What are the effects of dehydration on nephron function?

Dehydration can lead to reduced glomerular filtration rate, increased reabsorption of water and concentrated urine production.

Dehydration is a condition characterised by an insufficient amount of water in the body. This can have a significant impact on the function of nephrons, the microscopic functional units of the kidney responsible for the formation of urine. One of the primary effects of dehydration on nephron function is a reduction in the glomerular filtration rate (GFR). The GFR is the rate at which blood is filtered in the glomeruli of the kidneys. When the body is dehydrated, there is less blood volume and therefore less pressure to push blood through the glomeruli, resulting in a lower GFR.

In addition to affecting the GFR, dehydration also influences the reabsorption of water in the nephrons. Normally, the nephrons reabsorb water from the filtrate back into the bloodstream to maintain the body's fluid balance. However, when the body is dehydrated, the kidneys respond by increasing the reabsorption of water to conserve as much water as possible. This is primarily achieved through the release of the hormone vasopressin (also known as antidiuretic hormone or ADH), which makes the walls of the collecting ducts more permeable to water, allowing more water to be reabsorbed back into the bloodstream.

Finally, dehydration can lead to the production of concentrated urine. As more water is reabsorbed from the filtrate, the remaining urine becomes more concentrated with waste products. This is why urine tends to be darker and more concentrated when a person is dehydrated. In severe cases, the high concentration of waste products can lead to the formation of kidney stones.

In summary, dehydration can significantly affect nephron function by reducing the glomerular filtration rate, increasing the reabsorption of water, and leading to the production of concentrated urine. These changes are part of the body's adaptive response to conserve water and maintain fluid balance, but they can also lead to potential health problems if dehydration is severe or prolonged.