A healthy person does not drink for eight hours overnight. Urine is collected during the first two hours and the final two hours. The mean ADH concentration in the blood is measured during each period.
| period | mean ADH concentration / pg cm−3\mathrm{pg\,cm^{-3}}pgcm−3 | urine volume / cm3\mathrm{cm^3}cm3 |
|---|---|---|
| first two hours | 1.6 | 140 |
| final two hours | 4.8 | 55 |
Explain the difference in urine volume shown in the table and predict how the concentration of the urine in the final two hours compares with that in the first two hours.
94 exam-style questions on Edexcel GCSE Biology 7.4 Blood glucose and the urinary system, covering 7.4.1 Insulin and blood glucose control, 7.4.2 Glucagon and blood glucose regulation, 7.4.3 Type 1 and type 2 diabetes, 7.4.4 Structure of the urinary system, 7.4.5 Structure and function of the nephron, 7.4.6 ADH and water regulation, 7.4.7 Treatments for kidney failure, and 7.4.8 Production of urea in the liver. Each one has a worked solution and a mark scheme showing where the marks go.