Question

How does ADH decrease the loss of water through the kidneys? a. ADH increases water reaborption in the collecting ducts. b. ADH decreases the amount of blood flowing through the kidneys. c. ADH increases water reabsorption in the proximal tubule. d. ADH decreases water excretion in the loop of Henle.

Short answer

a. ADH increases water reabsorption in the collecting ducts.

Step-by-step solution

- Understand the Role of ADH

ADH stands for Antidiuretic Hormone, which is also known as vasopressin. It helps regulate water balance in the body by controlling the amount of water the kidneys reabsorb as they filter out waste from the blood.

- Identify ADH's Primary Target

The primary effect of ADH is on the kidney's collecting ducts. ADH increases the permeability of the collecting ducts to water, allowing more water to be reabsorbed back into the bloodstream.

- Evaluate Each Option

a. ADH increases water reabsorption in the collecting ducts (Correct: This is the main action of ADH).b. ADH decreases the amount of blood flowing through the kidneys (Incorrect: ADH does not significantly affect blood flow to the kidneys).c. ADH increases water reabsorption in the proximal tubule (Incorrect: The primary site of action is the collecting ducts, not the proximal tubule).d. ADH decreases water excretion in the loop of Henle (Incorrect: The loop of Henle is not the main site of water reabsorption influenced by ADH).

Key concepts

antidiuretic hormone

Antidiuretic hormone, often abbreviated as ADH, is crucial for regulating the body’s water balance. Also known as vasopressin, this hormone is produced in the hypothalamus and released by the pituitary gland. ADH's primary role is to maintain the balance of fluids by controlling how much water the kidneys need to retain. The more ADH is released, the more water the kidneys reabsorb into the bloodstream. This helps to conserve water in the body and concentrate the urine. By carefully managing water reabsorption, ADH helps to prevent dehydration and maintain optimal blood pressure.

kidneys

The kidneys play a vital role in filtering blood and maintaining homeostasis. These bean-shaped organs, located on either side of the spine, filter out waste products and excess substances from the bloodstream. Not only do they excrete these wastes as urine, but they also regulate essential aspects of the body’s internal environment. This includes electrolyte balance, acid-base balance, and fluid volume. The kidneys interact with multiple hormones, including ADH, to fine-tune the body’s water and electrolyte levels. Their structure consists of various parts, including nephrons, which are the functional units responsible for urine formation. These nephrons further contain structures like the glomerulus, proximal tubule, loop of Henle, distal tubule, and collecting ducts.

collecting ducts

The collecting ducts are essential pathways in the kidneys where the final concentration of urine is regulated. These ducts receive urine from the nephrons and are the primary target for ADH action. ADH increases the permeability of the walls of the collecting ducts to water. This means that more water can be reabsorbed back into the bloodstream as it passes through these ducts. The result is more concentrated urine and less water loss. By controlling the amount of water reabsorbed in the collecting ducts, ADH helps to ensure that the body retains enough water to maintain vital physiological functions.

water balance

Water balance in the body is the careful management of water intake and output. It is crucial for maintaining homeostasis and proper physiological function. The body's total water volume must remain relatively constant; otherwise, it can lead to conditions like dehydration or overhydration. The balance is regulated by several mechanisms, with ADH being a key player. When the body is dehydrated, ADH levels increase, signaling the kidneys to reabsorb more water and produce less urine. Conversely, when there is an excess of water, ADH levels decrease, allowing more water to be excreted. Alongside ADH, other factors such as thirst, kidney function, and the presence of other electrolytes play significant roles in maintaining water balance.