EYES Flashcards
retina
a tissue at the back of the eye that contains receptor cells that respond to light
optic nerve
the nerve that carries electrical impulses from the retina to brain
blind spot
the part of the retina where the optic nerve leaves, and where there are no receptor cells
forvea
the part of the retina where cone cells are very tightly packed; this is where light is focused when you look directly at an object
What are rod cells sensitive to?
They’re sensitive to light at LOW INTENSITIES.
Rod cells are more sensitive to light than cone cells.
They do NOT detect colour.
What are cone cells sensitive to?
They’re sensitive to COLOUR and light at HIGH INTENSITIES.
Humans have 3 different types of cone cells, each sensitive to a different range of colours (ones which respond to red, green or blue)
What type of organ is the eye?
A sense organ
How does the eye focus on distant objects?
Ciliary muscles relax, eyeball becomes more spherical
Suspensory ligaments tighten, pulling lens thin
To focus distant objects, the lens must be thin so light rays are only slightly refracted
How does the eye focus on close objects?
Ciliary muscles contract, pull eyeball inwards (bulges forward)
Suspensory ligaments loosen, causing the lens to thicken
To focus on close objects, the lens needs to be thick to refract the light rays greatly
iris
coloured part of the eye; it contains muscles that can alter the size of the pupil
pupil
circular gap in the middle of the iris, through which light can pass
iris reflex
an automatic response to a change in light intensity; the receptors are in the retina, and the effector in the muscles in the iris
antagonistic muscles
a pair of muscles whose contractions has opposite effects; when one contracts, the other relaxes
refraction
bending light rays
cornea
the transparent layer near the front of the eye, which refracts light rays entering the eye
