Neuro: Basal Ganglia Flashcards
The direct pathway of the basal ganglia leads to cortex ___________
excitation
The GPi is (inhibited or activated) in the direct pathway
INHIBITED (allowing the thalamus to be disinhibited)
What makes up the striatum?
- caudate
- nucleus accumbens
- putamen
What makes up the lenticular nucleus?
putamen and the globus pallidus
True or false: the basal ganglia has no major outputs to LMNs?
TRUE
it can only influence LMNs via the cerebral cortex
Input to striatum from cortex is _____________ and glutamate is the NT
excitatory
How does the basal ganglia mediate its output?
globus pallidus internal
substantia nigra reticulum
True or False: BG output is inhibitory
TRUE (mediated via GABA)
What is the main role of the BG?
to send the thalamus excitatory and inhibitory messages via the striatum
What are 4 loops of the BG?
1) Motor (learned movements)
2) Cognitive (intention)
3) Limbic (emotion)
4) Oculomotor (fast eye movements)
Walk thru the circuit of the direct pathway
SNc releases D1 –> excites the striatum which inhibits the GPi which can no longer inhibit the VA/VL of the thalamus so the Premotor cortex gets ACTIVATED
In the indirect pathway, thalamic activity is ____________
decreased
What is the circuit of the indirect pathway?
D2 inhibits striatum so inhibition of GPi is released allowing GPi to inhibit the thalamus
Why is thalamic activity DECREASED in the indirect pathway?
because the striatum cannot inhibit GPi
What is the purpose of the subthalamic nucleus?
part of the hyperdirect pathway
output is excitatory to GPi and SNr
inhibits unwanted movements
The GPi receives ____________ input from the striatum and the GPe but ______________ input from the subthalamic nucleus
inhibitory (striatum and GPe)
excitatory (subthalamic nucleus)
Hypokinesia is associated with _____________
Parkinsons
Define bradykinetic syndrome
increased inhibitory output of GPm to VL thalamic motor nuclei
What is a hyperkinetic syndrome?
decreased inhibitory output of GPm to VL thalamic motor nuclei –> enhanced motor stimulation
Why can a lesion to the subthalamic nuclei cause hemiballismus?
because it lessens the stimulation of GPm (which inhibits the thalamus)
Huntington’s Disease loses the __________ pathway
indirect (losing the inhibitory effect on the thalamus –> over excited)
What are 3 etiologies of basal ganglia disorders?
1) infarct, hemorrhage, tumor in striatum or STN
2) Degenerative disorders (Parkinson’s, Huntington’s)
3) medication side effects
Name 4 movement disorders that are unrelated to basal ganglia problems
1) essential tremor
2) myoclonus/asterixis
3) dystonia
4) tic
