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G-Protein Coupled Receptors and Their Role in Synaptic Transmission

Explore the complex world of indirect mechanisms in synaptic transmission, pivotal for understanding neural communication. This assessment covers key concepts, enhancing comprehension and application in neuroscience, relevant for...

Questions: 29 | Attempts: 10 | Last updated: Nov 13, 2025

Sample Question 1
What are the two mechanisms by which G-proteins affect cell activity?

1. Through G-protein coupled receptors; when the G-protein is activated by it's receptor the alpha and beta/gamma subunits dissociate. The free subunits modulate the activity of the intracellular targets. When Ach binds to its muscarinic receptor on cells in the atrium of the heart, a G-protein is activated. The free beta/gamma subunit binds to ion channels, thereby slowing heart rate.2. Activation of enzymes can also produce intracellular second messengers. Activation of G-Protein in cardiac muscle cells--> binding of NE to beta-adrenergic receptors --->alpha and beta/gamma subunits--->stimulate the enzyme adenylyl cyclase--> increased cAMP---> cAMP-dependent protein kinase---> phosphorylation. (may result in long lasting effects, and cascade of events)

Activation of G-Protein in liver cells leads to the release of digestive enzymes.

Activation of G-Protein in cardiac muscle cells leads to the activation of apoptosis.

Activation of G-Protein in nerve cells leads to direct muscle contraction and relaxation.

Sample Question 2
What are direct targets for transmitter activation?

GABA receptors

Potassium and Calcium channels.

Sodium channels

Chloride channels

Sample Question 3
What effect does opening of potassium (via indirectly acting transmitters) channels have on N-type calcium channels?

The inhibit the calcium channels in the sympathetic neurons and increase the probability that calcium channels open in response to depolarization in cardiac muscle cells.

B. They decrease the probability of calcium channels opening in both sympathetic neurons and cardiac muscle cells.

A. They have no effect on N-type calcium channels.

C. They only affect calcium channels in cardiac muscle cells but not in sympathetic neurons.

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