Motor- Specifically STOP/GO pathway

Question 1

Where is dopamine produced? Where is dopamine released?

Answer 1

• Dopamine is produced in the Substantia Nigra, pars compacta
• Dopamine is then released to the Caudate

Question 2

Are D1 receptors excitatory or inhibitory? Which pathway are they a part of?

Answer 2

• D1 receptors are excitatory
• D1 receptors are a part of the GO/DIRECT pathway

Question 3

Are D2 neurons excitatory or inhibitory? Which pathway are they a part of?

Answer 3

• D2 neurons are inhibitory
• D2 neuronsare part of the STOP/INDIRECT pathway

Question 4

What does dopamine do to the GO and STOP pathways?

Answer 4

• Dopamine turns on the GO pathway, leading to reward seeking
• Dopamine turns off the STOP pathway, which leads to reward-seeking

Question 5

What parts of the brain are involved in the direct/go pathway in order of neurotransmission?

Answer 5

• Substantia Nigra
• Caudate
• GPi
• Thalamus
• Cerebral Cortex
• Back to the caudate

Question 6

What do the Globus Pallidus internal and external produce/release?

Answer 6

• GABA

Question 7

What produces glutamate?

Answer 7

• Thalamus
• Cerebral cortex
• Subthalamic nucleus (indirect/stop pathway)

Question 8

Explain the steps of the GO pathway in the presence of dopamine

Answer 8

• Dopamine is made in the SNc and released in the caudate
• Because D1 receptors are excitatory, when dopamine is released into the caudate, GABA is fired (from the Caudate to the GPi)
• Once GABA is fired onto the GPi, GPi GABA neurons are inhibited. No GABA is released from the GPi to the thalamus.
• Because no GABA is released into the thalamus, the glutamate neurons found there are able to fire
• Glutamate is fired from the thalamus to the cerebral cortex
• Glutamate is fired from the Cerebral cortex to the caudate

Question 9

Which parts of the brain (in order of neurotransmission) are involved in the STOP pathway?

Answer 9

• SNc
• Caudate
• GPe
• Subthalamic nucleus
• GPi
• Thalamus
• Cerebral cortex
• Caudate

Question 10

Describe the steps of the STOP pathway in the presence of dopamine

Answer 10

• Dopamine is fired from the SNc to the caudate’s D2 receptors (which are inhibitory)
• This inhibition makes it so GABA cannot fire from the caudate to the GPe
• So, the GABA neurons in the GPe are not inhibited and can fire GABA to the Subthalamic nucleus
• So, the glutamate neurons in the subthalamic nucleus do not fire
• This makes it so the GPi GABA neurons do not fire either
• The rest of the process follows the same pattern as the GO pathway

Question 11

Explain the process of the GO pathway when dopamine is not present

Answer 11

• No dopamine is fired from the SNc to the caudate
• So, the D1 GABA neurons are not activated, and the GPi is not inhibited by GABA
• So, the GPi released GABA onto the thalamus
• This inhibits the thalamus’ glutamate neurons, and no glutamate is fired to the cerebral cortex
• So, the cerbral cortex’s glutamate neurons are not excited, and do not send a signal back to the caudate
• So, no movement occurs

Question 12

Explain the steps of the STOP pathway when there is no dopamine present

Answer 12

• When no dopamine is released from the SNc to the caudate, there is no dopamine on the D2 inhibitory receptors, so the caudate fires GABA
• When GABA is fired from the caudate onto the GPe, the GPe is inhibited and does not send GABA to the subthalamic nucleus
• So, the Glutamate neurons on the subthalamic nucleus are not inhibited, and instead action potentials can occur
• These action potentials lead to the release of the GABA in the GPi
• Continues on the same as the Go pathway