AQA GCSE Combined Science (8464), Higher tier · Biology › Homeostasis and response › Hormonal coordination in humans
Practise Feedback systems (HT only). 11 exam-style questions on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
How adrenaline prepares the body for 'fight or flight', how thyroxine controls metabolic rate, and how negative feedback keeps thyroxine levels steady. This is Higher tier content: expect short explanations and questions that ask you to interpret a simple feedback diagram.
Grade by grade
What you need to be able to do, from the first marks up to the top grade.
5
State the effects of adrenalineIt increases heart rate and boosts delivery of oxygen and glucose to the brain and muscles.
5
State the role of thyroxineIt stimulates the basal metabolic rate and is important in growth and development.
6
Define negative feedbackA change away from normal triggers a response that reverses the change, returning the level to normal.
7
Explain how thyroxine levels are controlledHigh thyroxine inhibits TSH release from the pituitary, so less thyroxine is released, and the reverse.
8
Interpret simple negative feedback diagramsFollow the arrows to predict and explain what happens when a hormone level rises or falls.
Notes
Adrenaline
Adrenaline is produced by the adrenal glands in times of fear or stress.
It increases the heart rate and boosts the delivery of oxygen and glucose to the brain and muscles.
This prepares the body for 'fight or flight': the muscles can respire faster, releasing more energy for action.
Thyroxine
Thyroxine is produced by the thyroid gland in the neck.
It stimulates the basal metabolic rate: the rate of the chemical reactions in your body when you are at rest.
It plays an important role in growth and development.
Thyroxine levels are controlled by negative feedback.
Negative feedback
In negative feedback, a change away from the normal level triggers a response that reverses the change, bringing the level back to normal.
The pituitary gland releases TSH (thyroid stimulating hormone), which stimulates the thyroid to release thyroxine.
If thyroxine rises above normal, TSH release is inhibited, so the thyroid releases less thyroxine and the level falls.
If thyroxine falls below normal, more TSH is released, so the thyroid releases more thyroxine and the level rises.
Insulin and glucagon controlling blood glucose is another example of negative feedback.
Cheatsheet
Adrenaline: adrenal glands; released in fear or stress; 'fight or flight'
Adrenaline: increases heart rate; more oxygen and glucose to the brain and muscles
Thyroxine: thyroid gland; stimulates basal metabolic rate; growth and development
Negative feedback: a change triggers a response that reverses it
Pituitary → TSH → thyroid → thyroxine
Thyroxine too high → less TSH → less thyroxine (and the reverse)
How to answer each type of question
Explain the effects of adrenaline
3 to 4 marks6
Name the hormone and the gland if asked.
Link the chain: heart rate → blood flow → oxygen and glucose → respiration in muscles → energy for action.
Example. A student is frightened by a loud bang, and her heart starts to beat faster. (a) Name the hormone that causes this response. (b) Explain how a faster heart rate helps her body respond to danger.
Show the model answer
(a) Adrenaline (1) (b) More blood is pumped to the brain and muscles (1), delivering more oxygen and glucose (1), so the muscles can respire faster, releasing energy for 'fight or flight' (1)
Explain how thyroxine is controlled by negative feedback
3 to 4 marks7
Start with the change: thyroxine too high or too low.
Say what happens to TSH release from the pituitary gland.
Say what the thyroid does, and that the level returns to normal.
Example. A person's blood thyroxine concentration rises above normal. Explain how negative feedback returns it to normal.
Show the model answer
The high thyroxine concentration inhibits the release of TSH from the pituitary gland (1). Less TSH reaches the thyroid gland (1), so the thyroid releases less thyroxine (1), and the thyroxine concentration falls back to normal (1).
Interpret a negative feedback diagram
2 to 4 marks8
Follow each arrow and note whether it means 'stimulates' or 'inhibits'.
Work out what happens when one part stops working.
Link the hormone level to its effect on the body.
Example. A diagram shows: pituitary gland → TSH → thyroid gland → thyroxine → body cells. An arrow labelled 'inhibits' goes from thyroxine back to the pituitary gland. (a) A person's thyroid gland cannot make thyroxine. Predict what happens to their TSH level. Give a reason. (b) Suggest how their basal metabolic rate is affected. Give a reason.
Show the model answer
(a) The TSH level increases / stays high (1), because there is no thyroxine to inhibit the pituitary gland (1) (b) Their basal metabolic rate is lower than normal (1), because there is no thyroxine to stimulate it (1)
Shortcuts and memory tricks
Negative feedback = 'do the opposite': if it goes up, bring it down; if it goes down, bring it up.
TSH = Thyroid Stimulating Hormone: its name tells you what it does.
