Question

If a person were to drink an excess of water, what would happen as a result? a. The GFR would decrease. b. The concentration of ADH in the blood would decrease. c. The concentration of ADH in the blood would increase. d. GFR would increase. e. Both b and d would occur.

Short answer

The correct answer is 'e'. Both b and d would occur.

Step-by-step solution

Analyze the implication on GFR

When the body intake of water is high, it needs to eliminate the excess water. The kidneys would respond to this by increasing the GFR. Hence, it means GFR should increase in such a case.

Analyze the implication on ADH

ADH plays a significant role in regulating water in the body; it reduces urine production, promoting water reabsorption in kidneys. In a hydrated state (i.e., when water intake is high), less ADH is required. As a result, the concentration of ADH in the blood would decrease.

Choose the correct answer

From steps 1 and 2 we realize that, after drinking an excess amount of water, GFR would increase (option d) and the concentration of ADH in the blood would decrease (option b). Therefore, the correct answer is option 'e', both b and d would occur.

Key concepts

Glomerular Filtration Rate

The glomerular filtration rate (GFR) reflects the amount of blood filtered by the kidneys per minute. This filtration process is crucial for removing waste products from the body and regulating fluid balance.
It represents a key indicator of renal function. When someone drinks too much water, the body must adjust to maintain balance. This is because excess water increases blood plasma volume. To maintain homeostasis, the kidneys respond by filtering more blood. As a result, this increased filtration pup helps the body reduce the excess fluid.
The increased GFR allows the body to process and remove excess water more quickly, preventing potential water overload or edema. The body tightly regulates GFR to ensure it does not filter out too many vital substances. Having an adaptable GFR is essential for maintaining overall body balance.

Antidiuretic Hormone

Antidiuretic hormone (ADH) is vital for maintaining water balance in the body. ADH influences kidneys by promoting water reabsorption back into the bloodstream.
Its release from the posterior pituitary gland is primarily triggered by high plasma osmolarity or low blood volume. When you are dehydrated, more ADH is released, which leads to less urine production. Conversely, when you consume an excess of water, ADH secretion decreases. This reduction allows more water to exit the body through urine.
By lowering ADH levels, the body prompts the kidneys to excrete more water, helping restore fluid balance. ADH regulation demonstrates how the body manages water content judiciously, adapting hormone levels to meet current hydration needs. This dynamic response is key to maintaining a stable internal environment.

Water Balance

Maintaining proper water balance is vital for many physiological processes. The balance is between intake and the amount of water lost through various body processes.

Having too much water in the body can dilute essential electrolytes, which include sodium and potassium. This can disrupt cellular function. To prevent this, the body regulates both GFR and ADH levels dynamically. - **Higher Water Intake:** - GFR increases to filter excess fluid quickly. - ADH secretion decreases to permit loss of additional water through urine.
- **Lower Water Intake:** - GFR may reduce to conserve fluid. - ADH secretion increases to keep more water in the body. By adjusting these responses, the body works to maintain equilibrium in water levels, ensuring that cells function optimally.

Renal Function

Renal function refers to how well the kidneys perform key processes like filtering blood, maintaining fluid balance, and excreting waste.
Good renal function is essential for regulating blood pressure, keeping electrolyte levels stable, and managing fluid balance. Key functions of the kidneys include: 1. **Filtration:** Removing waste and excess substances from the blood. 2. **Reabsorption:** Returning needed substances and water back to the blood. 3. **Secretion:** Actively transporting additional waste for excretion. When fluid intake is high, like after an excess water consumption, the kidneys adjust by increasing the GFR and decreasing ADH levels. This way, the kidneys work efficiently to restore fluid balance by excreting more urine.
Efficient renal function ensures that even under varying conditions, the body can maintain homeostasis, proving the importance of kidneys in vital regulation tasks.