Final answer:
Setpoints are the physiological values that signify the normal operating range of our bodies and are maintained by negative feedback loops. They can indeed vary between individuals and within an individual over time due to factors like health conditions and environmental influences, making the statement true.
Step-by-step explanation:
The statement that setpoints vary from person to person and may vary within an individual over time is A) True. Setpoints refer to the physiological values around which the normal range fluctuates, such as body temperature and blood pressure. These setpoints are typically maintained by negative feedback loops that return a variable's level back to the normal range.
However, it is possible for an individual's setpoint to change. For instance, the setpoint for blood pressure can increase due to prolonged elevated blood pressure, and the body will adapt to recognize this new setpoint as 'normal', which can have harmful effects on health. Conversely, interventions like medication can lower the setpoint to a healthier level.
Setpoints are important for understanding homeostasis and how our body's physiological conditions are regulated. They are not static and can be influenced by a variety of internal and external factors over an individual's lifetime.