Which of the following describes a negative feedback loop?
When the heart rate is too high, the body sends hormones that continually increase the heart rate higher.
When a pregnant woman is in labor, the body sends hormones that increase the intensity of contractions, which then increases the secretion of the same hormones.
When blood sugar is too low, the body sends hormones that raise blood sugar until it reaches a typical level and hormone secretion slows.
When a person is jogging, the body sends hormones that continually decrease the rate of oxygen supply to the legs
The Correct Answer and Explanation is:
The correct answer is: When blood sugar is too low, the body sends hormones that raise blood sugar until it reaches a typical level and hormone secretion slows.
Explanation
A negative feedback loop is a fundamental concept in homeostasis, which is the process through which biological systems maintain stability while adjusting to conditions that are optimal for survival. In a negative feedback loop, a change in a physiological variable triggers a response that counteracts the initial change, returning the system to its set point or normal range.
In the context of blood sugar regulation, when blood sugar levels drop too low (a condition known as hypoglycemia), the body responds by releasing hormones such as glucagon from the pancreas. Glucagon signals the liver to convert stored glycogen into glucose and release it into the bloodstream, thereby increasing blood sugar levels. This increase continues until the blood sugar levels reach a normal range. Once the desired blood sugar level is achieved, the secretion of glucagon slows down, demonstrating how negative feedback works to maintain homeostasis.
In contrast, the other options describe positive feedback mechanisms, where the response to a stimulus enhances or amplifies the initial change rather than counteracting it:
- Heart Rate Increase: If heart rate is too high, sending more hormones to increase it further would be an example of positive feedback, not negative feedback.
- Labor Contractions: During labor, the release of hormones like oxytocin increases contractions, further stimulating more oxytocin release. This is a classic example of positive feedback.
- Oxygen Supply During Jogging: Decreasing the rate of oxygen supply would not help maintain homeostasis; it would be counterproductive during physical activity.
In summary, the regulation of blood sugar through hormone release exemplifies a negative feedback loop, as it involves a corrective mechanism that brings the physiological variable back to its optimal state.