Homeostasis and Feedback
- Biology
- Ages 14–18 · Grades 9–12
What you’ll find out
- Homeostasis keeps internal conditions within narrow limits so enzymes and cells can work.
- Negative feedback loops use receptors, a control centre and effectors to reverse changes.
- Insulin and glucagon control blood glucose antagonistically; diabetes results when this fails.
No sign-up and no real names. In the lesson you check your understanding as you read, and practise until it sticks.
Keeping conditions steady
Cells work properly only within narrow limits of temperature, water and chemical levels, so the body keeps its internal environment steady, a process called homeostasis. Human body temperature, for example, stays close to 37 degrees Celsius. Most homeostasis works by negative feedback. Sensors detect a change, a control centre such as the brain compares it with the normal value, and effectors bring about a response that reverses the change. If you overheat, you sweat and blood vessels near the skin widen to lose heat; if you get cold, you shiver and those vessels narrow to keep heat in.
Blood glucose and hormones
Blood carries glucose to every cell as fuel, and its concentration must stay within a narrow range. After a meal, blood glucose rises. Cells in the pancreas detect this and release the hormone insulin into the blood. Insulin causes liver and muscle cells to take up glucose and store it as glycogen, so blood glucose falls back towards normal. If blood glucose falls too low, the pancreas releases a second hormone, glucagon, which makes the liver break down glycogen and release glucose. In diabetes, this system fails, either because the pancreas makes too little insulin or because cells stop responding to it.
Curriculum links: NGSS HS-LS1-3 · England KS4: Biology · Cambridge IGCSE: Biology · NCERT Science, Class 10