Question 1: Define osmoregulation and explain its importance in maintaining water balance in humans.

Answer: Osmoregulation is the process by which the body controls the concentration of water and solutes in the blood to maintain homeostasis. It is important to prevent dehydration or overhydration, ensuring cells function properly.

Question 2: Describe the main function of the kidneys in water regulation.

Answer: The kidneys filter blood to remove excess water and waste products, adjusting the concentration of urine to maintain water balance and blood pressure.

Question 3: Explain how ADH (antidiuretic hormone) influences urine concentration.

Answer: ADH increases the permeability of the kidney's collecting ducts to water, allowing more water to be reabsorbed into the bloodstream, resulting in more concentrated urine.

Question 1: Calculate the volume of water reabsorbed if a person produces 1.5 litres of urine daily, with 70% of water reabsorbed by the kidneys. Show your working.

Answer: Water reabsorbed = 70% of 1.5 litres = 0.70 x 1.5 = 1.05 litres.

Question 2: A forensic scientist finds that a suspect's urine sample has a concentration of 1500 mOsm/L. If normal human urine ranges from 300 to 900 mOsm/L, what might this indicate about their water intake?

Answer: It suggests the suspect is dehydrated or has a condition causing the kidneys to produce highly concentrated urine, indicating low water intake.

Question 1: Describe a simple experiment to test the effect of different water intake levels on urine concentration in humans. Include the variables and safety precautions.

Answer: Participants would be asked to follow specific water intake levels over a period, with urine samples collected and tested for concentration. Independent variable: water intake volume; dependent variable: urine concentration. Control variables: diet, activity level. Safety precautions include monitoring for dehydration or overhydration, ensuring participants stay within safe limits, and obtaining consent.

Question 1: A forensic investigation reveals that a suspect’s urine output over 24 hours was 0.3 litres with a high concentration of 2000 mOsm/L. What could this indicate about the suspect's hydration status and kidney function?

Answer: This suggests the suspect was severely dehydrated and their kidneys were producing highly concentrated urine, possibly indicating dehydration or a kidney disorder affecting water regulation.

Question 1: Explain how the kidneys help maintain water balance during periods of dehydration. Include the roles of the nephron, collecting duct, and hormones in your answer. (6 marks)

Answer: During dehydration, the body releases more ADH, which increases water reabsorption in the collecting ducts of nephrons, making urine more concentrated. The nephrons filter blood, reabsorbing water back into the bloodstream based on signals from hormones like ADH. This process reduces urine volume and conserves water, helping maintain blood pressure and cell function.

Question 1: In a forensic case, urine analysis shows high concentration but low volume. What might this indicate about the individual's hydration status and possible health conditions?

Answer: It indicates dehydration or a kidney condition that causes the production of concentrated urine despite low urine volume, such as kidney failure or severe fluid restriction.