Negative feedback (HT only) — AQA GCSE Biology
Test yourself on Negative feedback (HT only) with AQA GCSE practice questions.
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Negative feedback (HT only) explained
Thyroxine and adrenaline are hormones that help the body respond to change.
Read the full explanation
Thyroxine is produced by the thyroid gland and controls the metabolic rate, so it affects how quickly cells release energy from food. Its level is controlled by negative feedback: if thyroxine is too low, the hypothalamus and pituitary gland stimulate the thyroid to release more; if it is too high, release is reduced. Adrenaline is produced by the adrenal glands in times of fear or stress. It increases heart rate and boosts delivery of oxygen and glucose to the brain and muscles, preparing the body for ‘flight or fight’. Together they show how hormones maintain stable internal conditions and enable rapid responses.
Your focus
- Describe the role of thyroxine in controlling metabolic rate.
- Explain how negative feedback controls thyroxine levels.
- Explain how adrenaline prepares the body for ‘flight or fight’.
Negative feedback (HT only) exam tips
Marking Points
- State that thyroxine is produced by the thyroid gland and controls the metabolic rate.
- Explain that thyroxine levels are controlled by negative feedback involving the hypothalamus and pituitary gland.
- State that adrenaline is produced by the adrenal glands in times of fear or stress.
- Explain that adrenaline increases heart rate and boosts delivery of oxygen and glucose to the brain and muscles.
- Link adrenaline to preparation for ‘flight or fight’ and thyroxine to long-term control of metabolism.
Examiner Tips
- 💡Name the gland and the hormone together in every answer to avoid confusion.
- 💡For thyroxine, mention negative feedback and the role of the hypothalamus and pituitary gland.
- 💡For adrenaline, link the increased heart rate to faster delivery of oxygen and glucose to the brain and muscles.
Common Mistakes
- Confusing the glands: thyroxine comes from the thyroid gland, while adrenaline comes from the adrenal glands; correct this by naming each gland with its hormone.
- Thinking adrenaline lowers heart rate; correct this by stating that adrenaline increases heart rate.
- Describing thyroxine as a fast stress hormone; correct this by explaining that thyroxine controls metabolic rate and is regulated by negative feedback.