week 7 Flashcards
What is vison
Our most dominant sense
Assists with locating objects, in collaboration with other senses
What is Cornea
Clear; main lens of the eye
What is aqueous humour
watery fluid in anterior chamber
What is the iris
our eye colour
Pupil
dark aperture in front of the lens
What is lens
Adjustable lens to supplement cornea
What is ciliary body
includes ciliary muscle, which controls shape of lens; manufactures aqueous humour
What is vitreous humour
Jelly-like liquid between lens and retina
What is Extraocular muscles
attached to sclera move the eye
What is the path of light into the eye
Light enters directly through pupil, hitting light sensitive receptors at back of retina
What is path of vison the cornea to the retina
As light enters, it’s bent by the cornea, travels through the pupil, and bent again by lens. Curvature of cornea is fixed, muscles adjust curvature of lens to focus on near/far objects, Creates an inverted, backwards image
What does the lens do
emmetropic-normal vision
Vision problems occur when the focal point of light refraction is in front or behind the retina causes blurred vision
Bad lenses
Hypermetropic eye-long-sighted vision this is called by Hyperopia. It is corrected with a converging lens
Myopic eye-short-sighted vision called Myopia. This is corrected with a diverging lens
Effect of age on the eye
Presbyopic eye- sad, old people’s vision
Lens is no longer flexible enough to change shape can no longer focus on close and distant objects
What is Retina
Composed of photoreceptors with layer of neurons connected on top
Light passes straight to the photoreceptors at the back of retina, Neurons and receptors translate light into action potentials
What is Fovea
0.3 mm in diameter, centre of vison field
A small dimple in the retina denser receptors at centre
Sharpest vison, densest colour receptors
Makes reading possible
What is the blind spot
small area of retina where the blood vessels enter and exit. It has no photoreceptors
What is photoreceptors
Light triggers chemical reaction change membrane potential
two types: cones- tapered at end, 6-7 million
Rods- long cylindrical shape at one end, 120 million
What is the structure of photoreceptors with colour
small, densely packed, distinguish colours in bright light
What is the structure of receptors for colour (black and white)
Larger and more scattered, have 2 mile sensitivity to a single slight source
What are rods
very sensitive to low luminescence
Works in broader spectrum of conditions: Night vision: slow dark adaptation, low acuity, starts at periphery
None in Fovea
has only one colour receptor rhodopsin
What are cones
Don’t respond to dim light but very responsive to bright light
they detect colour and help us see fine detail: high acuity
Highly concentrated in fovea
Has 3 colour receptors red, green and blue
What is colour
red , green, red (cones) and light (rod)
roughly equal red and green
less blue, so not as sensitive
colour is a mixture-> they aren’t separate
Colour blind
Coded on X chromosome because of this men are more likely to be colour blind and women sometime s have more distinctive colour vision
