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6. (a) Hyperthyroidism is caused by an overactive thyroid gland - Edexcel - GCSE Biology Combined Science - Question 6 - 2020 - Paper 1
Question 6
6. (a) Hyperthyroidism is caused by an overactive thyroid gland. Figure 9 shows a person with a normal thyroid gland and a person with hyperthyroidism. (i) State o... show full transcript
Worked Solution & Example Answer:6. (a) Hyperthyroidism is caused by an overactive thyroid gland - Edexcel - GCSE Biology Combined Science - Question 6 - 2020 - Paper 1
Step 1
Step 3
Explain how negative feedback, involving the thyroid gland, controls metabolic rate.
Answer
Negative feedback involving the thyroid gland regulates metabolic rate through a series of hormonal responses.
- When levels of thyroxine are low, the hypothalamus secretes Thyrotropin-Releasing Hormone (TRH).
- TRH stimulates the pituitary gland to release Thyroid-Stimulating Hormone (TSH).
- TSH prompts the thyroid gland to produce thyroxine.
- Elevated levels of thyroxine then inhibit the release of both TRH and TSH, ensuring that thyroxine levels remain within an optimal range.
Step 4
Explain how hormones control the menstrual cycle.
Answer
Hormones play a crucial role in regulating the menstrual cycle through various phases.
- The cycle begins with the release of Follicle-Stimulating Hormone (FSH) by the pituitary gland, stimulating the ovaries to mature follicles.
- As follicles develop, they produce estrogen, leading to the thickening of the uterine lining.
- A surge in Luteinizing Hormone (LH) triggers ovulation, releasing an egg from a mature follicle.
- Post-ovulation, the ruptured follicle becomes the corpus luteum, producing progesterone to further prepare the uterine lining for implantation.
- If fertilization does not occur, hormone levels drop, leading to menstruation.