The eye Flashcards
Receptors
Group of specialized cells
They detect changes in environment
Simulate electrical impulse in response
Sense organ
Group of receptors that respond to specific stimuli
Eye
Contains receptors that are sensitive to light and colour
Rod cells
Sensitive to light
Cone cells
Sensitive to colour
Cornea
Transparent lens- REFRACTS LIGHT AS IT ENTERS THE EYE
RETINA
Contains light receptor cells
Rods & cones
Optic nerve
Sensory neurone that transports impluses from brain to eye
Iris
Controls amount of light entering the eye
Pupil
Hole allowing light to enter the eye
Lens
Transparent disc that can change shape to focus light on retina
Pupil reflex
Reflex action that is carried out TO PREVENT DAMAGE OF THE RETINA
IN DIM LIGHT… (pupil reflex)
The pupil DILATES(widens) to allow as much light into the eye as possible.
In BRIGHT LIGHT( pupil reflex)
Pupils CONSTRICT(narrows) to prevent too much light entering the eye and damaging the retina
In bright light
Circular muscles contract and radial muscles relax so less light enters eye
In dim light
Radial muscles contract and circular muscles relax so more light enters into the eye.
Accommodation
Ways of fine focusing in lens
For a near object
Ciliary muscles-contract
Suspensory ligaments- slacken
Lens becomes fatter
More light is refracted
For far object
Ciliary muscles relax
Suspensory ligaments tighten
Lens becomes thinner
Less light is refracted
Rods
Sensitive to dim light
Cones
Sensitive to different colours of light
3 types of cones
Red
blue
green
Almost all cones are found in
fovea
Rods are found all over
Retina
Blind spot
Place where the optic nerve ATTACHES TO the retina BCS there are no light-sensitive cells there
