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Explain how hormone activity maintains water and salt levels in the blood. - HSC - SSCE Biology - Question 22 - 2008 - Paper 1
Question 22
Explain how hormone activity maintains water and salt levels in the blood.
Worked Solution & Example Answer:Explain how hormone activity maintains water and salt levels in the blood. - HSC - SSCE Biology - Question 22 - 2008 - Paper 1
Step 1
Hormones involved in maintaining water levels
Answer
Hormones play a crucial role in regulating water levels in the blood, primarily through the action of antidiuretic hormone (ADH). ADH, produced in the hypothalamus and released from the posterior pituitary gland, acts on the kidneys to promote water reabsorption. When blood water levels are low, ADH is secreted, causing the kidneys to reabsorb more water from urine, thus concentrating the urine and increasing blood volume.
Step 2
Hormones involved in maintaining salt levels
Answer
To maintain salt levels, aldosterone is the key hormone. Produced by the adrenal cortex, aldosterone signals the kidneys to increase the reabsorption of sodium. When sodium levels are low or when there is a decrease in blood volume, aldosterone secretion increases, helping to retain sodium in the body, which in turn draws water back into the bloodstream, raising blood pressure and volume.
Step 3
Explanation of reabsorption process
Answer
Reabsorption refers to the process by which the kidneys filter blood and then reclaim necessary substances. Under the influence of ADH, the collecting ducts of the kidneys become more permeable to water, allowing more water to be reabsorbed back into the bloodstream. With aldosterone, sodium reabsorption occurs primarily in the distal convoluted tubules and collecting ducts. The increase in sodium concentration promotes osmotic reabsorption of water, assisting in maintaining both salt and water homeostasis in the blood.