Lecture 21 Flashcards
The ____ divides the interior of the eyeball into two chambers
lens
What are the 2 chambers of the eye?
- Anterior/ Aqueous Chamber
- Posterior/ Vitreous Chamber
Where is the cornea located?
it is the transparent bulge at the front of the eye, continuous with the white of the eye, or sclera — the outer wall of the eyeball
What helps maintain the eyeball’s shape?
Behind is the vitreous chamber, filled with the vitreous body, a clear jelly
The role of the Cornea and Lens
focus light on the retina, the inner lining of the eye that contains the photoreceptors.
Where does light pass from the cornea to the lens?
Through a hole in the iris (the pupil)
In which order does light travel into the eye?
Cornea, pupil, iris, lens, retina
What is the Sclera?
the white outer coating of the eye
What is the role of the pupil?
- controls depth of field (the focus)
- helps to focus light
What controls pupil dilation?
- parasympathetic cells and sympathetic cells through the pupillary constrictor muscle and the radial pupillary dilator muscle of the iris
What happens when the eye is exposed to bright light?
- parasympathetic signals from the brain contract the pupillary constrictor muscle - - shrinking the pupil
What happens when the eye is exposed to the dark?
- sympathetic signals contract the radial pupillary dilator muscle of the iris
- dilating the pupil
What happens to our depth of field when the pupil is tightly constricted/ not dilated?
we have full depth of field, i.e. everything we see is equally in focus.
What happens to our depth of field when the pupil is dilated?
we have a shallow depth of field, i.e. only objects near one specific distance are in focus
How can we get a retinal image that is both bright and in focus?
By using refraction.
Refractive index
The ratio of the speed of light in a vacuum to its speed in a specific medium
The higher the refractive index the _______ the light travels
slower
What are our corneas made of?
clear collagen
Why does clear collagen allow for strong bending of light/ refraction?
because there is a big difference between the refractive indices of air and collagen
The cornea is responsible for ____ of the eye’s refraction, and the lens for ____
2/3
1/3.
How can the lens adjust the focus of light?
through change in shape
Why is refraction in water weak?
the refractive indices of collagen and water are similar
What is the lens?
It is a mesh of long cells without nuclei, packed with clear proteins called crystallins, and “zippered” together in concentric layers for flexibility
What makes up the lens?
clear cells and have no blood supply, but absorbs nutrients from the aqueous humor.
