The Eye Flashcards
What is the aqueous humour?
A fluid found behind the cornea
Maintained by lymphatic system
Provides nutrients to the cornea
Helps focus light into eye
What is the vitreous humour
Jelly like fluid
Fills up the eye
Involves in focussing
What is a conjunctiva
A curve under the eyelid which prevents dirt from getting to the back of your eye
Where is the blind spot?
A part of your eye in the back where no neurons or light are present
What is the cornea
Clear
Glass-like tissue
A specialized part of the sclera
Helps focus your vision by refracting light
Made of living cells
No blood vessels but gets oxygen from air surrounding it and releases CO2
What is the sclera
White of the eye Tough and rubbery Protection Maintains shape of eye Sites for muscle attachment
What is the retina?
Very thin
Responsible for detecting light
Contains photoreceptors
What is the choroid?
Absorbs all light that is not absorbed by retinal layer - why pupil is black
What is the iris?
Controls the amount of light that comes into the eye
Contains a sphincter
What are the purpose for the ciliary body and ciliary ligaments?
To focus light into the eye
What is a lens
Living cells
Very low metabolism
Rubbery - can change shape
What happens when light passes through a substance?
It refracts
How does a substance effect refraction?
The thicker the substance the more it refracts?
When objects are close to the eye, we have to bend the light _______.
More
In order to reflect the light more we have to make the lens ________.
Thicker
If the ciliary muscle is contracted, it will ________ the tension on the ligaments and the lens gets _________.
For close objects
Decrease
Thicker
If the ciliary muscle is dial aged, the ligaments ______ and the lens gets ________.
For far objects
Tighten
Thinner
What is accanodation
Focus plus light adjustment
What neurons (cells) do the photoreceptors send their signal to?
Photoreceptors -> bipolar cells -> ganglion cells
What are the 2 types of photoreceptors?
Ross and cones
What pigment is in rods and cones?
Rhodopsin
What is rhodopsin is broken down into?
Retinal (retinine - vitamin A)
Opsin (protein)
Types of opsin?
Regular
Short
Medium
Long
What differs in the types of opsin?
React with different wavelengths of light
What is special about the regular opsin?
Reacts with all wavelengths of light
How is rhodopsin formed?
An enzyme puts the Belen down parts (retinal and opsin) back together
Takes about 2 hours
What does retinal do?
When present Na channels open creating an action potential.
What opsin do Ross contain?
Regular
React with all wavelengths
Black and white vision
Are rods extremely light sensitive?
Yes
What are rods responsible for?
Night vision
All is us to see in low light conditions
Where are rods mostly found?
Peripheral vision around the outside of the eye
Where do rods send their signals to?
The occipital lobe
What type of motion do rods see?
Organic motion
Moving, loving things
What are rods good at detecting in bright lights
Edges and shadows
What do rods share that causes low resolution?
Bipolar cells
What is another word for resolution?
Aquity
There are three types of cones containing different types of opsin. These are?
Short - blue
Medium - green
Long - short
Each one reacts with a different section of the light spectrum
How many wavelengths does one cone react with?
One wavelength.
Are cones light sensitive?
Not as much as rods
What are the primary colours of light?
Green
Red
Blue
Rods don’t share these, causing them to have a high resolution
Bipolar cells
Where are cones located?
Packed in the centre
What is the fovea centralis?
Centre focus area
Packed with cones
Best vision
What is the blind spot?
No vision
No rods or cones
What is binocular vision?
Two eyes - each seeing a different image and the brain combines them into one
What is the optic chiasma?
Cross of the optic nerves
How many sides does the retinal later on each eye have?
Two sides
How do we have depth perception?
We rely on visual cues.
Name the four visual cues
Motion parallax Converging lines Overlay Relative size Shadows/Textiles/Gradients
What is motion parallax?
Objects further away appear to move slower through your field of view
What are converting lines
Corners that tell us what is close and far
What is overlay
One thing is obscuring another thing
Ex. Buildings in front of each other
What is relative size?
Objects that are small are generally farther away
What do Shadows/Textiles/Gradients tell us about depth?
Lose texture when something is further away
What causes a negative afterimage?
Fatiguing a specific cone
Can no longer see that wavelength of light
What causes a positive after image?
Over stimulation of rods and cones
Ex. A camera flash
What are the three layers of the eye?
Sclera
Choroid
Retina
