Questions: Which is NOT an example of homeostasis? Increased estrogen during the menstrual cycle increases the number of progesterone receptors in the uterus. Increased blood pressure in the aorta stimulates mechanisms to lower blood pressure. Increased blood sugar stimulates the release of a hormone from the pancreas that stimulates the liver to store blood sugar. Decreased body temperature stimulates a neural response that increases body temperature. Increased blood calcium levels stimulates the release of a hormone that lowers blood calcium levels.

The answer is the first one: Increased estrogen during the menstrual cycle increases the number of progesterone receptors in the uterus.

Explanation for each option:

1. Increased estrogen during the menstrual cycle increases the number of progesterone receptors in the uterus.

   • This is NOT an example of homeostasis. This process is part of the normal physiological changes during the menstrual cycle, but it does not involve maintaining a stable internal environment. Instead, it is a preparatory change for potential pregnancy.

2. Increased blood pressure in the aorta stimulates mechanisms to lower blood pressure.

   • This is an example of homeostasis. The body is responding to high blood pressure by activating mechanisms to bring it back to normal levels, maintaining internal stability.

3. Increased blood sugar stimulates the release of a hormone from the pancreas that stimulates the liver to store blood sugar.

   • This is an example of homeostasis. The release of insulin from the pancreas in response to high blood sugar helps lower blood sugar levels, maintaining balance.

4. Decreased body temperature stimulates a neural response that increases body temperature.

   • This is an example of homeostasis. The body responds to low temperature by generating heat to maintain a stable internal temperature.

5. Increased blood calcium levels stimulates the release of a hormone that lowers blood calcium levels.

   • This is an example of homeostasis. The release of calcitonin in response to high calcium levels helps reduce calcium levels, maintaining balance.

In summary, the first option is not an example of homeostasis, as it involves a physiological change rather than a regulatory mechanism to maintain internal stability.