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THE EYE
HOW THE EYE WORKS
Sense Organs
Eye - SIGHT
Sensitive to light
Nose - SMELL
Sensitive to chemicals in the air
Ear - Hearing
Sensitive to sound
INTRODUCTION
Tongue - Taste
Sensitive to chemicals in food and drinks
Skin - Touch
Sensitive to pressure, temperature and pain
"In the blink of an eye"
Blinking center in brain and multiple muscles control reflexes of blinking
FACTS
BLINK
Each time we blink, a protective coating of tears is spread like a film over the front of our eye.
ommatophobia
Fear of eyes
EYES is the WINDOW TO THE BRAIN
Eye is the sense organ of sight.
The eye is shaped like a ball and is located in bony sockets
in the skull
Look into my eyes!
Receptors
Respond to specific stimuli
Electrical impulse
Nervous system
Respond
Sense Organs & Brain
The nervous system and the important sensory organs play a key role in the day-to-day functioning of an animal.
EYE ANATOMY
PARTS OF
THE EYE
PARTS OF THE EYE
HOW EYES WORK
EYE ANATOMY
Front
view
materials
Sclera
Iris
Pupil
EYE ANATOMY
Sclera
The white of the eye, tough layer for protection and shape
Choroid
Contains blood vessels that supply nutrients to eyes
Cornea
A transparent layer, refracts light into the eye
Retina
Contains light receptors
(Receive light lens has focused)
Fovea
Provides the clearest vision of all
Allows light into the eye
Pupil
Colored section of eye, controls the amount of light
Iris
Carry electrical impulses from the retina to the brain
Optic nerve
A transparent disc, can change shape for focusing
Lens
Ciliary muscle
Enable the lens to
change shape
Blind spot
Area where the optic nerve and blood vessels leave the eyeball and with no light-sensitive cells
Suspensory ligaments
Connect the ciliary muscle with the lens and thus holding it in place
HOW?
STEP 3
The lens focus the light and send it to the back of your eyes.
STEP 2
Iris changes the size of pupil depending on how bright the light is.
STEP 4
Retina translate the light into electrical signals
STEP 1
Light enters the eye through cornea.
STEP 5
The optic nerve is responsible for carrying the signals to the brain.
IRIS
Tiny muscles that make up iris
relax and contract
to maintain a fairly constant
level of light entering the eye.
Pupil Reflex
PUPIL
Circular muscle
Radial muscle
The Pupil Reflex
In dim light,
the pupil dilates (becomes larger) to allow more light to enter the eye to improve vision.
Circular muscles & Radial muscles work antagonistically.
Pupil
Contraction
Dilation
In bright light,
pupil constricts (gets smaller)
to allow less light to enter the eye
to protect the retina from damage.
Pupil Reflex
Visual Accommodation
Distant Vision
The ability of the eye to change its focus from distant to near objects (and vice versa),
by the lens changing its shape.
Ciliary muscles are relaxed
Suspensory ligaments stretched thin
Lens to become thinner (flatter)
Light is refracted less,
eyes focus on a distant object
Accomodation
Distant Vision
Light rays from distance objects are parallel, so do not need much refraction
Near Vision
Ciliary muscles &
suspensory ligaments
work antagonistically
Light rays from closer objects are diverges, so need much refraction
to focus properly
Near Vision
Ciliary muscles are contracted
Suspensory ligaments slacken
Lens to become thicken (rounder)
Light is refracted more,
eyes focus on a close object
Photoreceptor Cells
Detect change in environment
Rod cell
Cone cell
PHOTORECEPTOR CELLS
Rod cell & Cone cell
Photoreceptor cells
Rod cell
Cone cell
Conical shaped
Cylinder shaped
Rod cell &
Cone cell
Color vision in bright light
Sensitive to low light intensity
Monochromatic night vision
Sensitive to low light intensity
We are
different
Concentrated at the fovea
Evenly distributed over retina & absent
at the fovea
QUIZ
When shine the light to the pupil, describe the change to the eyes. Explain why the change you described is necessary.
(5%)