CEREBELLUM Flashcards
what does the cerebellum do?
modulates movement
detects motor error and provide corrections to improve performance
ipsilateral or contralateral
ipsilateral side
cerebellum is joined to brainstem by
cerebral peduncles
superior peduncle
- ->midbrain (brachium conjunctivum)
- ->red nucleus OR–>thalamus (VL, VA)
output (decussates!)
middle peduncle
–>pons (brachium pontis)
input
inferior peduncle
–>medulla & spinal cord (restiform body)
input & output
what passes through inferior peduncle
vestibular nere & nucleus
what are the hemispheres of cerebellum separated by
vermis
fissures of cerebellum
- primary fissure (ant/post)
- posterolateral (posterior/flocculonodular)
where is the tonsil lobule located?
superior to foramen magnum
what happens if intracranial pressure increases in tonsil lobule?
tonsil herniates downward through foramen magnum–>compresses respiratory centers in medulla and spinal cord
spinocerebellum parts
vermis
intermediate zone
fx of spinocerebellum
- receives information from spinal cord
- regulates muscle tone and adjusts ongoing movements
fx cerebrocerebellum
- receives info from cerebral cortex
- planning and initiating skilled movements
- mostly associated with cognitive functions
vestibulocerebellum components
aka flocculonodular lobe
–floculus and nodulus
fx vestibulocerebellum
-stabilization of eyes during head movement
nuclei from medial to lateral
fastigial
interposed
dendate nucleui
fastigial nuclei receive input form
purkinji cells of vermis
interposed receive input from
intermediate zone
globose and emboliform
dendate nuclei receive input from
lateral hemispheres
what is special about dendate nuclei
biggest output!
transverses superior cerebellar peduncle and decussates in midbrain
5 types of cells in cerebellar cortex
purkinji cells granule cells golgi cells basket cells stellate cells
3 layers of cerebellar cortex
molecular- scarce neurons
purkinji- single layer large cells
granule cells- lots of neurons
what is the only type of cell that doesnt use GABA?
granule cell
purkinji cells
only output from cerebellar cortex
–terminates in deep cerebellar nuclei or vestibular nucleus
where are purkinji axons
white matter
granule cells
axons are in the molecular layer (called parallel fibers)–>synapse on dendrites of purkinji to excite
2 input to cerebellum
mossy fibers
climbing fibers
mossy fibers are
axons coming from other parts of the brain to terminate
–>a single mossy fiber excites thousands of granule cells
pathway of cerebellum input
cerebral cortex —corticopontine fibers–>pons–pontocerebellar fibers–>mossy fibers in cerebellar cortex –>excite granule cells –>excite parallel fibers –>input to purkinji cells
climbing fibers are
axons that extend up purkinji (climb it)
–arise from inferior olivary nucleus and connect to one or two purkinji
climbing fiber vs granule cell
single Ap from climbing–>dozen AP from purkinji
many act II fibers–>1 purkinje response
how many parallel fibers per purkinji?
100–>300,000
inhibitory sculpting
outputs from cerebellum is shaped by inhibiting continuous activity
plasticity
synapses between parallel fibers and purkinji cells are plastic–>changes lead to short term error correcton and long term motor learning
long term vs short term plasticity
short term- few minutes or less; local inhibition or error correction
long term- greater than 30 mins
upregulation or downregulation of synthesis or trafficking of R in membrane
II fibers excitation mech
glutaminergic –>acts on AMPA R and metabotrophic glutamate R–>DAG & IP3
climbing fibers excite mech
activated when motor performance is not meeting expectation
–>aspartate is excite NT–>opens Ca channels and excites purkinji cell
together II and climbing (long term synaptic dpression)
activate protein kinase C–>phos AMPA R (decrease efficacy in short term) & internalize ampa R–>dec response to activated synapse in future
**allows cerebellum to change output next time similar circumstances occur
main job of vestibulocerebellum
tells about state of body eq
input Vestibulocerebellum pathway
vestibular apparatus of internal ear (cristae, maculae, vestibular nuclei of brainstem)–> inf cerebellar peduncle–> ipsilateral–>terminate as mossy fibers
output vestibulocerebellum
purkinji cell axon–>inf cerebellar peduncle–>termiante in vestibular nuclei–>spinal cord to go to extraoccular nuclei and other muscles
regulation of postural movements to main eq and muscle tone
spinocerebellum
receives input from spinal cord and adjusts ongoing movements to control muscle tone
*proprioceptive from ipsilateral side
visual and aud compliment prioprioceptive information
spinocer. input
spinocerebellar pathways (dorsal: lower limb vs cuneocerebellar: upper limb)–> inferior cerebellar peduncle
termination of spinocer. input
trunk: vermis
limb: internal zone
output of spinocer comes from 2 places
vermis
intermediate zone
vermis output
ipsilateral fastigial nucleus
–>inf cerebellar peduncle–>brainstem bilaterally including vestibular nuclei and reticular formation
OR
–>motor cortex (via thal)–>ventral cortciospinal tract & corticobulbar tract
ventral cortcospinal tract fx
axial muscles
corticobulbar tract fx
facial/tongue muscles
vestibular nuclei & resticular formation projection fx
influences descending pathways that control axial muscles via vestibulospinal and reticulospinal tract
intermediate zone output
ipsilateral interposed nuclei
–>red nucleus
OR–>superior cerebellar peduncle (decussate)–>motor cortex (decussate again)–>lateral cortcospinal and rubrospinal tracts to limb muscles
**ipsilateral due to double crossover
cerebrocerebellum
planning, learning, and initiating (high-skilled) voluntary motor sequence
input cerebrocerebellum
cerebral cortex –corticopontine tract–>ipsilateral to pontine nucleus–>traverse pontine fibers–>DECUSSATE in pons–.enter middle cerebellar peduncle–>contralateral cerebellum
output cerebrocerebellum
purkinji axons–>ips dentate nucleus–>sup cerebellar peduncle (decussate)–>VL thalamus OR red nucleus
output cerebro from red nucleus
midbrain–dentatorubral fibers–>rednucleus (parvocellular division)–>ipsilateral inferior olive–>climbing fibers–>cross over and enter inferior cerebellar peduncle–>purkinje
*controlateral
output from VL of thalamus
motor and premotor cortices via dentothalamic fibers
**usually ipsilateral because crossover in corticospinal and cortciobulbar
