Worked Example: A Science Interview

In this lesson we'll work through one complete science interview, question by question: a five-question sequence on how the body controls its temperature, and what changes in a fever. For each question we show how to approach it, where candidates usually go wrong, and what a strong answer does.

Try each question out loud before reading on.

Question 1: "How does the body keep its temperature steady?"

How to approach it: This is GCSE and A-level content, so give all of it, in an organised way: what detects a change, what compares it, and what responds, for both too hot and too cold.

Where candidates go wrong: Listing responses ("sweating, shivering, hairs standing up") with no sense of how they are controlled. Or saying that blood vessels move closer to the skin. They don't move: the arterioles supplying the skin widen or narrow. If the tutor asks "how does the body know what temperature it should be?", they are asking for the comparison with a set point.

A strong answer:

It's negative feedback. Temperature receptors in the skin and in the hypothalamus detect changes, and the hypothalamus compares the core temperature with a set point of about 37°C. If the body is too hot, it increases heat loss: sweat evaporates from the skin and takes heat with it, and the arterioles supplying the skin widen, so more warm blood flows near the surface and loses heat. If it's too cold, the opposite happens: the skin arterioles narrow to keep heat in the core, and the muscles shiver, which releases heat from respiration. Whatever the change, the response opposes it and brings the temperature back towards the set point.

Why it works: It is organised into detect, compare and respond, and it names the set point. That detail seems minor here, and it turns out to be what the rest of the interview depends on.

Question 2: "When people have a fever, they often shiver and feel cold, even though their temperature is already high. Why?"

How to approach it: Start from your answer to Question 1. Shivering is a response to being too cold, so ask: too cold compared with what?

Where candidates go wrong: Saying the body has lost control of its temperature, or that shivering somehow cools it down. Both ignore what was said in Question 1. If the tutor asks "what is the hypothalamus comparing the temperature with?", they are pointing you to the set point.

A strong answer:

So the puzzle is why someone who is already hot responds as if they were cold. I think the answer is in what the body compares its temperature with. Shivering and narrowing the skin's blood vessels are what happens when the core temperature is below the set point. So if those responses are happening at a high temperature, the set point itself must have gone up, perhaps to 39°C. At 37°C the body is now too cold compared with its new target, so it shivers and holds on to heat until it gets there. That would also explain why the person feels cold and looks pale while their temperature is rising.

Why it works: It restates the puzzle and says how it will approach it before starting, as described in Lesson 4. Then it reasons from the mechanism in Question 1 rather than searching for a remembered fact. The control system is working normally, and only its target has changed.

The tutor may add that the set point is raised by chemical signals released by the immune system during an infection. That is beyond A-level, and you aren't expected to know it. What matters is that you can use it once you are told.

Question 3: "What would you expect to happen when the fever breaks?"

How to approach it: Go in three steps: what normally happens, what has changed, and what follows. Here the set point drops back to normal while the body is still hot.

Where candidates go wrong: Saying the temperature simply drifts back down, or predicting more shivering. If the tutor asks "where is the set point now, compared with the body's temperature?", they are asking you to run the comparison again.

A strong answer:

If the set point falls back to 37°C while the body is still at 39°C, the body is now too hot compared with its target. So the heat-loss responses switch on. The person sweats, and the skin's blood vessels widen, so they look flushed and feel hot, and they might throw off the covers, even though their temperature is falling. That fits with people waking up drenched in sweat when a fever breaks.

Why it works: It runs the same comparison as Question 2 in the other direction, states what the patient would notice, and ends with a prediction that can be checked against experience.

Question 4: "Paracetamol brings a fever down by acting on the brain. It doesn't kill the virus or bacteria. So what is it actually doing, and would you expect it to make the infection clear up faster?"

How to approach it: The tutor has added a new fact. Combine it with your model of the set point.

Where candidates go wrong: Saying that paracetamol fights the infection, or that it cools the body directly. "Acting on the brain" and "doesn't kill the virus" are both hints.

A strong answer:

If it acts on the brain and brings the temperature down, the most likely explanation is that it lowers the set point, so the body loses heat in the same way as when a fever breaks. But it does nothing to the cause. The infection is still there and the immune system still has to clear it, so I wouldn't expect it to clear up any faster. It treats the symptom, not the disease. If the fever is doing something useful, bringing it down might even slow recovery slightly, though I don't know whether that's true.

Why it works: It uses both parts of the new fact, separates the symptom from the cause, and is open about what it doesn't know. That last point is exactly where the tutor will go next.

The tutor may then try a different case: someone who collapses with heatstroke after running a marathon on a hot day. Would paracetamol help? The reasoning is the same. In heatstroke the set point is normal, and the body is simply gaining heat faster than it can lose it. Paracetamol lowers a raised set point, so it would do little here, and the patient needs to be cooled directly. A candidate who has understood Question 4 can answer this straight away.

Question 5: "If a fever is the body's own response, should we always try to bring it down?"

How to approach it: There is no single right answer, so build your view from the science. Weigh the possible benefits against the costs, then say what the decision depends on.

Where candidates go wrong: A flat yes or no. "Yes, because fever is harmful" ignores why the body might raise its temperature on purpose. "No, because it's natural" ignores the costs. If the tutor asks "why might the body raise its temperature deliberately?", they want the possible benefits first.

A strong answer:

Not always. A response that costs this much energy has probably survived because it helps. Many pathogens grow best at normal body temperature, so a higher temperature may slow them down, and immune reactions depend on enzymes, so some may speed up as the temperature rises. But there are costs. A higher temperature means a higher metabolic rate, so the body needs more oxygen and energy, and sweating loses water. That might matter little to a healthy adult, but a lot to someone with heart or lung disease who may struggle to meet the extra demand. And if the temperature gets very high, proteins start to denature. So it depends on how high the fever is, how unwell and uncomfortable the patient is, and what other conditions they have. If I wanted to know whether bringing a fever down helps or harms recovery, I'd want a trial that randomly allocates patients to treatment or no treatment and compares how quickly they recover.

Why it works: It gives the benefits before the costs, takes each one from A-level science (enzymes, metabolism, protein structure), fits the conclusion to the patient, and ends with how the question could be settled with evidence, using the study design in Lesson 3.

In practice, UK guidance for children with a fever is to consider paracetamol or ibuprofen if the child is distressed, not simply to bring the temperature down. You wouldn't be expected to know that, but if the tutor tells you, it should fit the reasoning above.

• Only one of the five questions was recall. The other four were answered by reasoning from the first answer.
• One idea carried the whole interview. Once fever was seen as a raised set point, the shivering, the sweating when it breaks, what paracetamol does and why it fails in heatstroke all followed. This is why negative feedback is one of the common themes in Lesson 3.
• The first answer was needed for the rest. Naming the set point in Question 1 is what made Question 2 answerable. A list of responses with no comparison would have left nothing to reason from.
• New facts were there to be used. "Acting on the brain" and "doesn't kill the virus" contained most of the answer to Question 4.
• The science led to a decision. Question 5 had no single right answer. It tested whether the candidate could weigh costs and benefits from the science and fit the conclusion to the patient.