Unit 1: Perception & Dreaming

How do we see our world?

THE EYE!

Starter Activity

Keeping your eyes SHUT, take an item out of the bag. Without looking at it, what can you tell?

•What shape is it?•How big or small is it?•Feel it’s texture – is it hard/soft/furry/slimy ?•What else can we tell about it without using our eyes?•What can’t we tell about it? What colour is it?

Make a list!

Don’t need your eyes Need your eyes

Vision vs Perception

• What is the difference between them?

Vision:Our eyes work by

DETECTING rays of light that are reflected or emitted by objects.

This is a biological process that happens in

our eyes.

Perception:happens in our brain. It is a

psychological process during which our

brain makes sense of the visual image

detected by our eyes.

The Structure of the Eye

Draw and label a diagram of the eye

How do we see?

http://www.youtube.com/watch?v=kFzGvlFAp_w

How do we see?

1. Light is reflected off an object, enters the eye, and makes an image on the retina (the layer at the back of the eye).

2. The retina is covered with thousands of light-detecting cells called rods and cones.

3. The retina, which is very sensitive to light, sends nerve impulses to the brain. The nerve impulses travel along the optic nerve.

Chain of events

retina

Light is reflected off the object and enters the eye

The RetinaRods and cones are special nerve cells.

Using your textbook, make a table listing the differences between them.

Rods Cones

Table listing the differences between rods and cones

Rods Cones

Respond in dim light Work best in bright light

Detect light, shape and movement but not colour

Detect colour, but less sensitive to light than rods

ADDITIONAL INFO

Located on edge of retina Located in centre of retina

120 million in each retina 6 million in each retina

Responsible for detecting objects ‘out of the corner of your eye’

If there is not enough light, cones cannot detect the colour of an object.

Task ~ can you create a poem to help remember the main points!

What happens when you go to a movie?

Sequence of Events Rods Cones

1. You are outside in the bright sunshine, just about to go in to the movie theatre

2. You step into the theatre. You can’t see a thing! Your eyes haven’t adjusted to the dark. You can vaguely make out

3. After a few minutes, you can make out people and shapes, but no colours.

4. Movie finishes, and you step outside. It is too bright! It is difficult to see!

5. Finally, after a few minutes, your eyes adjust, and everything looks normal again.

What happens when you go to a movie?

Sequence of Events Rods Cones

1. You are outside in the bright sunshine, just about to go in to the movie theatre

- active

2. You step into the theatre. You can’t see a thing! Your eyes haven’t adjusted to the dark. You can vaguely make out

- active

3. After a few minutes, you can make out people and shapes, but no colours.

active -

4. Movie finishes, and you step outside. It is too bright! It is difficult to see!

active -

5. Finally, after a few minutes, your eyes adjust, and everything looks normal again.

- active

How do nerve impulses get from the retina to the brain?

• When enough light falls on a rod or cone in the retina, the cell responds by sending a nerve impulse to the brain.

• These impulses travel along the OPTIC NERVE. The optic nerve looks like a thick stalk at the back of the eye, and consists of nerve cells bundled together.

• Once information reaches the brain, whatever the eye has seen can be interpreted.

Chain of events

retina

Light is reflected off the object and enters the eye

brain

Nerve impulses travel along the optic nerve to the visual cortex

The optic nerve and the brain

• At the point in the retina where the optic nerve leaves the eye, there is no room for rods or cones. This area is called the ‘blind spot’, and it occurs in both eyes.

• Light landing on the blind spot is not detected by the eye. We don’t notice our blind spots, because they don’t overlap.

• If one eye can’t see something, the other one can.

• When you have both eyes open, you are never aware that part of each visual field is ‘missing’.

The blind spot

• To find your blind spot draw the image below on a scrap of paper

• Close your left eye.

• Hold the image (or place your head from the computer monitor) about 20 inches away. With your right eye, look at the dot. Slowly bring the image (or move your head) closer while looking at the dot. At a certain distance, the + will disappear from sight...this is when the + falls on the blind spot of your retina. Reverse the process. Close your right eye and look at the + with your left eye. Move the image slowly closer to you and the dot should disappear.