Balance Basics
How your body holds its inside world steady: homeostasis, the receptor–coordination centre–effector pathway, and negative feedback.
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Balance Basics ⚖️
The world outside you swings wildly — hot, cold, hungry, thirsty — yet inside, your body holds conditions remarkably **steady**. That balancing act is **homeostasis**. Learn what it keeps constant, the machinery that does it, and the feedback trick that keeps everything on target.
A steady inside world 🌡️
**Homeostasis** is the regulation of the **internal environment** to keep conditions **constant**, in response to internal and external changes. In the body, three things are controlled: **blood glucose concentration**, **body temperature** and **water levels**.
Why keep it constant?
Why must the body keep its internal conditions constant?
- So cells and their enzymes work at their optimum
- So the body can keep growing taller
- To store more energy as fat
- To make the heart beat faster
The control system 🎛️
Every automatic control system has three parts, each with a precise job: • **Receptors** — cells that **detect** a change (a stimulus). • **Coordination centres** — e.g. the **brain**, spinal cord or **pancreas** — receive and **process** the information. • **Effectors** — **muscles or glands** — bring about a **response** to put things right.
Trace the pathway
An interactive activity.
Match the role
- Receptor
- Coordination centre
- Effector
- Detects a change (a stimulus)
- Receives and processes the information
- A muscle or gland that brings about a response
Name the part
The pancreas receives information about blood glucose and processes it. Which control-system component is the pancreas acting as?
- A coordination centre
- A receptor
- An effector
- A stimulus
The feedback trick ↩️
How does the body know when to stop correcting? **Negative feedback**. When a level moves **away** from its normal set point, the control system triggers a response that pushes it **back** — too high is brought down, too low is brought up. The correction stops once normal is restored.
Name the parts
A control system has three parts: a _____ detects the change, a _____ centre processes it, and an _____ brings about the response.
How feedback works
In negative feedback, what happens when body temperature rises **above** normal?
- The control system triggers a response that lowers it back to normal
- The system pushes the temperature even higher
- Nothing happens until it becomes dangerous
- All body processes stop
In the exam 🎓
Balanced. Grade-9 habits for homeostasis: • **Homeostasis** = keeping the internal environment constant (blood glucose, temperature, water) so cells and enzymes work. • Name each part's role **precisely**: receptors **detect**, coordination centres **process**, effectors (muscles/glands) **respond**. • **Negative feedback** reverses any change back towards the normal set point.