APP Module (GTown) - Basal Ganglia Pathophysiology (Hrs 1 and 2) Flashcards
What is the generalized function of the basal ganglia?
the selection of action, or turning thoughts/ideas/motivations into action
What are the key pathologies of the basal ganglia?
1) Parkinson’s Disease
2) Huntington Disease
3) Tourette’s
4) dementia pugilistica
5) OCD
What is the main motor circuit called which includes the basal ganglia?
cortico-basal ganglia-thalamocortical circuit
What are the two brain areas of the dorsal striatum?
caudate and putamen
What separates the caudate and putamen?
internal capsule
What are the majority of neurons in the basal ganglia?
medium spiny neurons (MSNs)
What are the two motor pathways in the basal ganglia?
The direct and indirect pathways
What type of input does the basal ganglia get from the cortex?
mostly excitatory glutamatergic input
What type of input does the basal ganglia get from the substantia nigra?
both excitatory and inhibitory dopaminergic input
What is the role of the subthalamic nucleus?
suppression of unwanted movements
How do you differentiate between the two types of dopaminergic neurons which originate from the substantia nigra pars compacta and synapse on the dorsal striatum?
D1-like neurons will project to the substantia nigra pars reticulata. D2-like neurons will project to the globus pallidus externa.
What are the two neural components of the basal ganglia?
1) Principal, projecting neurons (~95%)
2) Aspiny interneurons (1-2%)
What neurotransmitters do the interneurons use?
GABA and acetylcholine
What do the interneurons in the basal ganglia do?
Modulate MSNs
What electrophysiological properties do the MSNs have?
bimodal nature: up and down states
What is the purpose of the MSNs?
to convey information out of the basal ganglia
What are the three main inputs onto the average MSN?
1) cortical glutamatergic input
2) interneuronal ACh input
3) substantia nigra DA input
What are the four cortical-basal ganglia loops?
1) motor
2) oculomotor
3) prefrontal
4) limbic
What are the main inputs into the striatum?
Dorsal striatum
What NT do neurons in the globus pallidus use?
GABA
Where do the majority of neurons from the GP synapse on?
Thalamus
How long does it take for a signal to cross a synapse?
2 ms
How do we know there is an indirect GABA influence on the basal ganglia?
There is a 20-30 ms lag between stimulation of the cortex and a spike in the basal ganglia.
Where do the majority of neurons from the STN project to?
GP
What NT does the STN use?
glutamate
Why is the STN unique in the BG?
It is the only brain region to use glutamate
What are the two subdivisions of the substantia nigra?
pars compacta and pars reticulata