The Eye Flashcards
How many layers does the wall of the eye consist of?
Three Layers
Name the three layers of the eye.
The sclera, choroid and retina.
What are the functions of the sclera?
The sclera protects the inner eye.
The sclera maintains the shape of the eye.
What is the function of the cornea?
The cornea permits light to enter the eye.
The cornea refracts light rays so as to focus them on the retina.
What is the function of the choroid?
The pigment within the choroid prevents reflection of light within the eye by absorbing the light.
Suspensory ligaments arising from the ciliary body hold the lens in position
The ciliary muscles help alter the shape of the lens for near and distant vision.
The iris has radial and circular muscles, which controls the size of the pupil.
The pupil is able to control the amount of light entering the eye.
How many light receptors does the retina have? Name them.
2, Rods and cones.
What is the blind spot?
Is the area of the retina from which the optic nerves arises, contains no receptors and therefore it is not sensitive to light.
What is the function of the retina?
The retina is the light sensitive area of the eye where images are formed.
The rods a responsible for the vision of dim light whilst the cones are responsible for bright light vision and colour vision.
Function of the lens?
The shape of the lens can be altered for near or distant vision.
The lens refracts light rays entering so as to focus them on the retina.
Function of the aqueous humour.
It maintains the shape of the cornea.
It supplies the lens and cornea with food and oxygen.
It plays a minor role in the refraction of the light
Function of the vitreous humour
It maintains the shape of the eyeball.
It plays a minor role in the refraction of light.
Function of the eye.
Light reflected from objects passes through the cornea, aqueous humour, pupil, lens and vitreous humour and falls the retina where an image is formed. The receptors pick up the stimulus and convert to a nerve impulse. The impulse are conveyed to the optic nerve which transmits the impulse to the cerebrum of the brain. Here the impulse is interpreted. The eye is able to adjust to the distance of the object from the eye (accomodation) as well as to the light intensity (pupillary mechanism).
Define accomodation.
The ability of the eye to alter the shape of the lens to ensure that a clear image always falls on the retina, whether the image is near or distant.
Describe the accommodation for near vision.
The ciliary muscles contract The suspensory ligaments become slack The tension on the lens decreases The lens becomes more convex The refractive power of the lens is increased
Describe accommodation for distant vision.
Ciliary muscles relax Suspensory ligament become taut Tension on the lens decreases The lens becomes less conex The refractive power of the lens is decreased
