natural

Unit1

Interaction, a life process

Living things interact with each other and the world around them in many ways.

For example, these fish are interacting with the shark. They help it to keepclean by eating parasites.

In order to interact with other living things and with our surroundings, we need to receive information about them. We use our senses to get this information.

Which organs make up the nervous system?

The brainIt receives information and then sends a message toa part of the bodyto tell it how to react.

The spinal cordIt connects the brain to the rest of the body.

Nerves They connect the spinal cordto our muscles, joints and skin.

Motor nerves transmit messages our brain sends to the muscles, joints and skin.

Sensory nerves receive messages from the muscles, joints and skin and send them to the brain.

It is made up of the cerebrum, the cerebellumand the brainstem.

How does the nervous system work?

The nervous system is made up of millions of neurons, which receive and transmit messages from different parts of the body and from the brain.

Neurons are star-shaped. They consist of a cell body, a long extension called the axonand shorter, thin fibres called dendrites.

To transmit messages, they create nerve impulses(electrical signals).Cell body: It controls the neuron. Creates impulses.Axon: It transmits the impulses to other neurons.Dendrites: They receive nerve impulses from other neurons.

How do we see?

The iris is made of small muscles. It opens and closes the pupil.

The pupil is a small hole that lets light into the eye.

The cornea covers and protects the iris and the pupil.

The lens is a transparent, oval-shaped structure that focuses light onto the retina. It’s located behind the pupil and the iris.

The retina is made of nervous tissue arranged in thin layersof cells that detect light and colours. They send information to the optic nerve.

The optic nerve is connected to the brain. It transmitsinformation from the retina.

How do we hear?

Sound waves go into our ear and hit the eardrum. As a result, the eardrum vibrates.

When the eardrum vibrates, it makes the small bones inside the ear vibrate, too.

The cochlea detects the vibrations and produces nerve impulses. The auditory nerve transmits these impulses to the brain. Then the brain interprets the information.

How do we taste and smell?

Smells are made up of gases in the air. When air goes into your nose, the gases go into your nasal passages. The olfactory cells detect the gases and send nerve impulses to the olfactory nerve. It transmits the impulses to the brain and the brain interprets the information.

The tiny, pink bumps on your tongue are called tastebuds. They can detect special chemicals in the things that you eat and drink. The chemicals mix with saliva and then the tastebuds detect them. The tastebuds produce nerve impulses and transmit them to the gustatory nerves. These nerves then transmit the impulses to the brain, which interprets the information.

How can we keep our nervous system healthy?

You should look after your brain and your muscles, because the nervous system is responsible for movement, breathing and your heartbeat.

Keeping your brain healthy

• You should exercise it for example by doing puzzles or playing thinking games.

• You can also train your memory and solve mathematical or linguistic problems. I

• t’s also important to rest your brain. Have enough hours of sleep.

• A balanced diet is also important for a healthy brain.

• You should also drink lots of water.

Keeping your muscles healthy

• Do regular exercise. This guarantees a regular supply of blood and oxygen to your muscles.

• By doing exercise, you’re also exercising your heart and lungs.