Neuroscience Week 4: Basal Ganglia Motor Loop Flashcards
The associative motor cortex is located in
Supplementary motor area
or
premotor area
Basal Ganglia Pathway Overview
Associative Cortex and Basal Ganglia pathway
Associative cortex to Basal Ganglia
(basal ganglia have no direct connections to LMN)
Basal ganglia through the globus paladus connects with the thalamus (basal ganglia supervise output of primary cortex and alter the excitability of the primary motor cortex through the thalamus)
The final output of the basal ganglia on the thalamus is inhibitory
so how well it works depends on if the thalamus can be regulated properly and pathology is too much (Parkinson’s) or too little inhibition (Huntington’s Disease)
Parkinson’s Gait
small steps
hunched over
turn slowly little steps
Choreiform Gait
unable to filter out unwanted movements
such as in Huntingtins Disease
Identify
Structures and methods Involved in regulating motor function of basal ganglia
- Subthalamic nucleus
and
- Substantia nigra
through dopamine
Identify
Brief description of motor loop of basal ganglia
- premotor area glutamatergic input to putamen (excitatory input)
- information flows through basal ganglia
- medial segment of globus paladus sends GABA input to thalamus and has an inhibitory role on the thalamus (inhibitory)
- Thalamus sends Glutamate signal to cerebral cortex (excitatory)
- Thalamalcortical input determines the ability to properly carry out those movements
too much thalamocortical input
too many unwanted movements
too little thalamicortical activation
cannot initiate a movement
Basal Ganglia Motor Loop
Basal Ganglia parallel processing loops
4 listed
Basal Ganglia Motor loop
regulates motor activity
Basal Ganglia Oculomotor Loop
regulation of eye movements
Basal Ganglia Prefrontal loop
problems with cognition
Basal Ganglia Limbic Loop
important in emotion and …….
Basal Ganglia Parallel Processing loops are regulated by?
Dopamine
Basal Ganglia vs Cerebellum control of movement
Question 1
C Modulating thalamic inputs to motor cortex
Motor loop pathways of the Basal Ganglia
2 listed
- Direct Pathway - Facilitates movement
- Indirect Pathway - Inhibits Movement
Motor loop pathways of the Basal Ganglia: Direct Pathway
Motor Cortex Glutamate +→x Putamen GABA -→| Globus Paladus internal segment (GPI) This is inhibited so it doesn’t happen as much (GABA -→|) Thalamus Glutamate +→x Motor cortex
So when the cortex excites putamen it is hyperactive and inhibits GPI so the thalamus is disinhibited and directs/facilitates movement
Motor loop pathways of the Basal Ganglia: Indirect Pathway
Motor Cortex Glutamate +→x Putamen GABA -→| Globus Paladus external segment GABA -→| Subthalamic Nucleus Glutamate +→x Globus Paladus internal segment (GPI) GABA -→| Thalamus
So excites the GPI and inhibits the Thalamus and inhibits movement
Putamen and Globus Palladus neuron neurotransmitter types
>90% are GABAergic projection neurons
Motor loop pathways of the Basal Ganglia: Direct & Indirect Pathway Firing Patterns
Question 2
B. Activation of the indirect pathway involves the subthalamic nucleus
dopaminergic regulation of Basal Ganglia direct pathway
- D1 Receptor makes neurons more excitable
- stimulates Direct pathway
- In parkinsons have a lack of Dopamine and as a result, have a difficulty facilitating movement
- Dopamine makes these neurons more likely to fire
dopaminergic regulation of Basal Ganglia Indirect pathway
D2 Receptor are inhibitory neuromodulators
make neurons less likely to fire and make them require more glutamate to fire
makes these neurons less likely to fire
Basal Ganglia Direct pathway Dopamine Receptor
D1 Stimulatory Neuromodulator
↑cAMP
Basal Ganglia indirect pathway Dopamine receptor
D2 Receptor inhibitory neuromodulator
↓cAMP
↑K<span>+</span> currents
↓ volatage gates Ca2+ currents
D1 and D2 receptors
Basal Ganglia Direct Pathway D1 receptors
Basal Ganglia Indirect Pathway D2 receptors
Question 3
Parkinson’s Disease degeneration of?
degeneration of Nigrostriatal DA Neurons
Loss of dopamine in Basal Ganglia Circuitry
Decreased activation of Direct pathway
Loss of dopaminergic inhibition of Indirect pathway
Cardinal signs of Parkinson’s Disease
6 listed
Resting Tremor (goes away with activity)
Ridgity with cogwheeling
Bradykinesia (Akinesia) difficulty rising (slowness of movement)
Posture instability
Shuffling gait
Micrographia
Parkinson’s TRAPS your body
Basal Ganglia side and control
- Right BG circuitry to left side of body
- Left BG circuitry to right side of body
Deep brain stimulation for Parkinsons disease
place low-frequency electrodes to stimulation Inhibition of STN (Subthalamic nucleus) or GPi
great therapeutic value and alleviates some motor symptoms
Question 4
E. all of the above
Huntington’s disease brain
almost no head of caudate/putamen
Huntington’s disease Etiology
Autosomal Dominant Disorder
Huntington’s disease Pathophysiology
no inhibitory output to the thalamus and the thalamus goes crazy and there is too much excitatory input to motor cortex
Pyramidal signs or ranking of common movement disorders
Basal ganglia signs (extrapyramidal signs)
Stroke in subthalamic nucleus on one side
hemiballismus - wild flinging of one limb or arm on the contralateral side and is most frequently unilateral
Common mixed movement disorders
question 5
basal ganglia have no direct connections to
LMNs
