Why does dehydration elevate plasma osmolality leading to increased water reabsorption in the kidneys?

💡 Explanation

Elevated plasma osmolality triggers the release of antidiuretic hormone (ADH), because ADH increases the permeability of the collecting ducts in the kidneys to water. Therefore, more water is reabsorbed back into the bloodstream, rather than being excreted in urine, decreasing plasma osmolality.

• If a patient undergoing chemotherapy develops a non-healing skin ulcer, which mechanism primarily impedes wound closure?
• An elderly patient with chronic hypertension experiences increased arterial stiffness, reducing baroreceptor sensitivity. What happens to aldosterone secretion due to these changes?
• If a researcher introduces a novel compound inhibiting NF-κB activation in macrophages during an inflammatory response to LPS (lipopolysaccharide), which consequence follows?
• If a neurotoxin selectively blocks Piezo2 channels in human Pacinian corpuscles, which sensory effect follows?
• A patient presents with dehydration after prolonged vomiting. Which mechanism explains why the kidneys initially reduce urine output, but the urine becomes more concentrated with increased sodium?
• A hiker stranded in a blizzard experiences extreme hypothermia. Why does shivering become less effective below a core body temperature of 30°C (86°F)?