Certified in Public Health (CPH) Practice Exam

What is the primary reason the body maintains blood glucose levels within a narrow range?

1. Glucose is used for energy by brain cells at all times

2. Glucose is used by muscles for energy during exercise

3. Glucose is the central substance of carbohydrate metabolism

4. Glucose is converted into glycogen

The correct answer is: Glucose is used for energy by brain cells at all times

The primary reason the body maintains blood glucose levels within a narrow range is that glucose is essential for energy production, particularly for brain cells, which rely on it continuously. The brain is highly sensitive to fluctuations in glucose levels because it does not store glucose and must receive a consistent supply from the bloodstream. Low glucose levels can impair cognitive function and lead to symptoms such as confusion or loss of consciousness, while excessively high levels can lead to complications such as hyperglycemia. The body's regulatory mechanisms, involving hormones like insulin and glucagon, work to stabilize blood glucose so that the brain always has access to the energy it requires. While muscles do use glucose for energy during exercise, and glucose is central to carbohydrate metabolism, the critical factor for maintaining blood glucose levels revolves around the brain's need for a steady supply of this vital energy source. Additionally, while glycogen conversion is an important process for energy storage, it is not the primary reason for maintaining strict blood glucose levels.