Edexcel GCSE Biology Topic 7 Animal coordination, control and homeostasis: a complete overview of hormones, the menstrual cycle, blood glucose, thermoregulation and the kidney

What Topic 7 actually demands

Animal coordination, control and homeostasis is built around the idea of keeping the internal environment steady, mostly by hormones and negative feedback. The examiners test the endocrine glands and their hormones, the menstrual cycle and its four hormones, the control of blood glucose and diabetes (with BMI), and (Biology only) thermoregulation and the kidney. This guide ties together the four dot-point pages, each with its own practice questions.

Hormones, adrenalin and thyroxine

The endocrine system releases hormones into the blood, which carry them to target organs, giving slower but longer-lasting and more widespread effects than nerves. Adrenalin, from the adrenal glands, prepares the body for fight or flight (raising heart rate, blood pressure, blood flow to muscles and blood glucose). Thyroxine, from the thyroid, controls metabolic rate and is kept steady by negative feedback through TRH and TSH.

The menstrual cycle, contraception and fertility

Four hormones control the menstrual cycle: FSH matures the egg and triggers oestrogen, which builds the lining and triggers LH; LH causes ovulation; and progesterone maintains the lining. Hormonal contraception inhibits FSH; barrier methods stop sperm and protect against STIs. In assisted reproduction, FSH and LH (or clomifene) stimulate ovulation, and IVF fertilises eggs outside the body.

Blood glucose, diabetes and the kidney

The pancreas controls blood glucose with insulin (lowers it, storing glycogen) and glucagon (raises it). Type 1 diabetes lacks insulin (injections); type 2 has insulin resistance (diet and exercise), linked to a high BMI. (Biology only) Thermoregulation by the skin uses sweating and vasodilation to cool, and vasoconstriction and shivering to warm. The kidney filters blood in nephrons, reabsorbs useful substances, and uses ADH for osmoregulation.

How Topic 7 is examined

• Negative-feedback loops. Explaining the control of thyroxine, blood glucose, temperature and water.
• Calculations. BMI (mass over height squared) and waist-to-hip ratios.
• The menstrual cycle. The roles of FSH, LH, oestrogen and progesterone.
• Application. Predicting urine concentration on a hot day, and choosing contraception for a need.

Check your knowledge

A mix of recall and calculation questions covering Topic 7. Attempt them under timed conditions, then check against the solutions.

1. State the gland that releases adrenalin and one effect of adrenalin. (2 marks)
2. Define negative feedback. (1 mark)
3. State the hormone that causes ovulation and where it is made. (2 marks)
4. Give one advantage of a condom over the contraceptive pill. (1 mark)
5. State which hormone lowers blood glucose and where it is made. (2 marks)
6. Give one difference between the causes of type 1 and type 2 diabetes. (1 mark)
7. A person has a mass of $96\ kg$ and a height of $1.6\ m$. Calculate their BMI. (2 marks)
8. State what happens to the skin blood vessels when the body is too cold, and name the process. (2 marks)