Massachusetts Comprehensive Assessment System (MCAS) Biology Practice Test

What is an example of homeostasis in the human body?

1. Hormonal changes during stress

2. Heart rate increasing when a person exercises

3. Temperature fluctuations in the body

4. Virtual reality simulations of the body

The correct answer is: Heart rate increasing when a person exercises

Homeostasis refers to the processes that maintain a stable internal environment within an organism despite external changes. The regulation of heart rate during exercise is a prime example of homeostasis in action. When a person engages in physical activity, their body's demand for oxygen and nutrients increases. To meet this increased demand, the heart rate elevates to pump more blood throughout the body. This increase ensures that skeletal muscles receive adequate oxygen to produce energy, demonstrating how the body adjusts its systems to maintain balance and support metabolic functions. Other options, while related to physiological responses, do not exemplify homeostasis in the same way. Hormonal changes during stress are part of the body's response to external stimuli but do not illustrate a direct compensatory mechanism for self-regulation. Temperature fluctuations, although they occur, do not represent homeostasis; instead, maintaining a stable body temperature would be a more accurate reflection of homeostatic processes. Virtual reality simulations, while they may provide insights into bodily functions, do not pertain to the biological concept of homeostasis.