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ACaffeine blocks ADH, alcohol dilates the nephron
BCaffeine dilates the nephron, alcohol blocks ADH
CBoth act by blocking ADH from the pituitary
DBoth act by dilating vessels within the nephron
Answer & Solution
Correct answer: B. Caffeine dilates the nephron, alcohol blocks ADH
1. Coffee, tea and alcoholic drinks all increase urine volume, but not by the same route.
2. Caffeine promotes vasodilation in the nephron, which raises the filtration rate.
3. Alcohol inhibits ADH release from the posterior pituitary.
4. With less ADH, the collecting duct recovers less water, so more of it leaves as urine.
5. Assigning ADH inhibition to caffeine would confuse the two mechanisms.
_Source: OpenStax Anatomy and Physiology (CC BY 4.0), Ch 25 "The Urinary System", section 25.9 Regulation of Fluid Volume and Composition_
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