الأسبوع 4 · المحور الأول، الوحدة الأولى، المفهوم 1.2 «كيف تعمل الحواس؟» (أ): الحواس والجهاز العصبي · 3 دروس
3
Smell, nerves and the brain
Discovery Education Science P4: Term 1, Unit 1, pp. 34–46
GoalFollow a message from a sense organ along the nerves to the brain and say what the brain does with it.
New words
receptor · a tiny part of a sense organ that reacts to light, sound, smell or touchnerve · a long thread that carries messages between the body and the brainbrain · the part that makes sense of messages and decides what to do
Explanation
Each sense organ has tiny receptors. A receptor reacts to something in the world and starts a message. The message travels along nerves, which are like wires, to the brain. The brain works out what the message means and decides what to do. For example, the smell of fresh bread reaches receptors in your nose. A message goes along a nerve to your brain. Your brain says “bread” and “I feel hungry”, and you ask your dad to buy some. Or your bare feet touch a cold tile. Receptors in your skin send a message, your brain works out “cold”, and you go to find slippers. The whole journey happens in a blink. Without the brain, the messages would not mean anything.
receptors in the nose→nerve→brain→decision
Worked examples
Jana smells bread from the bakery. Her nose, a nerve and her brain work together. Her brain says “bread”, and she decides to ask for some.
Farida steps on a cold floor. Receptors in her foot send a message along a nerve. Her brain works out that it is cold, and she puts on warm socks.
Imagine the nerves from the eye could not carry messages. The eyes could still collect light, but the message could not reach the brain, so nothing would be seen. The nerve is the road for the message.
Class activity
Message chain game. Stand in a line of five children. The first child gets a short secret message from a grown-up, such as a picture to draw. Pass it by whispering to the next child; the last child tells the brain (the grown-up). Compare the first and last messages. Talk about why a nerve must carry the message clearly.
Practice
1
What do receptors do?
They react to things like light, sound, smell or touch and start a message.
2
What carries the message from the nose to the brain?
A nerve.
3
Put in order: brain decides, receptors react, nerve carries the message.
Receptors react, a nerve carries the message, the brain decides.
4
Karim touches something cold. Which sense organ gives the information, and where is it processed?
