Which of the following hormones is suddenly secreted into the bloodstream of a frightened person?

Step 1: Analyze the question The question asks which hormone is released suddenly when a person is frightened. This is the "fight or flight" response.

Step 2: Explain the concept When a person is scared, the brain (hypothalamus) signals the sympathetic nervous system. This stimulates the adrenal medulla, which sits on top of the kidneys, to release adrenaline (epinephrine) into the blood very quickly.

Adrenaline prepares the body for emergency action by:

• Increasing heart rate and breathing rate
• Raising blood glucose, since glycogen is converted to glucose in the liver
• Diverting blood to the muscles and away from the skin and gut (so the person may look pale)
• Dilating the pupils
• Making hairs stand on end

Step 3: Check each option

• A. Insulin: Made by the pancreas. It lowers blood sugar, so it is the opposite of what is needed in an emergency.
• B. Adrenaline: Released in sudden emergencies such as fear, anger or danger. ✔
• C. Thyroxine: Made by the thyroid gland. It controls the metabolic rate over the long term and is not released suddenly.
• D. Parathormone: Made by the parathyroid glands. It regulates calcium levels in the blood and has nothing to do with fear.

Step 4: Answer The correct answer is B. adrenaline.

Exam tip: Remember "Adrenaline = Alarm, Action". Whenever you see fear, anger, danger, fight or flight, think adrenaline. Also remember that adrenaline acts fast, while thyroxine acts slowly and steadily.