THE EYE Flashcards
tough outer coat that protects the eye?
sclera
layer of the eye that contains blood vessels, it nourishes the eye?
choroid
front portion of the eye, convex in shape, it bulges outside. light enetrs the eye through this part?
cornea
Coloured part of the eye, muscular diaphragm found behind the cornea. It regulates the amount of light entering the eye by adjusting the size of the pupil?
iris
Hole in the middles of the iris. The size of the pupil increases or decreases depending
on the amount of light entering the eye?
pupil
Made of transparent, jelly-like substance which is made of proteins. It is held in
position by the ciliary muscles and suspensory
ligaments?
lens
Thick liquid which fills the area between the cornea and the lens. It prevents the eye
from collapsing due to changes in atmospheric pressure?
aqueas humor
Membrane with a large number of 2 types of light sensitive receptor cells called rods
and cones/dect colour?
retina
The main nerve through which nerve impulse from receptor cells in the retina are sent
to the brain?
optic nerve
Jelly-like substance in the space between lens and retina, helps to maintain the shape
of the eye?
vitreous humor
Small region of the eye where the optic nerve enters the eye . It is insensitive to
light
blind spot
forming an image?
- Light passes through the eyeball to the retina.
- It is refracted (the rays are bent) by the cornea and lens, so that the light is brought to a focus on the retina.
- As a result of refraction the image on the retina is inverted.
- The brain interprets the image the right way up.
what is accomodation?
The changes that take place in the eye to allow us to focus on near and far objects is called
accommodation.
what happens to the cilary muscles when a object is near?
contract
what happens to the suspenosry ligaments when a object is near?
slackened
what happens to the lens shape when a object is near?
fat
what happens to the cilary muscles when a object is distant?
relax
what happens to the suspenosry ligaments when a object is distant?
stretched
what happens to the lens shape when a object is distant?
thin
In bright light the pupils are constricted.
Why?
To reduce amount of light entering the eye to avoid
damage to the retina
In dim light the pupils are dialted.
Why?
To allow as much light as possible to fall on the
retina to maximise vision
the iris?
The iris has circular and radial muscles that work
antagonistically to either constrict or dilate the pupil.
In bright light the circular muscles contract and radial muscles
relax, so the pupil is constricted.
In dim light the circular muscles relax and radial muscles
contract, so the pupil is dilated.
iris reflex?
The constriction and dilation of pupils is an example of a reflex action.
Note: the reflex action of either eye controls the
constriction an dilation of pupils of both eyes (i.e. a bright
light shone into one eye will cause the pupils of both eyes to
constrict).
