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Biological ScienceLife ProcessesYear 2 Science

Breathing, moving and sensing

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What this lesson covers

  • Muscles move your body by pulling
  • A muscle gets shorter to pull, then relaxes
  • Breathing in: muscles lift your ribs out and air comes in
  • Breathing out: the muscles relax, your ribs move in and air goes out
  • Your sense organs pick up light, sound, smells, touch and heat, and your brain works out what they mean
  • Testing what each sense organ can pick up
Key idea

Muscles pull

  • Muscles are the parts of your body that make it move.
  • A muscle can only pull. To pull, it gets shorter and fatter. This is called contracting.
  • When a muscle stops pulling, it relaxes and gets longer again.
  • Muscles are joined to bones, so when a muscle pulls, a bone moves.
A bent arm: the upper arm bone and lower arm bone meet at the elbow, and the muscle on the front of the upper arm is short and fat, pulling the lower arm up
Worked example

Bend your arm

  • Hold your left hand on the front of your right upper arm. Slowly bend your right elbow, then straighten it. What do the muscles do?
  1. Bending: the front muscle gets shorter and harderit contracts
  2. It pulls the lower arm upa muscle pulls a bone
  3. Straightening: the front muscle relaxes, and a muscle at the back pulls insteadmuscles cannot push
  4. One muscle pulls to bend the arm; another pulls to straighten it
Key idea

How you breathe

  • Your lungs are inside your chest, behind your ribs.
  • To breathe in, muscles contract and lift your ribs up and out. Your chest gets bigger, and air rushes in through your nose or mouth.
  • To breathe out, the muscles relax. Your ribs drop back in, your chest gets smaller, and air is pushed out.
  • Put your hands on your ribs and take a deep breath. Feel them move out, then in.
Two chests: breathing in, the ribs move outward and air comes in through the nose; breathing out, the ribs move back in and air goes out
Key idea

Try it: breathing in or out?

Key idea

Your senses

  • Your senses tell your brain what is around you.
  • Each sense organ picks up something different and sends a message to your brain.
  • Your brain works out what the message means: bright, loud, smelly, hot or soft.
Sense organSenseIt picks up
EyesSightLight and colour
EarsHearingSound
NoseSmellStrong and faint smells
TongueTasteSweet, salty, sour and bitter
SkinTouchLight and hard touch, hot and cold
The brain in the middle, with arrows coming in from the eyes (light), the ears (sound), the nose (smell) and the skin (touch and heat)
Key idea

Try it: which sense organ?

Worked example

Strong and faint smells

  • Room 9 put 1 drop of vanilla on one cotton ball and 5 drops on another. Ten children each sniffed both from an arm's length away.
Cotton ballChildren who smelled it
1 drop2 of 10
5 drops9 of 10
  1. 1 drop: 2 of 10 children smelled ita faint smell
  2. 5 drops: 9 of 10 children smelled ita strong smell
  3. A stronger smell is easier for the nose to pick up, but people's noses differ
Key idea

Try it: who smelled the vanilla?

Key idea

Touch, hot and cold

  • Your skin can feel a light touch, like a feather, and a hard press, like a push.
  • It can also feel hot and cold.
  • Your fingertips and lips feel touch better than your back does.

Common mistakes

  • Muscles push bones to move them.
    Muscles can only pull; to move a bone back, another muscle pulls the other way.
  • When I breathe in, the air goes into my stomach.
    Air goes down into your lungs; your tummy moves because the muscles under your lungs move.
  • My eyes do all the seeing by themselves.
    Your eyes pick up light, but your brain works out what you are looking at.
Try it at home

The three bowls test

You need: 3 bowls, cold tap water, warm tap water, a clock or timer

  1. Fill one bowl with cold tap water, one with warm tap water, and the middle bowl with a mix of the two.
  2. Put one hand in the cold bowl and the other hand in the warm bowl.
  3. Keep them there while you count slowly to 60.
  4. Now put both hands into the middle bowl together.
  5. Look for this: the same water feels warm to one hand and cool to the other, because your skin compares it with what it felt before.

Safety: Ask an adult to run the warm water and test it with their own hand first, so it is warm and not hot enough to scald.

Your turn

1

When a muscle contracts, does it get shorter or longer?

2

When you breathe in, do your ribs move in or out?

3

Which sense organ picks up a smell?

4

Which part of your body works out what your senses pick up?

5

In Room 9's test, how many children smelled the 5-drop cotton ball?

Show answer

1. Shorter, and fatter. 2. Out. 3. The nose. 4. The brain. 5. 9 of 10 children.

Summary

Recap

  • Muscles pull on bones to move them; they contract to pull and relax to stop.
  • Breathing in, muscles lift your ribs out and air comes into your lungs.
  • Breathing out, the muscles relax, your ribs move in and air goes out.
  • Eyes, ears, nose, tongue and skin pick up what is around you.
  • Your brain works out what your senses are telling it.
Maths

The maths behind it

Year 2 MathsCollecting Data and Making Tally Charts
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