Think of a thermostat: when the room is warm enough, the heating switches off.
Adrenaline = alarm hormone: fast and short-term. Thyroxine = steady, long-term control of metabolism.
Where marks are lost
Thinking 'negative' means harmful. Negative feedback means the response reverses the change.
Mixing up adrenaline (fight or flight) and thyroxine (metabolic rate, growth and development).
Putting the thyroid in the brain. The thyroid is in the neck; the pituitary is in the brain.
Saying adrenaline 'gives you energy'. It increases the delivery of oxygen and glucose so muscles can respire faster.
Stopping before the end: say that the level returns to normal.
Exam technique
In feedback questions, use 'inhibits' and 'stimulates' and follow the diagram one step at a time.
Always finish a negative feedback explanation with 'so the level returns to normal'.
For adrenaline, link heart rate → blood flow → oxygen and glucose → respiration in muscles.
Quick recall
Cover the answers and test yourself. The app has these as flashcards that come back just before you'd forget them.
Adrenaline and thyroxine are two hormones. Name the gland that produces thyroxine.
Thyroid gland
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy5 marks
Adrenaline and thyroxine are two hormones.
(a) Which gland produces adrenaline? Tick (✓) one box.[1]
Adrenal gland
Pancreas
Pituitary gland
Thyroid gland
(b) Adrenaline is released in times of fear or stress. Give two effects of adrenaline on the body.[2]
(c) Name the gland that produces thyroxine.[1]
(d) Thyroxine stimulates the basal metabolic rate. Give one other role of thyroxine in the body.[1]
Show the answer and mark scheme
(a)Answer: Adrenal gland
(b)Answer: It increases the heart rate and boosts the delivery of oxygen and glucose to the brain and muscles
increases heart rate
increases the delivery of oxygen / glucose to the brain / muscles
(c)Answer: Thyroid gland
thyroid (gland)
(d)Answer: It is important in growth and development
growth / development
Question 2Medium5 marks
Cortisol is a hormone released by the adrenal glands when a person is under stress. Its release is controlled like this: • the pituitary gland releases a hormone called ACTH • ACTH stimulates the adrenal glands to release cortisol • a high concentration of cortisol in the blood causes the pituitary gland to release less ACTH.
(a) Describe what happens to the release of ACTH and cortisol if the concentration of cortisol in the blood falls below normal.[2]
(b) Which statement describes negative feedback? Tick (✓) one box.[1]
A change in a level causes a response that makes the change bigger
A change in a level causes a response that reverses the change
A level is kept constant by the nervous system only
Hormones are released only when a person is under stress
(c) Some people take tablets containing a drug that acts like cortisol for a long time. Suggest what happens to the amount of cortisol made by their own adrenal glands. Explain your answer.[2]
Show the answer and mark scheme
(a)Answer: The pituitary gland releases more ACTH, which stimulates the adrenal glands to release more cortisol, so the cortisol concentration rises back towards normal
the pituitary gland releases more ACTH
so the adrenal glands are stimulated to release more cortisol, and the cortisol concentration rises back towards normal
(b)Answer: A change in a level causes a response that reverses the change
(c)Answer: The drug acts like a high concentration of cortisol, so the pituitary gland releases less ACTH; the adrenal glands are stimulated less and make less of their own cortisol
the drug acts like a high cortisol concentration, so the pituitary gland releases less ACTH
so the adrenal glands are stimulated less and make less of their own cortisol
Question 3Hard8 marks
The thyroid gland needs iodine from the diet to make thyroxine. The pituitary gland releases TSH, which stimulates the thyroid gland to release thyroxine. TSH also stimulates the cells of the thyroid gland to grow and divide.
(a) People whose diet contains too little iodine often develop a swelling of the thyroid gland in the neck, called a goitre. Use the information to explain why.[3]
(b) Children who do not get enough iodine may grow more slowly. Suggest why.[2]
(c) In one region, 32% of 2500 children had a goitre. Salt with added iodine was then introduced. Five years later, 6% of 2800 children in the region had a goitre. Calculate the decrease in the number of children with a goitre.[3]
Show the answer and mark scheme
(a)Answer: Too little thyroxine is made; the low thyroxine concentration no longer inhibits the pituitary gland, so it releases more TSH; TSH stimulates the thyroid gland to grow
less thyroxine is made (without iodine)
low thyroxine concentration causes the pituitary gland to release more TSH / less inhibition of TSH release
(more) TSH stimulates the thyroid gland to grow (and swell)
(b)Answer: They make less thyroxine, and thyroxine plays an important role in growth and development
less thyroxine is produced
thyroxine is needed for (normal) growth and development / to stimulate metabolic rate