Cerebellum [3] Flashcards
- Source of input
- where is output going
- info/fxn being carried?
- where do input/outputs cross midline?
Cerebellum lab
Cerebellar deficits: 1 of 3 possible
- equilibrium
- tone
- synergy
(no loss of sensation or muscle strength)
Major cerebellar inputs
Outputs?
INputs:
- inferior and middle peduncles
Outputs:
- superior peduncle
Flocculonodular lobe, aka
vestibulocerebellum
- receives input from vestibular organs
- outputs to vestibular nucleus in brainstem
Paleocerebellum aka
spinocerebellum( vermal and paravermal cortex) - midportion of the anterior and posterior lobe
- recieves input from spinal afferents
- outputs onto motor control nuclei
neocerebellum aka
corticocerebellum/cerebrocerebellum
- lateral lobes or hemispheres
Efferents from the vermis project to ___
Efferents from the paravermis project to ____
Efferents from the cerebrocerebellum (lat hemis) to ___
fastigial nucleus
interposed nucleus (red nucleus via IN)
dentate
Afferents to the vermis arise from ____
Afferents to the paravermis arise from ____
Afferents to the cerebrocerebellum (lat hemis) arise from ____
multiple sources
spinal cord
pontine gray matter
All cerebellar regions (vermis, paravermis, cerebrocerebellum) receive climbing fiber innervation from the _________
contralateral inferior olivary nucleus
fastigial nucleus → vermis involved in control of what?
axial/core musculature
posture/balance/equilibrium
integration of head/eye movements
interposed nucleus → paravermis involved in control of what?
fine tunes movement of limbs
distal muscles
dentate → lateral hemispheres involved in control of what?
higher level coordination of mvements
(planning/initiation)
- finger nose fingerVO
__________ supplies innervation/connections to the flocculo-nodular lobe
vestibular nucleus of the brain (insteadof the deep nuclei like vermis, paravermis, and lateral hemis)
_________ supplies the major output pathways of the cerebellum.
deep nuclei (fastigial nucleus interposed nucleus dentate)
fastigial nucleus sends info to which structures?
(bilaterally)
- vestibular nucleus → vestibulospinal tract
- pontine reticular formation → pontine reticulospinal tract
Significance of no somatotopic map in the lateral hemispheres
majority of info to the cerebellum from the cortex is by way of the pontine nucleu and to the lateral zone
Deep nuclei of spinocerebellum
Fastigial (vermis)
Interposed (paravermal)
Cerebellar deficits are always ips/contra lateral
What about tracts between cerebellum and cortex?
Ipsilateral
- input and descending outputs largely uncrossedracts
Tracts normally dessucate
Cerebellar lesions result in loss of _______ but no loss of _______
coordination/equil
sensation or muscle strength
What type of cerebellar lesion results in motor effects?
Large regions of the cortex involved or underlying deep nuclei
If flocculo-nodular lobe is impaired, ______ is impaired, but not _______
equilibrium impaired
Coord and muscle tone not impaired
Vermal degeneration in alcoholism leads to _______
postural problems, locomotion, gaze
see cerebellar lesion, think _________
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)
Information flow to the cerebellar cortex comes in through which fibers?
- mossy fibers (from variety of sources)
- climbing fibers (from contralateral inferior olivary nucleus
both are the main afferents of to the cerebellar cortex + excite purkinje fibers
With the exception of granule cells, all cerebellar cortical neurons including purkinje cells, make _____ synaptic conxns with their target neurons.
inhibitory
granule cells branch T and form excitatory synapse on purkinje cells and interneurons (stellate and basket cells)
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.
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
The only output from the cerebellar cortex is via _____
purkinje cells
which is inhibitory on the deep nuclei
Why do the deep nuclei receive both excitatory and inhibitory inputs?
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
Inhibitory interneurons w/in cerebellar cortex
- basket
- stellate cells
- both interneurons inhibit neighboring purkinje cells (inhibiting an inhibitor = disinhibition of deep cerebellar neurons)
purkinje cells have a high rate of spontaneous activity, meaning what?
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
VOR and what a lesion in the flocculonodular lobe does
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
What detects a discrepancy between planned and actual motor performance? How does it modulate cerebellar activity?
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
