Lab 8.2: Cerebellar Pathways

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What are the first order neurons of the DSCT? Where do they synapse with second order neurons?: *primary afferents from the limbs, usually 1-A neurons
*synapse with second order neurons in Clarke's nucleus in the gray matter of the spinal cord between L2 and C8
Where is Clarke's nucleus located? What neurons synapse here?: In the gray matter of the spinal cord between L2 and C8. First order neurons of the DSCT synpase with second order neurons of the same tract.
Where in the spinal cord does the DSCT run?: On the lateral margins, ventral to the dorsal horns.
How do do second order neurons of the DSCT enter the cerebellum? Where do these neurons synapse?: They enter through the ICP and synapse on Purkinje cells in the spinocerebellar cortex; there are some direct synapses on the interposed nuclei.
Which deep nuclei of the cerebellum are a part of the DSCT? How do fibers leaving these nuclei leave the cerebellum and where do they go?: *interposed
*fibers leave through the SCP and cross to synapse at the contralateral red nucleus and VL region of the thalamus
What is the function of the cerebrocerebellar system?: It receives a copy of the "motor plan" from the cerebrum and is involved in motor planning and practicing complex movements.
Where is the cell body of the first order neuron of the cerebrocerebellar system? Where does this neuron travel? Where does it synapse?: *cell body is in the cerebral cortex
*travels down ipsilateral corticopontine tracts
*synapses on ipsilateral pontine nuclei
Describe the path of the second order neuron of the cerebrocerebellar system - where is its cell body, how does it travel, and where does it synapse?: *cell body is in the pontine nucleus
*decussates and passes through the contralateral MCP
*synapses on Purkinje cells in the contralateral cerebrocerebellar cortex
Which of the deep nuclei is involved in the cerebrocerebellar pathway? How do projections from this nucleus leave the cerebellum?: *the dentate nucleus
*projections leave through the SCP
Continue the path of the cerebrocerebellar tract after it leaves the cerebellum.: Fibers decussate and synapse on either the contralateral red nucleus or VL region of the thalamus. From the thalamus, fibers travel to the primary motor cortex.
Describe the basic loop (in general terms) of the cerebrocerebellar pathway.: Information travels from the cerebral cortex to the cerebellum and back to the cortex.
Describe the basic loop (in general terms) of the spinocerebellar tract.: Information from the limbs travels to the cerebellum and is then passed to the contralateral cerebral cortex.
What are the two routes taken by CN VIII fibers arising from the peripheral vestibular apparatus?: 1.Synapse at ipsilateral vestibular nucleus
2.Pass through the ICP and synapse on Purkinje cells in the FN lobe and vermis
What is the path taken by nerves arising from the vestibular nucleus that enter the cerebellum?: They pass through the ipsilateral ICP and synapse on Purkinje cells in the vermis and FN lobe.
Where do projections from the Purkinje cells of the FN lobe travel?: 1.To synapses in the ipsilateral fastigial nucleus
2.Through the ipsilateral ICP to synapses on the vestibular nucleus
What are the functions of the vestibulocerebellar pathways?: *posture
*balance
*eye movements
Where do projections from the fastigial nucleus travel?: 1.To the reticular formation
2.Through both ipsilateral and contralateral ICPs to synapse on vestibular nuclei on both sides
Where do descending fibers of the reticular formation travel?: Down the reticulospinal tract.
Where do outgoing (i.e. not to cerebellum) fibers of the vestibular nuclei travel?: *to the spine via the ventral and lateral vestibulospinal tracts
*rostrally via the MLF
What is the function of the inferior olivary nucleus?: Adaption of movement to changes in the environment.
Describe the output tracts of the inferior olivary nuclei.: Project climbing fibers through the contralateral ICP...
*to all three cerebellar cortices where they synapse on Purkinje cells in 1:1 ratio
*to direct synapses on the deep nuclei
What 3 structures send inputs to the inferior olivary nuclei?: Red nuclei, cerebral cortex, and spinal cord.
Why are lesions to the MCP associated with gait ataxia?: Because connections from the contralateral pons are lost.
What is the effect of a lesion to the SCP?: Intention tremor
What effects will be seen with a lesion to the left pontine nucleus?: Ataxia on the right (i.e. contralateral) side.
Lesions to the ICP can cause: 1.ataxia 2.nystagmus What structures are damaged to cause each of these effects?: 1.DSCT or fibers from the inferior olivary nucleus
2.Fibers to or from the vestibular nuclei
Lesions to the cerebellum or associated structures almost always produce ipsilateral effects, but there are at least 2 exceptions - what are they?: 1.Unilateral lesions to pontine nuclei
2.Unilateral lesions to inferior olivary nucleus
What is the blood supply for the ICP?: PICA
What is the blood supply for the MCP?: AICA
What is the blood supply for the SCP?: Superior cerebellar artery.

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