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Hyperthyroidism is caused by an overactive thyroid gland - Edexcel - GCSE Biology Combined Science - Question 6 - 2020 - Paper 1
Question 6
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 one effec... show full transcript
Worked Solution & Example Answer:Hyperthyroidism is caused by an overactive thyroid gland - Edexcel - GCSE Biology Combined Science - Question 6 - 2020 - Paper 1
Step 1
Step 2
Step 3
Explain how negative feedback, involving the thyroid gland, controls metabolic rate.
Answer
The regulation of metabolic rate through the thyroid gland involves a negative feedback mechanism:
- Low levels of thyroxine in the blood trigger the production of Thyrotropin-Releasing Hormone (TRH) in the hypothalamus.
- TRH stimulates the release of Thyroid-Stimulating Hormone (TSH) from the pituitary gland.
- TSH then encourages the thyroid gland to produce more thyroxine.
- As thyroxine levels rise, they inhibit the production of TRH and TSH, effectively decreasing further thyroxine production and maintaining homeostasis.
Step 4
Explain how hormones control the menstrual cycle.
Answer
The menstrual cycle is primarily regulated by hormones such as FSH, LH, estrogen, and progesterone:
- Follicle-Stimulating Hormone (FSH) stimulates the growth of ovarian follicles and the production of estrogen in the ovaries.
- Rising estrogen levels lead to a surge in Luteinizing Hormone (LH), which triggers ovulation.
- After ovulation, the ruptured follicle transforms into the corpus luteum, which secretes progesterone.
- Progesterone prepares the uterine lining for potential implantation of a fertilized egg; if fertilization does not occur, hormone levels fall, leading to menstruation.