Problem 8 - Biology: The Dynamic Science

Question

Deficient water levels in humans are prevented by: a. osmoreceptors on the hypothalamus that detect decreases in salt concentrations. b. the hypothalamus stimulating the posterior pituitary to secrete a hormone that allows the collecting ducts and distal convoluted tubules to be permeable to water. c. inhibiting ADH, which causes a rise in osmolarity of ex. tracellular fluids. d. producing dilute urine. e. drinking alcohol, which stimulates aldosterone to raise the osmolarity of body fluids.

Step-by-Step Solution

Answer

The correct answer is b) The hypothalamus stimulates the posterior pituitary to secrete a hormone that allows the collecting ducts and distal convoluted tubules to be permeable to water.

Step 1: Understand the options provided

This task is a multiple-choice question. Therefore, the first step is to go through and assess each answer choice one by one to determine which ones could be correct. This requires a basic understanding of how the body maintains water balance and the role of the hypothalamus, osmoreceptors and ADH in this process.

Step 2: Analyze each choice

Answer a) suggests that osmoreceptors respond to decreases in salt concentrations. However, osmoreceptors in the hypothalamus primarily respond to an increase in the salt concentration or a decrease in water concentration within the blood. So, this is incorrect. Answer b) proposes that a hormone from the posterior pituitary gland makes the collecting ducts and distal convoluted tubules permeable to water. This hormone is ADH, and its primary function is indeed to increase the permeability of the kidney tubules to conserve water within the body. So, this answer is correct. Answer c) ALso involves ADH. But Inhibiting ADH would cause a rise in the osmolarity of the extracellular fluids by decreasing water reabsorption, leading to water deficiency, not preventing it. So, this is incorrect. Answer d) suggests that producing dilute urine prevents water deficiency. This is incorrect because dilute urine typically results from drinking large amounts of water, not from a mechanism to prevent water deficiency. Answer e) implies that alcohol raises the osmolarity of body fluids, which is false. Alcohol actually inhibits the secretion of ADH, causing an increase in urine output and potentially leading to dehydration.

Step 3: Finalize

Based on the understanding and analysis of how the body maintains water balance, choice b) is true. The hypothalamus stimulates the posterior pituitary to secrete a hormone (ADH) that helps in water reabsorption by kidney tubules and thus prevents water deficiency in the body.