Which axis on the Drug Response Curve represents the magnitude of the response?

• A. X-axis
• B. Y-axis
• C. Both axes
• D. None

Answer: (B)

The main idea is that a dose–response curve separates what you control from what you measure. The horizontal axis shows the dose or concentration you apply, while the vertical axis shows the size of the effect—the magnitude of the response. This magnitude is the dependent variable and is typically expressed as a percent of maximal effect or another response unit, so it’s plotted on the vertical axis. As dose increases, the response grows in magnitude up to a maximum, which is why the curve rises on the vertical scale. The other options don’t fit because the x-axis is about how much drug is given, not how large the response is; saying both axes or none would misplace the measure of effect.