Basal Ganglia

vaheeda1's version from 2017-12-12 00:44

Intro to BG

Question Answer
What is the most simple description of the motor circuit of the basal ganglia?cortex > putamen > cortex > CST and CBT
What three structures comprise the lenticular nuclei (“candy corn”)?putamen, GPi, and GPe
What three stucutures comprise the striatum?caudate, nucleus accumbens, putamen
Which part of the BG is in the diencephalon?subthalamus
Which parts of the BG are in the midbrain?substantia nigra (compact and reticular)
What are the inputs to the BG?caudate and putamen
What are the outputs of the BG?GPi and SNr
What is the GPe most related to?subthalamus
Which part of the nigra is repsonsible for DA synthesis?substantia nigra compacta
Describe the morphology of the caudate?C-shaped; on lateral edge of entire lateral ventricle
What are the caudate and putamen separated by?internal capsule
What type of neurons are in the output of the striatum? What disease are they wiped out by?medium spiny neurons; Huntingtons
D1 receptors are ____ by dopamine and involved in the ____ pathway. D2 recpetors are ____ by dopamine and involved in the ____ pathway. Both are ____-ergic.excited/direct; inhibited/indirect; GABA-ergic
What does the GPe do? What types of neuronsregulates the GPi; GABA-ergic
What is the main difference between the GPi and SNr? What types of neurons?SNr is BG output for eyes; GABA
What tract takes neurons from the GPi to the thalamus?lenticular fasciculus
What does the subthalamus do? What types of neurons?it modifies info between the thalamus and substantia nigra.; glutamate
What is the only part of the BG that has excitatory neurons? What other excitatory neurons are involved?subthalamus – glutamate; neurons firing on BG from cortex. Neurons leaving thalamus back to cortex.
What type of neurons does the GPi have?GABA
What type of cells are lost in Parkinsons?SNc
What is the link between BG and motor neurons?PPN (pedunculopotine nuclei)
The feedback loop between the subthalamus and ____ is critical for normal function of the BG.GPe

Wiring (Do drawings before reviewing!)

Question Answer
Inputs to the putamen?cortex and thalamus
Outputs from the putamen?D1: GPi, SNr, SNc; D2: GPe
Inputs to GPi?D1 from putamen; glutamat-ergic from subthalamus
Inputs to GPe?D2 from putamen; glutamergic from subthalamus
Outputs from GPi?thalamus and PPN
Outputs from SNr?thalamus, PPN, SC
Outputs from GPe?subthalamus, putamne, GPi, SNr
Inputs to subthalamus?cortex
Outputs from subthalamus?GPi, SNr, GPe
Inputs to the compacta?D1s from putamen, cortex
Outputs of the compacta?to striatum (dopaminergic)

Circuits basics

Question Answer
Cortex acitivity up > ____ activity is up > GPi is up and sends ____ to the thalamus > ____ thalamus activity > ____ motor cortex activitycortex is excitatory > STN activity ↑ > PGI is ↑ and is inhibitory to thalamus > less motor cortex activity
The direct and indirect pathways are opposing in that adjust the magintude of the ____ .GPi inhibitory action on the cortex
The direct pathway ____ the thalamus and thus ____ the cortex. The indirect pathway ____ the thalamus and thus ____ the cortex.disinhibits, disinhibits; inhibits, disfaciliatates
Note there are also ACh neurons in putamen. These are “____”
DA neurons are “____” neurons.“go”

Direct Pathway

Question Answer
1. Cortex fires ____ on D1 cells in ____.glutamate; putamen
2. D1 cells fire ____ on ____/____.GABA; GPi/SNr
3. GPi/SNr fire ____ on ____. Process?GABA on thalamocortical neuron; disinhibition
4. thalamocortical neuron fires ____ on cortex > ____ in descending pathway activity.glutamate > increaes
In the DA modfication, what does SNc fire onto?d1 cells of putamen
What does DA cause?slight increase in the direct pathway

Indirect Pathway

Question Answer
1. Cortex fires ____ on D2 cells in ____.glutamate; putamen
2. D2 cells fire ____ on ____.GABA; GPe
3. GPe cells fire ____ on ____.GABA on STN
4. STN fires ____ on ____.glutamate on GPi/SNr
5. Therefore the thalamas and cortex are ____.disfaciliated
How does the DA pathway differ in the indirect?DA is fired upon D2 cells, which are inhibited > instead of greater disfaciliating outcoming, you get an increase in CST activity