Principles of homeostasis and negative feedbackAQA A-Level Biology: Mind map

Exam questions on Principles of homeostasis and negative feedback

1. In a healthy human, core temperature is held at about 37 °C and blood pH at about 7.4. Both stay within very narrow limits, even though the environment and the person's activity change from hour to hour.
   Explain what is meant by negative feedback.2 marks
2. Hormone X is secreted by an endocrine gland into the blood. It circulates to every organ in the body, but only liver cells show a response to it. The response begins within minutes and lasts for several hours.
   Explain why a response to a hormone is usually slower than a response to a nerve impulse.2 marks
3. During childbirth, the baby's head stretches the cervix. Stretch receptors send impulses to the hypothalamus, which causes oxytocin to be released from the posterior pituitary gland into the blood. Oxytocin stimulates the muscle of the uterus to contract more strongly, which pushes the baby's head harder against the cervix.
   Explain why this is an example of positive feedback.3 marks