Vision Flashcards
1
Q
Describe focusing
A
- lens (along with cornea and humours) bends light entering the eye and focuses it on the back of the eye
- note: image is revived in reverse and proceeded into the right orientation in the brain
2
Q
How do we focus on different objects?
A
- ciliary muscles adjust shape of lens
- to focus on a distant object, muscles relax (and ligaments tighten) and lens flatten - lens is bent at a sharper angle
- to focus on a near object, the muscles contract (and ligaments relax) and the lens becomes round - light is bent at a wider angle
3
Q
What are photoreceptors?
A
- rods: very sensitive to light sensitivity
- cones: sensitive to color
4
Q
Describe rods:
A
- make up 95% of photoreceptors
- extremely sensitive to light
- detect various shades of black and white
- detect motion
- responsible for peripheral vision
- more concentrated on outside edges of retina
5
Q
Describe cones:
A
- detect color
- most are the fovea centrais
- require intense light for stimulation (this is why we only see black and white when the light is low)
- help us see detail (such as words on a page)
6
Q
Describe the three types of cones
A
- the three types of cones allow us to see different wavelengths of light
- blue, red, green
- using combinations of these cones allow for us to see many different colors
7
Q
Describe the translation of light into nerve impulses
A
- Rods contain rhodopsin cones contain photopsin, these are light absorbing pigments
- when a photoreceptor absorbs light, the pigment splits, which inhibits an inhibitory neurotransmitter (allowing a signal to be transmitted)
8
Q
What is the nerve signal pathway
A
- Rods and cones
- Biopolar nerve cells
- Ganglion nerve cells
- Optic nerve (formed by axons of ganglion cells
9
Q
How do impulses from the optic never get to the brain
A
- Optic nerve
- Thalamus
- Signal from right side of eye goes to right occipital lobe
- Signal from left side of eye goes to left occipital lobe
- Result is image in stereo (binocular vision)
