These eight original questions follow the four lessons in homeostasis and the urinary system. The students and figures are invented.
Try each question before opening the answer, and write full sentences for the explain questions.
Questions
Q1. Name the four steps of a negative feedback loop.
Answer
Change from the normal level, detection, response by an effector, and return towards normal.
Q2. Blood water content falls. Which hormone is released in greater amount, and what does it do?
Answer
ADH is released in greater amount. It makes the distal tubule and collecting duct more permeable to water, so more water is reabsorbed.
Q3. Explain why protein does not appear in the filtrate.
Answer
Protein molecules are too large to pass through the filter between the glomerulus and Bowman’s capsule, so they stay in the blood.
Q4. Glucose is filtered but not found in normal urine. Explain.
Answer
Glucose is small, so it is filtered. All of it is then reabsorbed in the proximal convoluted tubule, so none remains to leave in urine.
Q5. A student writes: “Glucose is not filtered because the body needs it.” Correct the mistake.
Answer
Filtration depends on size and pressure, not on need. Glucose is filtered, and the need is met by reabsorption afterwards.
Q6. Invented data: on Day A a student drinks 2.0 litres and passes 1.8 litres of pale urine. On Day B they drink 0.8 litres and pass 0.6 litres of dark urine. Explain the difference.
Answer
Urine volume fell from 1.8 to 0.6 litres, and the colour changed from pale to dark. On Day B less water was drunk, so the blood became more concentrated. More ADH was released and more water was reabsorbed, so the urine was smaller in volume and darker.
Q7. Compare the ADH response to a fall in blood water with the response to a rise.
Answer
Both follow negative feedback with detection by the hypothalamus. When blood water falls, more ADH is released and more water reabsorbed, whereas when it rises, less ADH is released and less water reabsorbed.
Q8. A classmate asks you how much water a real person should drink each day. What should you say for your exam, and what should you say to your classmate?
Answer
For the exam, explain how the body adjusts water balance through ADH and the kidneys. For a real person’s needs, suggest your classmate asks a doctor or another health professional, because the answer depends on the person.
If you got these wrong
Q1 and Q2 point to explaining negative feedback. Q3 to Q5 need tracing filtration, reabsorption and urine formation.
Q6 links to interpreting water-balance data. Q7 and Q8 belong to comparing regulatory responses.
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