Pharmacology Pharmacodynamic Mechanisms 4

Question 1

Which second messenger is produced when Gs-coupled receptors activate adenylyl cyclase?

Accepted Answer

Cyclic AMP (cAMP)

Answer

Gs stimulates adenylyl cyclase to convert ATP to cAMP, which then activates protein kinase A (PKA) to phosphorylate intracellular targets.

Question 2

Noncompetitive (insurmountable) antagonism is characterized by:

Accepted Answer

Reduction of Emax that cannot be overcome by increasing agonist dose

Answer

Noncompetitive antagonists reduce the maximum effect because they either bind irreversibly or at an allosteric site, precluding full receptor activation regardless of agonist concentration.

Question 3

Which ion channel mechanism is responsible for the pharmacodynamic action of benzodiazepines?

Accepted Answer

Enhancement of GABA-A chloride channel opening frequency

Answer

Benzodiazepines act as positive allosteric modulators at GABA-A receptors, increasing the frequency of chloride channel opening in response to GABA.

Question 4

Drug A has an EC50 of 2 mg/kg and Drug B has an EC50 of 20 mg/kg for the same endpoint. Which statement is correct?

Accepted Answer

Drug A is more potent than Drug B

Answer

A lower EC50 means a smaller dose produces 50% of the maximum effect, making Drug A more potent than Drug B.

Question 5

Receptor tyrosine kinase (RTK) signaling is most closely associated with:

Accepted Answer

Activation of intracellular kinase cascades (minutes)

Answer

RTK activation leads to receptor autophosphorylation and activation of downstream kinase cascades (e.g., MAPK/ERK, PI3K/Akt) within minutes.

Pharmacology Practice Test

Pharmacology Practice Test

Pharmacology Pharmacodynamic Mechanisms 4