GCSE Biology: Temperature, Water Balance and Fertility Treatment

Homeostasis is more than blood glucose. This material covers the other control systems in the GCSE Biology homeostasis and response topic: body temperature, water balance and the kidneys, the hormones thyroxine and adrenaline, and the use of hormones to treat infertility. It complements the hormones material in this category, which deals with blood glucose, diabetes, the menstrual cycle and contraception. Much of the content is separate Biology only, and several points are Higher tier only for many students (for example, in the AQA specification deamination, ADH, negative feedback with thyroxine and adrenaline, and fertility treatment); questions on these points say so.

It begins with the general pattern of every control system — receptors, coordination centres and effectors — and applies it to temperature. You learn where temperature is monitored (the thermoregulatory centre in the brain, which has receptors sensitive to blood temperature and receives impulses from the skin), and how vasodilation and sweating transfer energy to the environment when the body is too hot, while vasoconstriction, the end of sweating and shivering conserve and release energy when it is too cold.

The section on water balance explains why cells that gain or lose too much water by osmosis stop working efficiently, why losses from the lungs and skin cannot be controlled, and how the kidneys make urine by filtering the blood and selectively reabsorbing glucose, some ions and water. A data question asks you to read concentrations in plasma, filtrate and urine, and the written sheet includes a calculation of the percentage of filtrate reabsorbed. Higher tier points follow: deamination of excess amino acids to ammonia and then urea in the liver, and the negative feedback loop in which ADH from the pituitary gland makes the kidney tubules more permeable to water. You also compare dialysis with a kidney transplant.

The final part covers thyroxine, which stimulates the basal metabolic rate and is controlled by negative feedback, and adrenaline, which prepares the body for fight or flight; then fertility drugs containing FSH and LH, the stages of IVF, and its drawbacks and ethical questions.

Four formats are offered. The quiz has twelve questions with explanations. The flashcards cover the key terms, from thermoregulatory centre and selective reabsorption to ADH, dialysis and IVF. The printable written sheet has eight longer questions — explaining temperature responses, processing kidney data, describing the ADH feedback loop, evaluating dialysis against a transplant and discussing IVF — to complete by hand and photograph for feedback. The oral exam lets you talk the topic through with an examiner who asks one question at a time and gives brief feedback at the end.

All numerical data in the questions are illustrative.

• Describe the parts of a control system and how body temperature is monitored
• Explain how vasodilation, sweating, vasoconstriction and shivering control body temperature
• Describe how the kidneys produce urine by filtration and selective reabsorption, and interpret kidney data
• Higher: explain deamination and the negative feedback control of water balance by ADH
• Compare dialysis and kidney transplants as treatments for kidney failure
• Higher: describe the roles of thyroxine and adrenaline and evaluate fertility treatment and IVF

Practice material written by Zestly, based on the DfE GCSE biology subject content and exam-board specification content (for example, AQA GCSE Biology 8461: homeostasis; control of body temperature; maintaining water and nitrogen balance; the use of hormones to treat infertility; negative feedback). All data in the questions are illustrative.