Homeostasis, feedback and thermoregulationEdexcel A-Level Biology A: Mind map

Exam questions on Homeostasis, feedback and thermoregulation

1. A runner begins a 10 km race on a warm, humid morning. As her muscles respire faster, they release large amounts of heat and her core body temperature starts to rise above its normal value of about 37 °C.
   Explain how sweating helps to lower the runner's body temperature.2 marks
2. Physiologists compare two types of control system in the human body. In one, a rise in core temperature triggers responses that bring the temperature back down. In the other, during childbirth, stretching of the cervix stimulates the release of the hormone oxytocin, which strengthens uterine contractions, which in turn stretch the cervix further.
   Explain why positive feedback cannot be used to keep body temperature stable.2 marks
3. A runner is monitored during 60 minutes of steady running. Her core temperature rises from 37.0 °C to 38.4 °C over the first 25 minutes and then stays at 38.4 °C for the rest of the run. Over the same period the blood flow through her skin increases from 0.30 dm³ min⁻¹ at rest to 2.40 dm³ min⁻¹.
   Calculate the percentage increase in the blood flow through the runner's skin between rest and the end of the run.3 marks