---
title: "Quick check: feedback loops and what goes wrong"
subtitle: "Year 9 Biology · Coordination and control · Lesson 8"
---

# Quick check: feedback loops and what goes wrong

**Name:** {{field-24}} **Date:** {{field-15}} **Class:** {{field-15}}

> **Key question:** Your body keeps glucose and temperature steady all day. What happens when one part of the loop stops working?


:::teacher-note

**In one sentence:** A self-test on tracing complete negative feedback loops and locating the failure in a disorder (AC9S9U01, nodes 6 and 7, both hinge nodes taught in class).

**Students should be able to say:** I can name the parts of a feedback loop in an example. I can say the set point for body temperature and blood glucose. I can say which part of a loop fails in a disorder and what follows.

**Width:** the unmarked parts are the floor every student does (Engage, Explore, Explain, Evaluate). Typical and Wider sections add contexts, not difficulty. Students work in the online tutorial alongside this sheet.

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## Tracing a loop


:::keep-together

### Parts of the loop

**Which part of the temperature loop is it?**

Groups: Receptor, Control centre, Effector

- Temperature sensors in the skin and blood: {{field-15}}
- The hypothalamus in the brain: {{field-15}}
- Sweat glands: {{field-15}}
- Muscles that shiver: {{field-15}}
- Nerve endings that detect cold: {{field-15}}

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:::teacher-note

**Answer:** Temperature sensors in the skin and blood → Receptor; The hypothalamus in the brain → Control centre; Sweat glands → Effector; Muscles that shiver → Effector; Nerve endings that detect cold → Receptor

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:::keep-together

### Blood glucose

**Blood glucose rises after a meal. What reverses the change?**

☐ Insulin makes blood glucose rise further

☐ More glucose is released from the liver

☐ Nothing: it stays high until the next meal

☐ Insulin is released, cells take up glucose, and blood glucose falls back towards its set point

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:::teacher-note

**Answer:** Insulin is released, cells take up glucose, and blood glucose falls back towards its set point

Negative feedback: the change is detected, and the response reverses it. As glucose returns to the set point, less insulin is released.

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:::keep-together

### Set points

**Which pair names a feedback example and its set point?**

☐ Insulin, about 37 °C

☐ Body temperature, about 37 °C

☐ Sweating, about 37 °C

☐ Shivering, about 5 mmol/L

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:::teacher-note

**Answer:** Body temperature, about 37 °C

A set point is the value being held: body temperature near 37 °C, or blood glucose near 5 mmol/L. Sweating, shivering and insulin are responses.

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:::keep-together

### The whole loop

**On a hot day, match each part of the temperature loop.**

A. Corrective response

B. The return is detected

C. A change away from the set point

D. Set point

{{columns 60% 40%}}

{{rows 1}}

| Part | Letter |
|---|---|
| `Body temperature held near 37 °C` | |
| `Exercise raises body temperature to 38 °C` | |
| `Sweating and more blood flow to the skin` | |
| `The hypothalamus detects 37 °C again, so sweating slows` | |

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:::teacher-note

**Answer:** Body temperature held near 37 °C → D. Set point; Exercise raises body temperature to 38 °C → C. A change away from the set point; Sweating and more blood flow to the skin → A. Corrective response; The hypothalamus detects 37 °C again, so sweating slows → B. The return is detected

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## When the loop fails


:::keep-together

### Type 1 diabetes

**In type 1 diabetes the pancreas stops making insulin. What happens to blood glucose after a meal?**

☐ It stops being measured

☐ It falls too low

☐ It stays too high, because cells are not told to take up glucose

☐ It stays at the set point

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:::teacher-note

**Answer:** It stays too high, because cells are not told to take up glucose

The signal that triggers the response is missing, so the loop cannot bring glucose back down. Homeostasis is disrupted.

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:::keep-together

### Sweat glands

**A person's sweat glands do not work. Which part of the temperature loop has failed, and what is the consequence?**

☐ Nothing: sweating is not needed

☐ The receptor: they cannot feel heat

☐ The set point: it is lower than normal

☐ The effector: they cannot cool by sweating and can overheat in hot weather

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:::teacher-note

**Answer:** The effector: they cannot cool by sweating and can overheat in hot weather

Receptors and the control centre still work, but one effector cannot carry out the response, so the body cannot cool as well.

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:::keep-together

### Where is the fault?

**Which part of the loop has failed?**

Groups: Receptor, Control centre, Effector

- Cold sensors in the skin send no signals: {{field-15}}
- The brain does not process the signal: {{field-15}}
- Muscles do not shiver when told to: {{field-15}}

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:::teacher-note

**Answer:** Cold sensors in the skin send no signals → Receptor; The brain does not process the signal → Control centre; Muscles do not shiver when told to → Effector

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## Exit ticket

:::keep-together

**Name the parts of a negative feedback loop for body temperature.**

{{lines-3}}

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:::teacher-note

**Answer:** Receptor (skin and blood sensors), control centre (hypothalamus), effector (sweat glands, muscles, skin blood vessels), return towards 37 °C.

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