Basal Ganglia B&B Flashcards
what are the 5 components of the basal ganglia?
- substantia nigra
- subthalamic nucleus
- putamen
- caudate nucleus
- globus pallidus
striatum vs lentiform nucleus
striatum = putamen + caudate (divided via internal capsule, putamen inferior)
lentiform nucleus = putamen + globus palidus (medial to putamen)
what is the essential function of the basal ganglia?
modify voluntary movement for complex movements
receives input from cortex about what movement is desired, provides feedback to cortex to either stimulate (direct pathway) or inhibit (indirect pathway) motor activity
which 2 structures of the basal ganglia secrete GABA to inhibit the thalamus?
the thalamus wants to initiate movement via signals to the cortex
the pars reticulata (of substantia nigra) and globus palidus internus secrete GABA, which inhibits the thalamus - “tonic inhibition”
this is why there is no motion at rest
describe what happens in the direct pathway of the basal ganglia (4)
direct pathway = stimulate movement
- cortex secretes excitatory glutamate onto striatum (putamen + caudate)
- striatum secretes inhibitory GABA onto globus pallidus internus and pars reticulata (of substantia nigra)
- this DISinhibits the thalamus, freeing it to signal to the cortex to initiate movement [recall these structures usually secrete GABA onto the thalamus]
- at the same time, the cortex activates the pars compacta (of substantia nigra), which amplifies the action of the striatum via dopamine (D1 receptors)
describe what happens in the indirect pathway of the basal ganglia (4)
Indirect pathway = Inhibit movement
- cortex secretes excitatory glutamine onto the striatum (putamen + caudate)
- striatum secretes inhibitory GABA onto globus pallidus externus, which normally secretes GABA onto the subthalamic nucleus
- the DISinhibited subthalamic nucleus enhances the activity of the globus pallidus internus (that being secreting GABA onto the thalamus)
- at the same time, the cortex stimulates the pars compacta (of substantia nigra), which inhibits the striatum via dopamine (D2 receptors) to modulate the indirect (inhibitory) pathway
fill in the blanks regarding the DIRECT pathway of the basal ganglia:
- cortex secretes ______ onto striatum
- striatum secretes ______ onto ______ and _______
- this [activates/inhibits] the thalamus
- at the same time, the cortex activates the _______, which amplifies the action of the striatum via _____ receptors
direct pathway = stimulate movement
- cortex secretes excitatory glutamate onto striatum (putamen + caudate)
- striatum secretes inhibitory GABA onto globus pallidus internus and pars reticulata (of substantia nigra)
- this DISinhibits the thalamus, freeing it to signal to the cortex to initiate movement [recall these structures usually secrete GABA onto the thalamus]
- at the same time, the cortex activates the pars compacta (of substantia nigra), which amplifies the action of the striatum via dopamine (D1 receptors)
fill in the blanks regarding the INDIRECT pathway of the basal ganglia:
- cortex secretes ______ onto the striatum
- striatum secretes ______ onto _______, which normally secretes GABA onto the _____
- the DISinhibited ________ enhances the activity of the ________
- at the same time, the cortex stimulates the _____, which inhibits the striatum via _____ receptors to modulate the pathway
Indirect pathway = Inhibit movement
- cortex secretes excitatory glutamine onto the striatum (putamen + caudate)
- striatum secretes inhibitory GABA onto globus pallidus externus, which normally secretes GABA onto the subthalamic nucleus
- the DISinhibited subthalamic nucleus enhances the activity of the globus pallidus internus (that being secreting GABA onto the thalamus)
- at the same time, the cortex stimulates the pars compacta (of substantia nigra), which inhibits the striatum via dopamine (D2 receptors) to modulate the indirect (inhibitory) pathway
which receptors does the pars compacta of the substantia nigra act on in the direct vs indirect pathway of the basal ganglia, and why is this clinically relevant?
either way, secretes dopamine - this is relevant because the pars compacta is what gets destroyed in Parkinson’s, thus leading to decreased dopamine!
direct (movement) pathway: dopamine binds stimulating D1 receptors
Indirect (Inhibitory) pathway: dopamine binds inhibitory D2 receptors
which part of the basal ganglia degenerates in Parkinson’s?
pars compacta (of substantia nigra): secretes dopamine to modulate indirect/direct pathways
direct (movement) pathway: dopamine binds stimulating D1 receptors
Indirect (Inhibitory) pathway: dopamine binds inhibitory D2 receptors
what is the common factor among Parkinson’s, Huntington’s, hemiballism, and Wilson’s disease?
movement disorders all resulting from damage to part of the basal ganglia
which part of the basal ganglia is damaged in the following movement disorders?
a. Huntington’s
b. Parkinson’s
c. Wilson’s
d. hemiballism
a. Huntington’s - striatum (putamen + caudate)
b. Parkinson’s - substantia nigra (pars compacta + pars reticulata)
c. Wilson’s - globus pallidus (externus + internus) and/or striatum
d. hemiballism - subthalamic nucleus
which basal ganglia pathway uses dopamine to modulate motor control?
nigrostriatal pathway: dopamine signaling originates from substantia nigra pars compacta, spreads to caudate and putamen
this pathway degenerates in Parkinson’s
what is the embryonic origin of the subthalamic nucleus vs the substantia nigra?
diencephalon —> subthalamic nucleus
mesencephalon —> substantia nigra (pars compact/reticulata)
what is the cause and effect of lesions to the subthalamic nucleus?
caused by lacunar stroke, causes contralateral hemiballismus
