Optometry Admission Test (OAT) Practice

What is a primary effect of epinephrine and norepinephrine?

1. Lower heart rate

2. Decrease blood glucose levels

3. Increase blood glucose levels

4. Stimulate glycogen synthesis

The correct answer is: Increase blood glucose levels

Epinephrine and norepinephrine are key hormones and neurotransmitters that play a critical role in the body's stress response, often referred to as the "fight or flight" response. One of their primary effects is to increase blood glucose levels, which is crucial for supplying energy to various tissues, especially during times of stress or physical exertion. When released into the bloodstream, epinephrine triggers the liver to break down glycogen into glucose, a process known as glycogenolysis. This results in a rapid increase in blood glucose concentration, providing immediate energy to muscles and other tissues that may need it for quick action. Additionally, these hormones promote gluconeogenesis, the synthesis of glucose from non-carbohydrate sources, further contributing to elevated glucose levels. The other options do not effectively describe the primary physiological responses associated with epinephrine and norepinephrine. Lowering heart rate is typically associated with parasympathetic activity, while stimulating glycogen synthesis contradicts the action these hormones promote on glucose mobilization. Decreasing blood glucose levels is not a direct effect of epinephrine and norepinephrine, as their role is primarily to mobilize energy rather than reduce it.