Temperature Control
Overview
Walk out of an air-conditioned room into a hot street and almost nothing about you changes. Your skin flushes, you start to feel damp, and within a few minutes you are uncomfortable. What has not changed is the number that matters: the temperature deep inside your chest and skull, which your body defends near 37 °C whether the air outside is at 5 °C or 40 °C. Enzymes are the reason. Let the core drift a few degrees either way and the reactions that keep you alive slow down or stop entirely.
This lesson follows the control system that does the defending, and it is one of the few biology topics on this course where the two tiers genuinely part company. You will find out where in the brain the decision is made and what two separate sets of receptors it listens to, both of which every candidate needs. You will then go on to the detail the specification prints in bold: what really widens when someone says a person's blood vessels have dilated, why a layer of sweat only cools you once it evaporates, and why a shivering muscle is warming you with a chemical reaction you already know by name.
Objectives
- Body temperature is monitored and controlled by the thermoregulatory centre in the brain. The thermoregulatory centre has receptors sensitive to the temperature of the blood flowing through the brain. The name of the centre in the brain (hypothalamus) is not required.
- Temperature receptors in the skin send impulses to the thermoregulatory centre, giving information about skin temperature.
- If the core body temperature is too high: blood vessels supplying the skin capillaries dilate so that more blood flows through the capillaries and more energy is transferred from the skin to the environment; sweat glands release more sweat, which cools the body as it evaporates. Sweating helps to cool the body. More water is lost when it is hot, and more fluid has to be taken through drink or food to balance this loss. Core Tier students are not expected to describe details of changes in the blood vessels when the core body temperature is too high, but should understand that the skin looks red when we are hot due to increased blood flow.
- If the core body temperature is too low: blood vessels supplying the skin capillaries constrict to reduce the flow of blood through the capillaries; muscles may ‘shiver’ - their contraction needs respiration, which transfers energy to warm the body. Core Tier students are not expected to describe details of changes in the blood vessels when the core body temperature is too low.
Mind map
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Lesson Note
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Lesson Evaluation
Congratulations on completing the lesson on Temperature Control. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.
You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.
Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.
- What do the receptors inside the thermoregulatory centre respond to? A. The temperature of the air around the body B. The temperature of the blood flowing through the brain C. The temperature of the skin surface D. The concentration of glucose in the blood Answer: B
- The core body temperature rises above normal. Which response takes place? A. The blood vessels supplying the skin capillaries constrict B. The sweat glands release less sweat C. The blood vessels supplying the skin capillaries dilate D. The skeletal muscles begin to shiver Answer: C
- Sweat cools the body when it A. is produced by the sweat glands B. runs off the surface of the skin C. evaporates from the surface of the skin D. is wiped away with a towel Answer: C
- How does shivering help to raise body temperature? A. Friction between the moving limbs produces heat B. Muscle contraction needs respiration, which transfers energy that warms the body C. It increases the flow of blood through the skin capillaries D. It reduces the amount of sweat produced by the sweat glands Answer: B
- The specification says Core Tier students should understand why the skin looks red when we are hot. What is the reason it gives? A. The skin capillaries widen so they can be seen more easily B. Sweat on the surface makes the skin appear darker C. The flow of blood through the skin has increased D. The skin capillaries move closer to the surface Answer: C
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Work through these questions in the app
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