What part of the brain is primarily responsible for monitoring blood

glucose levels and causing chemical reactions to spur us to eat when

glucose levels are low?

Ventromedial hypothalamus.

Explanation:

Ventromedial hypothalamus is a part of the hypothalamus in the brain that is responsible for controlling blood glucose levels. It stimulate the pancreas to release hormones like insulin which stabilize the blood glucose levels.

The hypothalamus also stimulate the adrenal gland to make and release cortisol in the blood which increase blood glucose levels when it is low.