Question

Assertion: ADH increases GFR. Reason: ADH cause vasoconstriction thus increase blood pressure, which inturn increase the glomerular blood flow and there by GFR.

Short answer

The statement that ADH increases GFR is partially correct. Under normal hydration, ADH typically leads to a decrease in GFR to conserve water. However, in severe dehydration, vasoconstriction due to the increased levels of ADH may lead to an increase in GFR as the body tries to maintain blood volume and pressure.

Step-by-step solution

Understanding ADH

ADH, or Antidiuretic Hormone, is a hormone that helps kidneys manage the amount of water in the body. It is often released when the body is low on water and needs to conserve it. When released, ADH makes the kidneys reabsorb more water back into the bloodstream rather than excrete it as urine.

Understanding GFR

GFR, or Glomerular Filtration Rate, is the measurement of how much blood is filtered by the kidneys each minute. It is an indication of how well the kidneys are cleaning the blood.

Evaluating the Assertion and Reason

The statement asserted that ADH increases GFR, and the reason given is that ADH causes vasoconstriction which increases blood pressure and in turn, increases the glomerular blood flow and GFR. Although ADH does promote vasoconstriction, this does not directly lead to an increase in GFR. Rather, ADH typically leads to a decrease in GFR because its main role is to conserve water during dehydration, which is done by reducing kidney filtration and thereby reducing the volume of urine produced. But in severe dehydration, vasoconstriction due to ADH can increase GFR as body tries to preserve blood volume and pressure. So the effect of ADH on GFR is variable depending on the body’s hydration status.

Key concepts

Antidiuretic Hormone (ADH)

Antidiuretic Hormone (ADH), also known as vasopressin, plays a critical role in maintaining the body's water balance. It's produced by the hypothalamus and stored in the pituitary gland, ready to be released when the body's water levels fall too low. At its core, ADH helps the kidneys reabsorb water into the bloodstream, thus concentrating the urine and reducing its volume.

During this process, ADH binds to receptors in the kidney's collecting ducts, triggering them to insert aquaporins, which are water channel proteins, into their walls. This mechanism allows water to be reabsorbed from the urine back into the bloodstream, thereby conserving water and increasing the blood's volume and pressure. Understanding the function of ADH is crucial because it not only influences urine concentration but also has wider effects on blood pressure and overall homeostasis.

Glomerular Filtration Rate (GFR)

The Glomerular Filtration Rate (GFR) is a crucial indicator of kidney health and function. It measures the amount of blood that gets filtered by the glomeruli - a network of tiny blood vessels in the kidneys - per minute. This filtration process is essential for removing excess fluids, minerals, and wastes from the bloodstream, which are then excreted as urine.

GFR can be affected by various factors such as hydration level, blood pressure, and blood flow to the kidneys. Certain substances and conditions that impair blood flow can decrease GFR, while those that enhance blood flow can increase it. Due to its importance in kidney function, GFR is often used to detect kidney disease and monitor the progression of renal conditions. A lower GFR can indicate impaired kidney function, requiring prompt medical attention.

Vasoconstriction

Vasoconstriction is the narrowing of the blood vessels, which results from the contraction of the muscular walls of the vessels. This physiological response can be triggered by various factors, including stress, cold temperatures, and certain hormones like ADH. Vasoconstriction's primary effect is on blood pressure; as the blood vessels narrow, resistance to blood flow increases, leading to an increase in blood pressure.

Vasoconstriction plays an adaptive role in the body by redirecting blood to essential organs during times of stress or temperature changes. For example, when you're cold, vasoconstriction reduces blood flow to the skin and extremities to conserve heat. Moreover, in the context of kidney function, vasoconstriction can affect the GFR by altering the blood flow to the kidneys, which in turn impacts the rate at which the kidneys filter blood.

Kidney Function

Kidney function encompasses more than just filtration; it includes the regulation of blood volume, blood pressure, electrolyte levels, and the body's pH balance. The kidneys achieve these tasks through a complex set of processes including filtration, reabsorption, secretion, and excretion.

Every day, your kidneys filter about 120 to 150 quarts of blood to produce about 1 to 2 quarts of urine, which is composed of wastes and extra fluids. This filtration process is selective, ensuring essential substances like glucose and certain salts are reabsorbed while waste products and excess ions are excreted. Functions like adjusting the concentration of urine through ADH are examples of how the kidneys maintain homeostasis, adapting to the body's needs. Healthy kidneys are vital for a well-functioning body, and when kidney function is compromised, it can lead to serious health consequences.