Eyes and Vision Flashcards
What is monocular vision
Usually found in prey
Each eye has wider field of view so animal can see to each side and behind and in front (almost 360’)
Little overlap in field of view so difficult to judge distance or speed
What is the purpose of the iris
Controls amount of light entering the eye
What is the purpose of the retina
Contains receptor cells which are sensitive to light
These carry nerve impulses to the brain
What is the purpose of the lens
Focuses light on the retina, changes shape
Surrounded by circular ciliary muscles that change the shape (accomodation)
Suspensory ligaments attach lens to ciliary muscles
What is the purpose of the cornea
Refracts light
What is the purpose of the optic nerve
Carries impulses via sensory neurones to brain
What does the pupil do
It is made bigger or smaller by the iris
What does the eye do when light rays are reflected by a DISTANT object
(Rays almost parallel)
Ciliary muscles relax
Suspensory ligaments become taut
Lens long and thin
Light only refracted a little to focus on the retina
What does the eye do when light rays are reflected by NEAR object
Rays diverge in all directions
Ciliary muscles contract
Suspensory ligaments slacken
Lens short and fat
Light refracted to focus on retina
What is long sight caused by and how is it corrected
Seeing distant objects not close
Eyeball too short or
lens thin and flat not fat and short (not changing shape properly)
Corrected by CONVEX lens which converges and focuses on the retina
What is short sight caused by and how is it corrected
Seeing close objects not distant
Eyeball too long or
weak suspensory ligaments (lens is fat and short not thin and flat)
Corrected by CONCAVE lens that diverges light rays to focus on retina
How do we see something
What is the process starting with light focused on the retina and ending with the brain interpreting an image
The eye focuses light onto the retina
lens and cornea refract the light to converge at a focal point on retina
Light sensitive receptor cells in the retina, are stimulated
They pass an impulse along the sensory neurones to the brain
The brain then interprets the impulses (perception)
How does binocular vision help judge distances
It compares images from each eye
The more similar the images, the further away the object
When looking at distant objects, how are light rays reflected from the object when they reach the eye
The light rays are almost parallel when they reach the eye
When looking at near objects, how are light rays reflected from the object when they reach the eye
The light rays diverge (reflected out in all directions)
