Exam 3: The Cerebellum Flashcards
zVermis function
proximal and trunk muscle control (medial anterolateral corticospinal tract)
Flocculonodular function
vestibuloocular control
Intermediate part function
control of distal muscles in the arms and legs
Lateral Part Function
planning and motor program for the extremities (limbs)
Where do mossy fibers come from?
Mossy fibers come from all of the regions of the cortex, brainstem and spinal cord
Where do climbing fibers come from?
Climbing fibers are exclusively from the olivary nucleus
Corticopontocerebellar Pathway function
1) Cortical Inputs from all major cortical lobes, which provides major sensory information to the cerebellum (also referred to as corticocerebellar)
2) Corticopontocerebellar Pathway
a. Corticopontine fibers travel to the ipsilateral pons and synapse in the pontine nuclei (in pons)
b. From there pontocerebellar fibers then cross the midline to enter the contralateral middle cerebellar peduncle and give rise to mossy fibers that reach the cerebellar cortex
Cortico-olivocerebellar Pathway function
Function is to coordinate fine motor movements
1) The cortico-olivary fibers arise from nerve cells cortex and descend through the corona radiata and internal capsule to terminate bilaterally on the inferior olivary nuclei.
2) The inferior olivary nuclei give rise to fibers that cross the midline and enter the opposite cerebellar hemisphere through the inferior cerebellar peduncle
3) These fibers terminate as the climbing fibers in the cerebellar cortex.
Spinocerebellum Pathway Function
This pathway regulates body and limb movements
1) It receivesproprioceptioninput from the dorsal columns of thespinal cord and thetrigeminal nerve, as well as from visual andauditorysystems.
2) It sends fibers to deep cerebellar nuclei, which in turn project to both the cerebral cortex and the brain stem, thus providing modulation of descending motor systems.
Vestibulocerebellum Pathway
Via this pathway the cerebellum receives input from the semicircular canals in ear and from the vestibular nuclei in brainstem vestibular nuclei, as well as visual input. Lesions cause disturbances of balance and gait.
Molecular Layer
– contains interneurons, the dendrites of the 2nd cell layer and axons of the 3rd cell layer (below)
Purkinje Cell Layer
large, flask shaped cells
Granule Layer
tiny cells that are densely packed into the cerebellum. The number cells in the layer can actually equal the total number of cells in the entire nervous system
Synaptic Inputs Mossy
1) Mossy fibers – these axons originate in various parts of the nervous system but travel into the cerebellum together and provide excitatory input to the granule cells.
2) The axons of the cerebellar granule cells then go into the molecular layer and form the parallel fibers
3) The parallel fibers in turn make excitatory contacts with the purkinje
4) These purkinje cells synapse onto the deep cerebellar nuclei, inhibiting them, which then provide the output of the cerebellum.
Synaptic Inputs Climbing
1) Climbing fibers– these axons come from the olivary nucleus in the medulla of the brainstem. The function is exclusively coordination fine motor movements
2) The fibers come into the cerebellum and form strong excitatory synapses with the purkinje neurons–recall they are the key neurons that synapse with deep nuclei
3) Thus, the purkinje neurons receive both climbing fiber input (direct) and mossy fiber input (indirect)
