11.5 The brain and our senses

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The brain and our senses

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The role of our brainThe brain is the control centre of body activities.

Let’s see an example.

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The role of our brain1 Stimulus

The phone rings.

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The role of our brain2 Sense organ

The ears detect thesound and sendmessages to thebrain.

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The role of our brain3 Brain

The brain interprets the messages,

produces the sense of hearing and decides what to do.

The phone is ringing.

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The role of our brain4 Muscles

The brain sends messages to the muscles.

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The role of our brain5 Response

The muscles bring about a response: getting up and picking up the phone.

Hello?

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11.8The role of the brain in playing volleyball

Mandy

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11.8

Rearrange the events to describe the detection of the coming volleyball and Mandy’s response.

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11.8A Mandy’s eyes detect the light from the volleyball.

Light-sensitive cells in the eyes send messages to the brain.

B Mandy’s muscles contract/relax to enable her to jump up and pass the volleyball over the net.

C The brain sends messages to the limb muscles.

D Mandy’s brain interprets the messages. She is thinking, ‘The ball is being passed to me. Shall I

set the ball to the hitter? No, I shall pass the ball directly to the other team to try to trick them.’

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2

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11.8

The order of the events:

_____ _____ _____ _____A D BC

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The role of our brain

stimulus sense organdetected by

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The role of our brain

sense organ brain

sends messages to

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The role of our brain

brain musclesinterprets the messages and in turn sends messages to

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The role of our brain

muscles responsebring about

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The main parts of the brainprotected by the skull

brain

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Examining the human brain model11.15

human brain model

3D model

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a

b

c

cerebrum

medulla oblongata

cerebellum

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Cerebrum (大腦 )

the biggest part of the brain

Animation

responsible for intelligence

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interprets messages from sense organs

sends messages to muscles

Cerebrum (大腦 )

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the site of:

thinking

memorylearning

communication

Cerebrum (大腦 )

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one-eighth of the size of the cerebrum

Cerebellum (小腦 )

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Cerebellum (小腦 )

responsible for muscular coordination

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Cerebellum (小腦 )

maintains balance and controls movement

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the smallest part

Medulla oblongata (延腦 )

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Medulla oblongata (延腦 )

controls involuntary actions, e.g. heartbeat, breathing

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The three main parts of the brain are the cerebrum, the cerebellum and the medulla oblongata.

The main parts of the brain

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Reaction time Simulation

some react faster than others

Beep!

Why?

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Reaction timedetect a stimulus

make a response

reaction time (反應時間 )

varies from person to person

Beep!

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Measuring your reaction time11.16

1 your partner’s hand

your hand

Experiment video

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2 Catch the ruler as quickly as possible.

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3 Record the distance dropped.

1st try 2nd try 3rd try

Yourself

Distance the half-metre rule drops (cm)

Reaction time (s)

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Reaction time (s)

Distance of fall (cm)

3 Find out your reaction time from the graph.

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3

1st try 2nd try 3rd try

Yourself

Distance the half-metre rule drops (cm)

Reaction time (s)

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4 Repeat steps 1 to 3 twice.

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5 Exchange your role with your partner and repeat the activity.

1st try 2nd try 3rd try

Your partner

Distance the half-metre rule drops (cm)

Reaction time (s)

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6 What do you notice from the results of the three trials?

The more times we try, the shorter the reaction time becomes (i.e. the faster the reaction).

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7 How can we improve our reaction time?

We can improve our reaction time through training.

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Reaction time can be shortened through training

Beep!

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Reaction time affected by the condition of the

body

feeling tired

reaction time becomes longer

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Reaction time can be lengthened by

drugs and alcohol

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Reaction time is the time between detecting a stimulus and being able to make a response.

Reaction time

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It varies from person to person.

Reaction time

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Illusions

interprets messages from sense organs

incorrectly

illusions (錯覺 )

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IllusionsWhich line is a straight line, AC or BC?

BC.

A

B

C

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IllusionsHow many legs does this elephant have?

It looks like to have five legs.

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IllusionsIs the shape in red a circle?

Yes, it is a circle. 10 ¢

Put a 10 ¢ coin on it

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IllusionsClose your eyes. Feel a marble with your fingers crossed.

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IllusionsPress down on it and move it from side to side.

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IllusionsHow many marbles do you feel?

We can feel as if there are two marbles.

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Optical Illusions

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Optical Illusions

Impossible

structure

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Optical Illusions

How many

Columns?

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Optical Illusions

What do you see?

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Sometimes the brain interprets messages incorrectly.

This results in illusions.

Illusions

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1 Sense organs detect _______ and then send messages to the _______ to produce senses.

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stimulibrain

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2 After interpretation, the brain sends messages to the _________ to

bring about responses.

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muscles

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3 The brain consists of three main parts:

the ______________, the ______________ and

the _________________.

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cerebrum

medulla oblongatacerebellum

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4 The time between detecting a stimulus and being able to make a response is called the _______________.

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reaction time

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5 ________ may result when the brain interprets messages incorrectly.

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Illusion