Basal Ganglia Flashcards
What structures make up the basal ganglia?
- Caudate nucleus
- Putamen
- Globus pallidus (internus and externus)
- Subthalamic nucleus
- Substantia nigra
Caudate + Putamen = Striatum
Putamen + GP = Lentiform
What structures make up the Lentiform nucleus?
- Putamen
- Globus Pallidus (internus + externus)
What structures make up the striatum?
Putamen (motor) + Caudate (cognitive)
What neurons are excitatory and what are inhibitory in the basal ganglia?
- Glutamate: Excitatory
- GABA: Inhibitory
What pathway initiates movement?
Direct pathway (disinhibiting thalamic control of motor planning)
What pathway terminates movement?
Indirect
What does the substantia nigra do?
Inhibits the thalamus (inhibiting movement)
How does dopamine affect the direct pathway?
D1 receptors
- Excites neurons
- Increases movement
How does dopamine affect the indirect pathway?
D2 receptors
- Inhibits the neurons
- Decreases activity of indirect pathway
- Decreases termination of movement
- Initiates movement
What structure in the BG inhibits the thalamus and thus inhibits movement?
Substantia Nigra
What structure inhibits the substantia nigra? (meaning it does not inhibit the thalamus = More MOVEMENT) (direct pathway)
Striatum
What structure excites the substantia nigra? (meaning the SN inhibits the thalamus to a greater degree = LESS movement) (Indirect pathway)
Subthalamic nucleus
What is the subthalamic nucleus influenced by? (indirect pathway)
Inhibited by the Globus Pallidus Externis which is in turn inhibited by the Striatum
- Overall the Subthalamic nucleus EXCITES the Substantia nigra
How is the substantia nigra influenced in the direct pathway?
- Is the SN inhibited or stimulated?
- What structure does this stimulating/inhibiting?
Inhibited by the striatum therefore it cannot inhibit the thalamus =>
- Thalamus is more powerful and abke toi initiate movement
In what pathway is the substantia nigra inhibited?
Direct (this will mean it cannot inhibit the thalamus so the thalamus is excited = More Movement)
In what pathway is the substantia nigra excited?
Indirect
- This will inhibit the thalamus thus inhibiting movement
What is the effect of dopamine on movement?
Increases movement
What inhibits the substantia nigra (direct pathway)?
Striatum
What stimulates the substantia nigra (indirect pathway)?
Subthalamic nucleus
What is the subthalamic nucleus inhibited by? (indirect pathway)
Globus pallidus externus (inhibted by striatum, so overall it is stimulated to stimulate the substantia nigra)
What structures are invloved in the indirect pathway but not the direct?
- Globus pallidus externa
- Subthalamic nucleus
What does the striatum release?
GABA (inhibits)
- both GPi/SN (direct) and GPe (indirect)
Outside of the motor cortex which stimulates the striatum (caudate nucleus + Putamen) what other basal ganglia structure releases glutamte (stimulates)?
Subthalamic nucleus (stimulates SN)
