AEMCA Practice Exam

What physiological reaction occurs when plasma solute concentrations increase?

1. Decreased thirst response

2. Activation of thirst mechanism

3. Impaired kidney functions

4. Increased urination

The correct answer is: Activation of thirst mechanism

When plasma solute concentrations increase, it typically indicates a higher level of substances like salts or other solutes in the blood, which leads to a condition known as hyperosmolarity. The body responds to this change by activating the thirst mechanism. This physiological response is primarily controlled by osmoreceptors located in the hypothalamus, which detect changes in osmotic pressure. When these osmoreceptors sense that the plasma solute concentration is above the normal range, they trigger the sensation of thirst, prompting the individual to drink fluids. This is an essential regulatory mechanism aimed at restoring homeostasis by diluting the plasma solutes back to normal levels through increased fluid intake. In addition, activation of the thirst mechanism plays a crucial role in preventing dehydration and ensuring adequate hydration status in the body. Understanding the body's regulatory responses, such as the activation of the thirst mechanism, is vital for recognizing how it maintains fluid balance in varying physiological conditions.