t5- homeostasis- the eye Flashcards
what does the iris control
how much light enters the pupil
what does the lens do
further refracts light to focus it onto the retina
what does the cornea do
refracts light as it enters the eye
what does the sclera do
protects eye from injury
what does the retina do
contains the light receptors
what are the 2 light receptors in the retina
cones- sensitive to colour
rods- sensitive to low light intensity. allows us to see in dim light
what happens to the iris in low light intensities
radial muscles contract
circular muscles relax
what happens to the iris in high light intensities
circular muscles contract
radial muscles relax
what is accomodation
the process of changing the lens shape to focus on distant/near objects
what 3 things happen when an object is near
-the ciliary muscles contract
-the suspensory ligaments loosen
-the lens is then thicker and refracts light rays strongly
what 3 things happen when an object is far
-the ciliary muscles relax
-the suspensory ligaments are pulled tight
-the lens is then pulled thin and only slightly refracts light rays
what happens in short sightedness, and what is it called
myopia
-eyeball is elongated- distance between lens and retina is too big
-lens is too thick and curved- light is focused infront of the retina
how is short sightedness corrected
placing a concave lens infront of the eye
what happens in longsightedness and what is it called
hyperopia
-eyeball is too short- distance between lens and retina is too small
-loss of elasticity in lens-can’t become thick enough to focus
-light is focused behind the retina
