The Eye Flashcards
The eye is a sensory organ which detects…
Light
What is the cornea
Curved transparent disc at front of eye which does most of the focusing
What is the pupil
Circular opening whose size is controlled by the iris
What is the iris
Ring of muscle with the pupil in the middle Controls how much light enters the eye
What is the lens
Soft flexible and transparent Changes shape to fine tune focusing light onto retina
What are the ciliary muscles
Ring of muscle at edge of eye circling the lens. When muscle contracts the lens gets fatter. When muscle relaxes lens gets thinner. Allow eye to fine focus.
What are the suspensions ligaments?
Strong fibres which attach the lens to the ciliary muscle.
What is the retina
Contains light sensitive cells called rods and cones
What is the optic nerve
Consists of many neurones which carry impulses from retina to the brain
What is the fovea
Region of retina with greatest number of cones
What is the conjunctiva
Mucous membrane that covers the eye to prevent infection
What are the two types of muscle in the iris which allow its reflex action to control the size of the pupil and the amount of light entering the eye.
Radial muscles and circular muscles
Label the eye
How do we focus on a distant object?
- Cilary muscles relax which allows the suspensory ligaments to pull tight
- This makes the lens go thin
- This means it refracts the light by a smaller amount
How do we focus at near objects?
- Cilary muscles contract which slackens the suspensory ligaments
- The lens becomes more fat
- This increases the amount by which the lens refracts light
