Question

In your home, a thermostat monitors the ambient temperature. If the ambient temperature drops below a set point the furnace turns on and then heats the house. When the thermostat detects that the temperature is back at the set point it turns the furnace off. Which of the below physiological examples is the control of your house temperature most similar to?

All of these are similar to the example of the house thermostat, since they are examples of negative feedback control

In humans, the control of carbon dioxide levels in the blood

In humans, the control of calcium levels in the blood

In humans, the control of glucose levels in the blood

Answer 1

From the above example, it is clear that the case of thermostat which monitors the ambient temperature is very sensitive. So from the above 3 options, the most sensitive control/regulation in our body can be that of blood CO₂ level. A sudden increase in the CO₂ level of blood will result in oxygen deprivation to vital organs, which can be fatal to the body. Carbon dioxide is transported in the blood as bicarbonate ions and dissolved in blood plasma. Increased dissolution of carbon dioxide in the blood will cause increased acidity(decreased pH). The decrease in pH means there is a lack of oxygen, which is fatal to the body. So the body recognizes it and immediately decrease blood bicarbonate ions level/ CO₂ level dissolution and hence regulate it.

According to your query, this is similar to the case of thermostat which monitors the ambient temperature since the thermostat detects that the temperature is back at the set point it turns the furnace off.