Question 1: The kidneys help maintain water balance in the body by adjusting the concentration of urine. They do this through processes such as filtration, reabsorption, and secretion, which are regulated by hormones like ADH (antidiuretic hormone).

Answer: The kidneys regulate water balance by filtering blood, reabsorbing water and solutes, and secreting waste, with ADH controlling urine concentration.

Question 1: Define osmoregulation and explain its importance in maintaining homeostasis.

Answer: Osmoregulation is the process of controlling water and solute concentrations in the body to maintain stable internal conditions, essential for proper cellular function.

Question 2: Describe the role of ADH in regulating water reabsorption in the kidneys.

Answer: ADH increases the permeability of the kidney’s collecting ducts, allowing more water to be reabsorbed into the blood, thus producing more concentrated urine.

Question 1: Calculate the volume of water lost in millilitres if a person excretes 1.2 litres of urine in a day. (1 litre = 1000 ml)

Answer: 1200 ml

Question 2: A person drinks 2 litres of water and loses 1.8 litres through urine, sweat, and respiration in 24 hours. Calculate their net water gain or loss in millilitres.

Answer: 200 ml gain

Question 3: Using the formula: Water Reabsorption Rate = (Volume of water reabsorbed / Total filtrate) × 100, explain how an increase in ADH affects this rate.

Answer: An increase in ADH increases water reabsorption, raising the percentage of filtrate reabsorbed, leading to more concentrated urine.

Question 1: Describe an experiment to investigate the effect of ADH on urine concentration. Include variables to control and safety precautions.

Answer: An experiment could involve exposing kidney tissue samples to varying concentrations of ADH, measuring urine concentration. Variables include ADH levels (independent), urine concentration (dependent), and temperature, pH (controlled). Safety precautions involve handling chemicals carefully and using appropriate disposal methods.

Question 1: A patient’s urine analysis shows a specific gravity of 1.030. Explain what this indicates about their water balance and ADH activity.

Answer: A specific gravity of 1.030 indicates concentrated urine, suggesting high ADH activity and the body conserving water, possibly due to dehydration.

Question 1: Explain how the kidneys help maintain water balance during dehydration and overhydration. Include the roles of filtration, reabsorption, and hormones such as ADH. (6 marks)

Answer: During dehydration, the kidneys respond by increasing ADH secretion, which makes the collecting ducts more permeable, allowing more water to be reabsorbed and producing concentrated urine. Conversely, during overhydration, ADH secretion decreases, reducing water reabsorption, resulting in dilute urine. The processes of filtration at the glomerulus, selective reabsorption in the tubules, and hormonal regulation ensure water balance is maintained in the body.

Question 1: Explain how knowledge of water balance regulation by the kidneys can be applied in treating conditions like diabetes insipidus.

Answer: Understanding kidney water regulation helps in diagnosing and treating diabetes insipidus, a condition where ADH production or response is impaired, leading to excessive dilute urine. Treatments may involve hormone therapy or managing fluid intake to maintain water balance.