Section 2 - Cells and control - The Eye Flashcards
Function of the cornea?
Refracts light into the eye
Function of iris?
Controls how much light enters pupil
Function of lens?
Refracts light, focusing it onto retina
Function of retina?
Light sensitive part and covered in receptor cells called rods and cones, which detect light
Function of rods?
More sensitive in dim light but can’t see colour
Function of cones?
Sensitive to different colours but aren’t so good in dim light
Function of optic nerve?
Carries electrical impulses from receptors to brain
When looking at distant objects, what happens to the lens?
Ciliary muscle relaxes, allowing suspensory ligaments to pull tight. This pulls lens into less rounded shape so light is refracted less
When looking at close objects, what happens to the lens?
Ciliary muscle contracts, which slackens suspensory ligaments. Lens becomes more rounded shape, so light refracted more
Why are long-sighted people unable to focus on near objects?
Lens is wrong shape and doesn’t bend light enough or eyeball too short. Light from near objects brought into focus behind retina
How to correct long-sightedness?
Use glasses or contact lenses with convex lens
Why are short-sighted people unable to focus on distant objects?
Lens is wrong shape and bends light too much or eyeball too long. Light from distant objects brought into focus in front of retina
How to correct short-sightedness?
Use glasses or contact lenses with concave lens
How is red-green colour blindness caused?
When red or green cones in retina aren’t working properly
What is a cataract?
A cloudy patch on lens, which stops light from being able to enter eye normally, making vision blurry, sometimes colours less vivd and difficulty seeing in bright light.
