The Eye Flashcards
(24 cards)
Retina
Made up of light-sensitive receptor cells - rods and cones
Rods detect light intensity
Cones detect colour
Ciliary muscles
Ring of muscle that contracts and relaxes to change the shape of the lens
Suspensory ligaments
Ligaments that connect the ciliary muscle to the lens
Lens
Focuses light rays on to the retina
Cornea
Transparent region of the sclera at the front of the eye
Refracts (bends) light as it enters the eye
Vitreous humour
Keeps the eyes structure
Pupil
The hole in the centre of the iris that allows light to enter the eye
Optic nerve
Sensory neurone that carries electrical impulses from the retina to the brain
Sclera
The rough outer layer of the eyeball that helps keep the eye in shape and provides a place of attachment for the muscles that move the eye
Iris
Has sets of muscles that control the size of the pupil and thus how much light enters the pupil
Regulates the light reaching the retina
Also the coloured part of the eye
Fovea
A region of the retina with the highest density of cones (colour detecting cells) where the eye sees particularly good detail
Aqueous humour
Watery liquid between the cornea and the lens
Vitreous humour
Jelly-like liquid filling the eyeball
Choroid
A pigmented layer of tissue lining the inside of the sclera that prevents the reflection of light rays inside the eyeball
Blind spot
Point at which the optic nerve leaves the eye, where there are no receptor cells
Rods
Works well in darker/dimmer light
No ability to distinguish colours - brain will see a black and white image
Contain one type of photopigment - why we struggle to see colour in dim light
Cones
Works well in brighter light
Distinguishes colour - red green and blue
Wavelengths red, green and blue - if all stimulated white is created, if not we see different colours
What are rods and cones
Specialised cells
Send impulses to the brain via the sensory neurones in the optic nerve
What happens in dim light
Pupil dilates - allow as much light to enter as possible to improve vision
Circular muscles relax
Radial muscles contract
Amount of light entering increases
What happens in bright light
Pupil constricts to prevent too much light entering and damaging the retina
Circular muscles contract
Radial muscles relax
Amount of light entering decreases
Accommodation definition
The ability to for the eyes to change focus by changing the shape of its lens to focus on objects that are located at different distances
How does the eye accommodate to allow us to see an object far away?
Ciliary muscles relax
Suspensory ligaments tighten
Lens becomes flatter
Light is refracted less
How does the eye accommodate to allow us to see an object close up?
Ciliary muscles contract
Suspensory ligaments loosen
Lens becomes fatter
Light is refracted more
conjunctiva
lubricates and protects the surface of the eye
