IGCSE Biology glossary
Adrenaline
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Definition
A hormone produced by the adrenal glands in response to stress or danger. Adrenaline increases heart rate, breathing rate and blood glucose concentration, preparing the body for a 'fight or flight' response by directing more oxygen and glucose to muscles.
What to include in an exam answer
Adrenaline is a hormone example for the fight-or-flight response. Its effects include: increased heart rate, increased breathing rate, glycogen converted to glucose, and blood redirected to muscles.
Example in context
Explain how adrenaline prepares the body for exercise (3 marks): Adrenaline increases the heart rate, so blood carrying oxygen and glucose reaches muscles faster. It increases breathing rate, so more oxygen enters the blood. It stimulates the liver to convert glycogen to glucose, raising blood glucose for respiration.
Related syllabus topic
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