Vision Flashcards
1
Q
Cornea
A
- front of eye
- clear, dome-like structure that allows light to enter into eye
- gathers and focuses incoming light
2
Q
Pupil
A
light for cornea enters this gap in the iris
3
Q
Iris
A
- color portion of the eye
- regulates size of pupil with its contractile muscles – smaller iris = larger pupil and vice versa
4
Q
What happens to pupil when exposed to bright light?
A
- pupil will constrict to protect retina
- involuntary muscles in iris relax
5
Q
What happens to pupil in the dark?
A
- pupil will dilate to get more light into retina
- involuntary muscles in iris contract
6
Q
Lens
A
- located behind the iris
- focuses/refracts light to create a focal point
7
Q
Fovea
A
- focal point of light located at the back of the eye
- only cones located here, no axons
8
Q
Retina
A
- located at back of eye, innermost layer of eye
- translates photons in light into an electrical impulse that is transmitted to body via neurons
- “image detector”
9
Q
Optic Nerve
A
sends information from retina to brain
10
Q
Retinal Cells
A
- rods and cones
- light absorbing cells of the retina
- responsible for transduction of photons into an electrical signal
11
Q
Structure of Rods and Cones
A
- contain mitochondria and nucleus
- light absorbing portion (membrane shelves lined with rhodopsin) face back of the eye
- specialized synapse facing front of eye so they can transduce electrical signal to other cell types that carry signal to optic nerve
12
Q
Rods
A
- contain single rhodopsin pigment
- low sensitivity to detail
- permit night vision
- no color perception
- normally turned on but turn off when light hits
- mostly found in periphery
- slow recovery time
13
Q
Cones
A
- contain 3 different types of photopsin pigments
- sensitive to both color and detail
- absorb light in red/green/blue spectrum
- best in bright light
- concentrated at fovea
- fast recovery time
14
Q
Bipolar Cells
A
- first cells that receive light
- direct input from rods/cones
- highlight gradients
- pass signal to ganglion cells
15
Q
Horizontal and Amacrine Cells
A
- two cell types that affect the bipolar cell before they send signal to ganglion cells
- work together to take information from multiple retinal cells to detect edges and contrasts
16
Q
Ganglion Cells
A
- receive information from many retinal cells
- group to form the optic nerve
17
Q
Conjunctiva
A
first layer of eye that light hits
18
Q
Anterior Chamber
A
- space in eye that is filled with aqueous humor
- provides pressure to maintain shape of eyeball
19
Q
Sclera
A
- whites of eye
- thick fibrous tissue covers posterior 5/6th of eyeball
- attachment point for muscles
- does not cover cornea
20
Q
Choroidal Vessels
A
blood vessels that supply nutrients to the eye along with the retinal vessels
21
Q
Posterior Chamber
A
- area behind cillary muscle
- filled with aqueous humor
22
Q
Dilator Pupillae
A
opens pupil under sympathetic stimulation
23
Q
Constrictor Pupillae
A
constricts pupil under parasympathetic stimulation
24
Q
Blind Spot
A
- located where the optic nerve connects to the retina
- no rods or cones found here
25
Macula
part of retina that is rich in cones
26
Ciliary Body
- portion of eye that produces aqueous humor
| - accommodation of lens
27
Canal of Schlemn
drains aqueous humor
28
Suspensory Ligaments
- change shape of lens
| - if ciliary muscle contracts it pulls on these
29
Vitreous Chamber
- filled with vitreous humor
| - jelly-like substance that provides pressure to eyeball
30
List the structure of the eyeball in order of where light enters
1. cornea
2. pupil
3. lens
4. vitreous
5. retina (rods/cones -> bipolar cells -> ganglion cells)
6. optic nerve
7. optic chiasm
8. optic tract
9. LGN of thalamus
10. radiations through parietal and temporal lobes
11. visual cortex in occipital lobe
31
Magnocellular Cells
- located in the LGN of the thalamus
| - responsible for motion
32
Parvocellular Cells
- located in the LGN of the thalamus
| - responsible for shape
33
Optic Discs
- found in rods
| - large membrane bound structures that contain proteins that fire APs to brain
34
Describe the pathway that occurs when light hits rod/cone
1. light hits small molecule called retinal inside of protein rhodopsin and causes retinal to change conformation from bent to straight
2. transducin breaks from rhodopsin and alpha from transducin binds to phosphodiesterase (PDE)
3. PDE converts cGMP to GMP which leads to closing of Na+ channels (occurs b/c Na+ channels need bound cGMP to open)
4. rods hyperpolarize and turn off; glutamate is no longer released and no longer inhibits ON bipolar cells
5. ON bipolar cells activate retinal ganglion cell which sends signal to optic nerve in brain
35
Optic Chiasm
- where nasal fibers from left and right eye cross
| - visual information from left side of each eye goes to left hemisphere of brain
36
Everything in ____ visual field is processed by the left hemisphere and vice versa.
right
37
List the 3 areas of the brain where vision is processed
(1) lateral geniculate nucleus: part of thalamus
(2) visual cortex: part of occipital lobe
(3) superior colliculus: midbrain, constitutes tectum
38
Parallel Processing
- ability to identify key characteristics in an image and apply those characteristics to a memory in order to recall a word or title to describe the object in the image
- Ex. see picture of cheetah and recognize tan fur, small black spots etc then recall and associate word "cheetah"
39
Feature Detection
- recognition of features to identify desired object in visual field
- Ex. how do you find a friend in a crowd? if friend said they have green shirt on then brain automatically filters and focuses on people wearing green
