Basal Ganglia Flashcards
What is the basal ganglia?
Collection of subcortical nuclei that are involved in control of movement
What five nuclei are part of the basal ganglia?
The caudate, putamen, globus pallidus, subthalamic nucleus and substansia nigra
Why is the amygdala not usually counted as basal ganglia?
It is functionally part of limbic system
Which nuclei in basal ganglia receive most input?
The putamen and caudate nucleus
Which nuclei make up the striatum?
The putamen and caudate nuclei- similar anatomically and have similar functional role
What project to the striatum?
All cortical areas involved in planning and execution of movements
Where does the striatum primarily project to?
Globus pallidus and substansia nigra
Which nuclei are referred to as lenticular nucleus?
Globus pallidus and putamen
What is the globus pallidus divided into?
The internal and external segments
What sends the main projection out of basal ganglia to thalamus?
The globus pallidus internal segment and the substansia nigra pars reticulata
How does striatal information reach globus pallidus internal segment?
Two main pathways: direct and indirect pathways
What is the ansa lenticularis?
conveys information from GPi to the motor thalamus (VLN)- loops under posterior limb of internal capsule
How does information from more caudal part of globus pallidus reach VA/VL nuclei of thalamus?
The lenticular fasciculus- travel through the posterior limb of internal capsule
How many loops are there?
4- motor, cognitive, limbic and occulomotor
What is the consequence of the direct pathway?
It increases the excitatory drive from thalamus to cortex
What neurotransmitter do the cortical projections to striatum use?
Glutamate
What neurotransmitter do the striatal cells projecting to GPi use?
GABA
What neurotransmitter do the neurons projecting from GPi to thalamus use?
GABA
What is the result of the direct pathway?
The cortical signals excite striatal neurons via glutamate- the results in inhibition of GPi via striatum which uses GABA- more inhibition of GPi means less inhibition of thalamus which increases motor activity
Where do striatal neurons project to in the indirect pathway?
GPe
What additional nucleus is involved in the indirect pathway?
Subthalamic Nucleus
What is the route of the indirect pathway?
cortex (glutamate)- striatum (GABA)- GPe (GABA)- subthalamic nucleus (glutamate)- GPi (GABA)- VA/VL in thalamus (glutamate)- motor cortex
What is the consequence of the indirect pathway?
Decrease excitatory drive from thalamus to cortex
What is function of nigrostriatal axon terminals?
Release dopamine into striatum
What is the effect of dopaminergic nigrostriatal projects?
Increase motor activity- has excitatory effect on cells in striatum involved in direct pathway- has inhibitory effect on striatal cells of indirect pathway
What are local circuit neurons?
population of cholinergic neurons that do not leave striatum
What are the actions of cholinergic neruons in striatum?
Inhibit striatal cells of direct pathway and excite striatal cells of indirect pathway- decreases motor activity
What occurs as result of damage to basal ganglia?
Hyperkinesia (increased movement) or hypokinesia (decreased movement)
What are Lewy bodies?
Accumulation of protein in degenerating nigral dopaminergic cells
Name one hyperkenesic and one hypokinesic disorder.
Parkinson’s (hypo) and Huntingtons (Hyper)
