Balance Basics

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

Four terms carry §4.5.1, and the marks come from using them precisely.

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 has one job, and the marks go to answers that do not let a part do somebody else's.

Trace the pathway

Put the stages of a control system in the order they happen.

• A receptor detects the change
• The coordination centre processes the information
• An effector brings about a response
• The level returns to normal

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

Name the parts

A control system has three parts. A _____ detects the change, a _____ centre processes it, and an _____ brings about the response. Because that response reverses the change instead of adding to it, this is called _____ feedback.

Mark the answer

A student wrote this about getting too hot. Tap the TWO phrases that give a component the wrong job.

• When you get too hot,
• temperature receptors in the skin detect the change
• , and
• the receptors decide that you need to sweat
• . The information travels to the brain,
• which processes it and works out the response
• . Then
• the sweat glands choose how much sweat to release

Run the correction

You step outside on a cold day and your body temperature starts to fall below its set point. Work through the control system that puts it right.

• What detects that your body temperature has fallen?
• That information reaches the coordination centre. What is its job?
• The response is carried out by effectors. Which are the effectors?
• Temperature is back to normal. What does negative feedback do now?

Explain it

Explain how a control system keeps body temperature steady when you get too hot, in about 50 words. Name each part and give it the right job:

• what detects the change, and what it does not do
• what processes the information and decides on the response
• what actually carries that response out
• why the whole thing is called negative feedback

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.