Which of the following is not an example of homeostasis?
a) After plunging into icy-cold water, Gary’s core body temperature rapidly drops.
b)While exercising, Julia’s heart rate and breathing increase to balance the increased oxygen use by her muscle cells.
c) On a hot day, to prevent dehydration, Martin’s kidneys remove very little water from his blood.
d)After eating a candy bar, April’s pancreas secretes insulin, which removes the excess blood sugar.
The Correct Answer and Explanation is:
The correct answer is a) After plunging into icy-cold water, Gary’s core body temperature rapidly drops.
Explanation:
Homeostasis is the process by which the body maintains a stable internal environment, despite changes in external conditions. This involves regulating variables such as temperature, pH, and glucose levels within a narrow range, which is vital for optimal body function. Let’s break down the options:
- Option a: After plunging into icy-cold water, Gary’s core body temperature rapidly drops.
- This is not an example of homeostasis. While the body does try to regulate temperature (for example, by shivering or constricting blood vessels to conserve heat in cold environments), this statement describes the opposite of homeostasis. A drop in core body temperature indicates that the body’s temperature regulation mechanisms are not able to counter the rapid cooling effect of the icy water, leading to a deviation from the body’s normal temperature set point. This is not the body maintaining homeostasis, but rather a failure to do so under extreme conditions.
- Option b: While exercising, Julia’s heart rate and breathing increase to balance the increased oxygen use by her muscle cells.
- This is an example of homeostasis. During exercise, muscle activity increases, requiring more oxygen. To maintain homeostasis, the body compensates by increasing heart rate and respiration rate, which helps deliver more oxygen to the muscles. This is an adaptive response to balance the increased oxygen demand, ensuring proper cellular function.
- Option c: On a hot day, to prevent dehydration, Martin’s kidneys remove very little water from his blood.
- This is an example of homeostasis. On hot days, the body conserves water to avoid dehydration. The kidneys play a crucial role in this process by adjusting the amount of water reabsorbed into the bloodstream, minimizing water loss through urine. This is an example of the body maintaining fluid balance.
- Option d: After eating a candy bar, April’s pancreas secretes insulin, which removes the excess blood sugar.
- This is an example of homeostasis. After consuming sugar, blood glucose levels rise. The pancreas releases insulin to promote the uptake of glucose by cells, reducing blood sugar levels to a normal range. This is a clear example of homeostasis, as the body works to maintain blood glucose levels within a healthy range.
In summary, Option a represents a scenario where homeostasis is not maintained, while the other options depict situations where homeostasis is actively regulated.