motor systems Flashcards
corpus striatum
caudate and putamen
input zone of basal ganglia
output structure of basal ganglia
GPi
how are connections between basal ganglia and cortex organised
in loops
there are 7 different loops
e.g. skeletal-motor loop, from SMA to basal ganglia back to SMA
general rule of loops
input from cortex –> striatum –> GPi –> thalamus –> back to original cortical structure
basal ganglia: direct pathway
Globus pallid us very active so when no movement it is actively inhibiting the thalamus –> very little activation motor cortex
activation of the cortex will activate the putamen. This will activate putamen spiny neurons which release GABA onto GPi which is surpassed. This released thalamus from inhibition which will re stimulate it
basal ganglia: indirect pathway
putamen releases GABA to GPe , suppressing its output and freeing up the sub thalamic nucleus
STN normally drives GPi via excitatory glutamergic activation, leading to thalamus suppression
basal ganglia - what is substantia nigra doing
receives input from prefrontal association cortices related to reward
makes dopaminergic connections to putamen and these project to all kinds of spiny neurons
dopamine receptors of basal ganglia
D1 - stimulating, expressed by direct pathway
D2 - inhibiting, expressed by indirect pathway
what is direct pathway
a stimulating pathway
GO signal to supplementary motor area
what is indirect pathway
response suppressing pathway
malfunction of direct pathway results in
parkinson’s disease
malfunction of indirect pathway results in
Huntington’s disease
parkinson’s - consequences of dopamine loss
little input to striatum
little activation of direct pathway
activation of indirect pathway
GPe inhibited - activates STN - drives GPi activity
GPi shuts of thalamus - reduced cortical activity - slow movements
inputs to cerebellum
spinocerebellar (proprioception)
vestibulocerebellar (body tilting)
cortocopontocerebellar (from cerebral cortex)
output cells cerebellar cortex
purkinje cells
