OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

What is the primary function of adrenaline in the body?

1. Stimulating appetite

2. Preparing the body for 'fight or flight'

3. Regulating sleep patterns

4. Controlling body temperature

The correct answer is: Preparing the body for 'fight or flight'

The primary function of adrenaline, also known as epinephrine, is to prepare the body for 'fight or flight' responses. When faced with a stressful situation, the adrenal glands release adrenaline into the bloodstream, which triggers a series of physiological changes. This includes an increase in heart rate, dilation of the air passages, and heightened alertness, all of which help the body respond quickly to threats. Additionally, adrenaline boosts the availability of energy sources by increasing blood sugar levels and enhancing muscle strength and performance. This state of heightened arousal and readiness is crucial for survival in dangerous situations, allowing individuals to either confront a threat or escape from it effectively. The other options represent functions that are not primarily associated with adrenaline. For instance, while appetite regulation is influenced by other hormones, adrenaline is not directly responsible for stimulating appetite. Similarly, sleep patterns are primarily controlled by hormones like melatonin, and body temperature regulation is managed by different mechanisms involving the hypothalamus, rather than being a direct action of adrenaline.