a
One of the major physiological factors that triggers thirst is:
a) a rise in plasma osmolarity
b) a dry mouth from high temperatures
c) becoming overly agitated
d) drinking caffeinated beverages
a
The correct answer is a) a rise in plasma osmolarity.
To understand why a rise in plasma osmolarity triggers thirst, we need to understand what osmolarity is. Osmolarity refers to the concentration of solutes (such as salts and sugars) in a solution. In our bodies, it refers to the concentration of solutes in our bloodstream.
When the concentration of solutes in our bloodstream, or plasma osmolarity, increases, it indicates a higher concentration of solutes and less water content in the blood. This increase in osmolarity is detected by specialized cells called osmoreceptors in the hypothalamus of our brain.
These osmoreceptors are sensitive to changes in osmolarity and trigger the release of a hormone called vasopressin (also known as antidiuretic hormone or ADH). Vasopressin acts on the kidneys to reduce water loss by decreasing the production of urine.
In addition to vasopressin, increased plasma osmolarity also triggers the sensation of thirst. Thirst is a powerful physiological mechanism that drives us to consume fluids and maintain hydration. When the osmoreceptors detect high plasma osmolarity, they send signals to the brain's thirst center, located in the hypothalamus, which then induces the sensation of thirst.
Therefore, a rise in plasma osmolarity is a major physiological factor that triggers thirst. It is the body's way of signaling that it needs more fluids to restore the proper balance of solutes and water in the bloodstream.