B3.1.3 - The Eye Flashcards
What is the eye?
The sense organ that allows you to see
Name the main structures of the eye.
Cornea, pupil, iris, lens, ciliary body, suspensory ligaments and optic nerve
Describe the cornea and its function.
A transparent coating on the front of the eye which protects the eye and refracts light entering the eye
Describe the iris and its function.
A coloured ring of muscle tissue which alters pupil size by contracting or relaxing
Describe the pupil and its function.
A central hole in the iris which allows light to enter the eye.
Describe the lens and its function.
Transparent biconcave lens which focus light clearly onto the retina.
Describe the ciliary body and its function.
A ring of muscle tissue which alters the shape of the lens
Describe the suspensory ligaments and its functions.
Ligament tissue which connects the ciliary muscle to the lens
Describe the optic nerve and its function
Nervous tissue which carries nerve impulses to the brain
How are images formed on the retina?
The cornea refracts incoming light rays which provides most of the focus to the incoming light, which passes through the pupil and is then further refracted by the lens, creating a sharp image on the retina.
What is meant by the term ‘refracts’?
Changes the direction of
What happens after a sharp image is on the retina?
Photoreceptors produce a nervous impulse due to the exposure of light which travels down the optic nerve to the brain, which interprets the impulses as a visual image.
What are photoreceptors
Light sensitive cells in the retina
What happens to the lens when your ciliary muscle contracts?
It becomes more convex (can focus on nearby objects)
What happens to the lens when your ciliary muscle relaxes?
It becomes less convex (can focus on distant objects)
What is short sightedness caused by?
A persons lens being too strong or by the eyeball being too long
What is long sightedness caused by?
A persons lens being too weak or eyeball being too short
What can be prescribed to correct long / short sightedness?
Glasses or contact lenses
How do glasses / contact lenses affect vision?
Corrected short sight - Concave Ken’s bends the light rays outwards before they enter the eye
Correct long sights - Concave lens bends the light rays inwards before they enter the eye
What do you call someone who has difficulty making out different colours?
Colour blind
What are the two types of photoreceptor cells that a retina has?
Rods and Cones
Describe the rods of photoreceptors.
Respond to light and allow you to see in low light conditions
Describe the cones of photoreceptors.
Respond to different colours. There are different cone cells that respond to red, blue and green light
What is the most common form of colour blindness?
Red - green
How do you get colour blindness?
Genetically inherited
