Photo AI
9 (a) Hyperthyroidism is caused by an overactive thyroid gland - Edexcel - GCSE Biology - Question 9 - 2020 - Paper 1
Question 9
9 (a) Hyperthyroidism is caused by an overactive thyroid gland. Figure 14 shows a person with a normal thyroid gland and a person with hyperthyroidism. (i) State o... show full transcript
Worked Solution & Example Answer:9 (a) Hyperthyroidism is caused by an overactive thyroid gland - Edexcel - GCSE Biology - Question 9 - 2020 - Paper 1
Step 1
Step 3
Explain how negative feedback, involving the thyroid gland, controls metabolic rate.
Answer
Negative feedback is a crucial mechanism for regulating hormonal levels in the body. In the case of the thyroid gland, when the metabolic rate increases, the levels of thyroid hormones (T3 and T4) in the blood also rise. This increase sends signals to the hypothalamus and the pituitary gland, which leads to a decrease in Thyroid Stimulating Hormone (TSH) production. Consequently, lower TSH results in decreased thyroid hormone production, helping to stabilize the metabolic rate back to normal levels.
Step 4
Explain how hormones control the menstrual cycle.
Answer
The menstrual cycle is regulated by a complex interplay of hormones. The cycle starts with the release of Follicle Stimulating Hormone (FSH) from the pituitary gland, stimulating the growth of ovarian follicles. As the follicles mature, they produce estrogen, which promotes the thickening of the uterine lining (endometrium). Around the midpoint of the cycle, a surge in Luteinizing Hormone (LH) triggers ovulation, releasing an egg from the ovary. After ovulation, the empty follicle transforms into the corpus luteum, which secretes progesterone to maintain the uterine lining. If fertilization does not occur, progesterone levels drop, resulting in menstruation as the uterine lining is shed.