar peduncles called?
superior, middle, and inferior
What is a single leaflet/convolution of cerebellum called?
folium
What comprises a lobule of cerebellum?
multiple folia
What are the 3 lobes of cerebellum?
anterior, posterior, flocculo-nodular
What does primary fissure separate?
anterior and posterior lobes
What does posterolateral fissure separate?
posterior and flocculo-nodular lobes
What info does inferior cerebellar peduncle carry?
input to cerebellum from spinal cord and medulla
What info does middle cerebellar peduncle carry?
input from pontine nuclei to cerebellum
What info does superior cerebellar peduncle carry?
all output from cerebellum [except vestibular]
input from one of tracts from spinal cord
What are the 3 deep cerebellar nuclei? their location?
fastigial = midline at vermis interposed = intermediate dentate = lateral = looks like olive
Are inputs to cerebellum excitatory or inhibitory?
all are excitatory!
What are the 4 spinocerebellar tracts?
dorsal spinocerebellar
ventral spinocerebellar
cuneocerebella
rostral spinocerebellar
Match the spinocerebellar tract with the info the give to cerebellum?
- dorsal spinocerebellar
- ventral spinocerebellar
- cuneocerebella
- rostral spinocerebellar
- lower body error signal
- upper body error signal
- lower body proprioception
- upper body proprioception
- lower body error signal
- —- ventral spinocerebellar - upper body error signal
- — rostral spinocerebellar - lower body proprioception
- —- dorsal spinocerebellar - upper body proprioception
- cuneocerebellar
What is path of lower body proprioceptive info to cerebellum?
- 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
What is path of lower body error signal to cerebellum?
- 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
What is path of upper body proprioceptive info to cerebellum?
- 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
What is path of upper body error signal to cerebellum?
- 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
What is the double cross tract? what does this mean?
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
What happens to tracts once they get to cerebellum?
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
Where does cerebellum receive cortical inputs from?
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
What is difference in location cortico-pontine fibers from frontal lobe vs non-frontal lobe regions?
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
Where does flocculo-nodular lobe receive input from?
- directly from vestibular nerve [CN 8] and from vestibular nuclei
- imp for posture, balance, eye movement, control functions
What is path of internal processing in cerebellum?
- inputs received by cerebellar cortex
- cerebellar cortex projects to deep cerebellar nuclei
- deep cerebellar nuclei project to thalamus, red nuc, or vestibular nuc
What are two type os input to cerebellum?
climbing fibers [from inferior olivary complex]
mossy fibers [from most other places]
What is difference mossy vs climbing fibers?
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
What are the 3 layers of cerebellar cortex?
- molecular [closest to pit]
- purkinje
- granule
What is contained in the molecular layer?
- dendrites of purkinje cells = perpendicular to long axis of folium
- cell bodies of inhibitory interneurons [stellate + basket]
What is difference stellate vs basket cells in cerebellum?
stellate = inhibit purkinje dendrites basket = inhibit purkinje cell bodies
What is contained in the purkinje layer?
cell bodies of purkinje cells
What is contained in the granule layer?
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
Where do purkinje cells project?
GABA inhibitory to deep cerebellar nuclei
vermis/flocculonodular cells –> fastigial nuclei
intermediate –> interposed nuclei
lateral hemispheres –> dentate nuclei
Where do vermis purkinje cells project?
to fastigial nuclei
Where do intermediate zone purkinje cells project?
interposed nuclei
Where do lateral hemisphere purkinje cells project?
dentate nuclei
What is output path of cerebellar control of posture?
flocculonodular/vermis purkinjes –> fastigial nucleus –> vestibular nuclei of brainstem [bilateral] –> reticulospinal/vestibulospinal tracts –> axial/neck muscles
What is output path of cerebellar control of motor control?
paravermis purkinjes –> interposed nuclei –> superior cerebellar peduncle [crosses] –> contralateral red nucleus –> rubro-olivary and rubrospinal tracts
What is output path of cerebellar control of motor planning?
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
What is function of red nucleus in cerebellar relay?
- receives input from contralateral interposed nuclei and dentate nuclei via superior cerebellar peduncle
- integrates info from paravermal intermediate zone and lateral hemispheres of cerebellum
What is function of vestibular output from cerebellum?
- control of eye movement and axial/girdle muscles via vestibulo-spinal tracst
Why are cerebellar symptoms always ipsilateral to site of damage?
- 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
