Motor Systems III- Cerebellum Flashcards
What are the main features of the cerebellar cortex?
- Cerebellar cortex
- Cerebellar nuclei
- Cerebellar peduncles
inferior, middle, superior
What are the three main zones of the cerebellar cortex?
Vermis
intermediate
lateral zones
What are the cerebellar nuclei?
Fastigial
globose
emoliform
dentate
What are the three distinct cortical layers of the cerebellum?
Molecular layer
Purkinjelayer
Granular layer
What are the 5 intrinsic neurons of the cerebellar cortex and what role do they play?
1. Purkinje cells
output, inhibitory (GABA), climbing fibers
2. Granule cells
excitatory (glutamate), origin of parallel fiber system
3. Three inhibitory interneuorns
Stellate, basket and golgi cells
ALL use GABA
all excited by parallel fibers
What is the role of the purkinje cells in the cerebellar cortex?
only OUTPUT neuron
INHIBITORY (GABA) to cerebellar nuclei/vestibular nucleus
Receive parallel fiber and climbing fiber input
What are the 4 main circuits in the cerebellum?
Mossy fibers–> granule cells–> purkinje cells
Climbing fibers–> purkinje cells
Purkinje cells–> cerebellar nuclei and vestibular nucleus
Cerebellar nuclei–> targets in teh CNS
What are the two main classes of inputs to the cerebellum?
- Mossy fiber afferents:
Spinal/brianstem sites of origination–>
synapse on granule cells (Glutamate)–>
simple spkies in purkinje cells
2. Climbing fiber afferents:
Inferior olive–>
monosynaptic to Purkinje cells–>
POWERFUL excitation (all or none)–>
complex spikes in purkinje cells
What is the difference between the frequency dischage of mossy fiber and climbing fiber afferents?
Mossy fiber:
HIGH f discharge
can encode temporal/intensity information
Climbing fiber:
LOW frequency discharge
can encode “teaching signal”
Is the cerebellar cortex organized ipsilaterally or contralaterally?
IPSILATERALLY!
LEFT cerebellum controls the LEFT side of the body
RIGHT Cerebellum controls the RIGHT side of the body
What are the three functional divisions of the cerebellum?
Vestibulocerebellum
Spinocerebellum
Cerebrocerebellum
Where is the vestibulocerebellum located and what does it do?
Flocculonodular lobe and vermis
Vestibular system
Regulates balance and eye movements!
Where does input from to the vestibulorcerebellum come from?
Mossy fibers:
semicircular canals
otoliths
visual information from parietal/occipital pontine nuclei
Where does output from the vestibulocerebellum go to?
Vestibular and fastigial nuclei
Medial vestibulospinal tract–trunk/neck muscles
Lateral vestibulospinal tract–limb muscles
Gaze centers–eye movements
What are the 3 characteristics of a disorder of the cerebellum?
- Disturbances of equillibrium/balance–> fall TOWARD the side of the lesion
Test: Rhomberg
- Nystagmus
- Loss of smooth pursuit eye movements
(couldn’t follow a finger–you would see saccades)
*lesion of the fastigial nucleus has similar effects
Where is the spinocerebellum and what does it do?
Intermediate zone
Regulates body and limb movements!
What are the inputs to the spinocerebellum?
Input is via mossy fibers
- Vestibular inputs and visual/auditory
- Spinocerebellar tracts
- Face somatosensory and propioceptive inputs
What are the two examples of spinocerebellar tracts and what do they do?
1. Dorsal spinocerebellar tract
Provides peripheral feedback from cutaneous/propioceptive receptors to cerebellum
2. Ventral spinocerebellar tract
Provides information on state of spinal circuit
What is the output of the spinocerebellum?
- Vermis projects to fastigial nucleus
Reticulospinal tract
Vestibulospinal
- Intermediate zones project to globose and emboliform nuclei which project to:
Red nucleus– controls the rubrospinal tract
Ventral latearl thalamus and motor cortex- corticospinal tract
An ipsilateral lesion of the spinocerebellum would cause what deficits?
*Vermis- gait ataxia
(uncoordinated movment)
*Limb ataxia dysmetria
metrics of movement wrong (too slow too fast)
Hypotonia
Actiion/voluntary tremor
tremor as you move
Disorders of timing
Decomposition fo movements
*Lesion to the emboliform and globose nuclei ahs similar effects
Where is the cerebrocerebellum and what does it do?
Lateral hemispheres
Planning movement and evaluating sensory information for action!
What are the inputs to the cerebrocerebellum?
Inputs are via the PONTINE NUCLEI
from:
Sensory
Motor
premotor
parietal cortices
What are the outputs of the cerebrocerebellum?
via dentate nuclei
to:
Ventral lateral nucleus of the thalamus then to motor and premotor cortex
prefrontal areas
red nucleus
Disorders of the crebrocerebellum would cause….
ataxia of finest movements
cognitie deficits
There would be no paresis but you wouldn’t be able to write, hold a pen, and would have trouble with speech
The climbing fiber system arises from_________ and projects to the ______ and ___________.
What types of spikes may provide a teaching signal for learning?
Contralateral inferior olive
Purkinje cells
(is orthogonal to parallell fibers)
Complex spikes
What does the cerebellum do?
So a lesion would lead to….
Produces smooth, coordinated movments (decomposition/dysmetria)
Movement timing
Plays a role in motor learning
(LTD is the neural substrate (produced by conjunciton of climbing fiber and parallel fiber inputs ot PC)
Predicts consequences of a motor action and uses internal feedback to inform otehr brain regions
