Basal Ganglia Flashcards
What is the general function of the cerebral cortex?
Performs “higher functions” and it also has control over motor systems
What is the general function of the basal ganglia?
Basal ganglia allows movement to happen
while also prevents any unwanted movement
What is the general function of the cerebellum?
Cerebellum monitors movements and makes
sure that movement is as what you want it to do
What are the parts of the striatum?
Putamen
Caudate Nucleus
Nucleus Accumbens - where the caudate and putamen meet
What are the parts of the globus pallidus?
Internal Segment (GPi) External Segment (GPe)
Why does cortex not communicate directly with the thalamus?
Going through the striatum and globus pallidus allow for more precise control nd communication via excitation and inhibition
Where does the GPi communicate to?
Thalamus
Where does the GPe communicate to?
Subthalamic Nucleus. Which projects to the GPi
Does the basal ganglia have any inputs to the LMNs?
No. But the BG controls the LMN via the cerebral cortex
What NT does the cortex use to give the striatum input? What type of input is it?
Glutamate.
Excitatory Input.
What NT is generally excitatory and which is inhibitory?
Excite - Glutamate
Inhibit - GABA
What is the output from the BG done through? Where does it go and what NT does it use?
The output is to the thalamus via the GPi and SNr (substantia nigra reticular part).
GABA
Describe the inputs on the striatum in the direct pathway.
Association Cortex activates the Striatum with Glutamate.
The Substantia Nigra Compact Part releases Dopamine which activates the Striatum on the D1 receptors, but inhibits it on the D2 receptors.
Describe the direct pathway.
Association Cortex activates -> Striatum inhibits -> Globus Pallidus Internal inhibits -> VA/VL Complex of Thalamus activates -> Premotor Cortex
How is the motor cortex inhibited through the direct pathway?
If the inhibition of the striatum on the GPi is minimal, the GPi will have high inhibition activity on the VA/VL complex of the thalamus. This will decrease the activity of the thalamus and inhibit the premotor cortex.
How is the motor cortex activated through the direct pathway?
If the activity of the striatum is maximal, meaning it is highly active via the association cortex and the SNc, it will inhibit the GPi heavily. This means, GPi’s inhibition of the VA/VL complex is minimal and the thalamus is active, activating the premotor cortex as a result.
Describe the inputs on the striatum in the indirect pathway.
Association Cortex activates the Striatum with Glutamate.
The SNc releases Dopamine, which has an excitatory effect on D1 receptors and an inhibitory effect on D2 receptors on the striatum.
Describe the indirect pathway.
Association Cortex activates -> Striatum (SNc sends dopamine to activate/inhibit on D1/D2 receptors) inhibits -> Globus Pallidus External inhibits -> Subthalamic Nucleus activates -> Globus Pallidus Internal inhibits -> VA/VL Complex of Thalamus activates -> Premotor Cortex
How is the motor cortex inhibited through the indirect pathway?
The D2 receptors are activated and dopamine from the SNc inhibits the activity of the striatum. This inhibition allows for increased GPi activity which inhibits the VA/VL of the thalamus and inhibits the premotor cortex, preventing any unwanted movements while voluntary movement occurs.
How is the motor cortex activated through the indirect pathway?
The D2 The D2 receptors are activated and dopamine from the SNc inhibits the activity of the striatum. This increases the GPe activity and the sub thalamic nucleus is inhibited and the activity of the GPi decreases. The VA/VL of the thalamus is disinhibited and the motor cortex can then be activated.
What changes in the direct and indirect pathway occur as a result of Parkinson’s Disease?
The dopamine D1 and D2 receptors are degenerated which leads to diminished inhibition of the GPi from the direct pathway and an increased inhibition of the GPe.
This leads to more active sub thalamic nucleus which activates the GPi which then inhibits the VA/VL of the thalamus and inhibits movement, causing the loss of movement observed in Parkinson’s.
What changes in the direct and indirect pathway occur as a result of Huntington’s Disease?
The inhibition of the GPe by the striatum is diminished which results in the GPe being very active and it inhibits both the GPi and the STN, preventing any inhibition of the VA/VL of the thalamus, leading to increased movements, often involuntary, involved in Huntington’s.
What is the general effect of the direct pathway WITHOUT dopamine?
Increases motor activity
What is the general effect of the indirect pathway WITHOUT dopamine?
Decreases motor activity
What is the general effect of the direct pathway WITH dopamine?
Dopamine will excite the direct pathway increasing the motor activity further
What is the general effect of the indirect pathway WITH dopamine?
Dopamine will inhibit the indirect pathway, which increases motor activity
