Question 1: Define homeostasis and explain its importance in maintaining water balance in the body.

Answer: Homeostasis is the process by which the body maintains a stable internal environment, including water balance, by regulating various physiological processes to keep conditions within narrow limits.

Question 2: Describe the role of the kidneys in regulating the body's water content.

Answer: The kidneys filter blood to remove excess water and waste, adjusting urine concentration to maintain water balance according to the body's needs.

Question 3: What is the function of the nephrons within the kidneys?

Answer: Nephrons are the functional units of the kidney that filter blood, reabsorb essential substances, and produce urine.

Question 1: If a person consumes 2 liters of water daily and excretes 1.8 liters in urine, what percentage of water intake is excreted as urine? Show your calculation.

Answer: Percentage excreted = (Urine volume / Water intake) x 100 = (1.8 / 2) x 100 = 90%

Question 2: A person's urine output is 1.2 liters in 24 hours. If their kidneys reabsorb 95% of the water filtered, what is the total volume of water filtered by the kidneys in that period? (Assume all reabsorbed water is from the filtered volume).

Answer: Total filtered volume = Urine output / (1 - Reabsorption fraction) = 1.2 / (1 - 0.95) = 1.2 / 0.05 = 24 liters

Question 1: Describe a simple experiment to investigate the effect of water intake on urine concentration. Include the variables involved and safety precautions.

Answer: Students can measure their urine volume and concentration after varying water intake levels over a specified period. Independent variable: amount of water consumed; dependent variable: urine concentration; control variables: activity level, diet. Safety precautions include handling urine samples hygienically, wearing gloves, and ensuring proper disposal.

Question 2: Identify two factors that could affect the accuracy of results in kidney function experiments and suggest ways to minimize their impact.

Answer: Factors include variations in activity levels and diet; to minimize impact, standardize activity and diet before the experiment and perform multiple trials for accuracy.

Question 1: A person drinking 1 liter of water produces urine with a specific gravity of 1.005, while another person drinking 3 liters produces urine with a specific gravity of 1.020. What does this suggest about their water reabsorption, and why?

Answer: Lower specific gravity in the first person indicates less water reabsorbed, meaning their kidneys produce more dilute urine due to higher water intake. The second person’s higher specific gravity suggests more water reabsorbed, producing more concentrated urine.

Question 1: Explain how the kidneys help maintain water balance in the body during dehydration and overhydration. Include the roles of ADH and the collecting ducts. (6 marks)

Answer: During dehydration, the body releases more ADH (antidiuretic hormone), which makes the collecting ducts more permeable to water, allowing more water to be reabsorbed and producing concentrated urine. During overhydration, less ADH is released, reducing water reabsorption, leading to dilute urine, helping restore water balance.

Question 1: Describe how knowledge of kidney function is used in the development of treatments for conditions like diabetes insipidus.

Answer: Understanding how ADH regulates water reabsorption helps in developing hormone replacement therapies or medications that mimic ADH to treat conditions like diabetes insipidus, where the kidneys cannot conserve water properly.