Lecture Flashcards
Insulin Resistant Diabetes
- with age, body stop producing insulin so there are circulation problems in the eyes
- capillaries beging to leak and bleed so it causes floaters in the vitreous humor
AGE RELATED
Neo-vasularization
- new blood vessels being to grow bc the eye uses alot of blood but these are abnormal and leak too so it accelerates the problem
- can scar retina and lead to blindness
- LIFESTYLE PROBLEM
Treatment for neo-vascularization (2)
1) retinal photocoagulation: use laser to kill off abnormal cells - SHORT TERM
2) ran-retinal phtocogaulation: use laser to burn off the retina so it uses less blood
Macular Denegeration
- cell sin fovea die and destroys cones - less detailed vision
- OCCURS WITH DIET AND AGE
Drusen
- white yellow bumps in between retina and pigment epitliu are afected - cones in fovea die off first
What test is used for macular degeneration?
- Amsler Grid Test: black dot in middle with lines - if you have macular degeneration then the lines look wiggly because cones are dying
2 types of macular degeneration:
1) Dry: progress slow and person may not notice - get eyes checked
2) Wet: loose your vision and neo-vasularization speed up loss of sight (leaks and cause floaters)
- will lead to blindness
What is the treatment for wet macular dengeration?
- Destroy the choloroid because it is responsible for nourishing blood
Describe hereditary retinal disorder
- affects the rods
- begins in teen - start noticing problems with night vision
- don’t see color in the far peripheral (no color in rods)
What is glucoma?
- When the acqueous humor lique gets trapped
- in between cornea and lens there is liqued but it gets blocked on the way out
2 types of glucoma:
Who is at risk for close gulacoma?
1) open angle: slow, on the way out it gets blocked and presure builds up and pushes against the vitreous humor and retinal ganglion cells
- can cause BLINDNESS
- can help control you BP
- most common type
2) close angle: the iris flops over and blocks the fluid so it developes really fast; can feel it = PUPILLARY BLOCK
- need to put a hole in iris so the fluid can esacpe = IRIDECTOMY
- asians and people with axial ayopia (short eyeballs) at risk
Afterimage
- image you see floating in front of eyes from an after-effect
After-effect
seeing one things influences what you see later
Using B&W; how does an after-effect occur?
- when your eye sees white it receives alot of AP so the white neurons get tired out and then you see black
- the dark neurons are not as tired so they can active AP where there is white space
What are 2 ways collector cells work?
1) conveergence: adding up actvity of many cells (more sensitive in dim light)
2) Spatial lateral summation
What is lateral inhibition?
- when cells are side by side they send inhibitory NT to eahother so that you can see edges
Describe the visual system of the Limulu scrab
- have lens retina pairs (similar to neurons) called ommaditium that are connecte to eachother with a laterla plexus
What are 3 illustions that demonstrate lateral inhibition
1) Mach bands - exaaggeration of edge in our perceptio
2) Herman Grid - the center of the interesection has inhibitory NT from all sides = small gray circle
3) Simultaneous contrast: the small sqaure in the white surronding looks darker because of laterla inhibition
Receptive field
- part of retinal image that cell response to
On/off response
On response: when there is light the cell produces more AP than baseline
- nothing happens in darkness
Off response: when the light is on it produces less AP than baseline
- nothing happens in the dark
2 types of retinal ganglion cells:
1) Parvo cell: small axon; color senstivity; high acuity; sustained response to stimuli (continuous responding)
2) Magno cell: faster bc axon is wide; motion; fewere m cells but many in periphery (fast response to a baseball coming towards the side of your head)
Retinotopic map
- sptial realtion in retina are presevered in brain (things closer toether in image = close together in brain )
Feedforward
- bottom up pocessing
- going from the eye to the brain and bi-directional
2 ways that coding can work:
1) specficity coding: firing of 1 neuron in response to specific stimuli (key to sensory coding)
2) distributed coding: cell respond to different degres to same stimli (can look at pattern of responding)
Tilt after effect
- when you stare at lines to the right for a long time these receptors get tired out so when you look at line that are vertal the right orientation is too tired to balance out the left orientation so the left is responding more strongly and makes the lines tilt to the left
Optic chiasm
- firs stop from the visual field that connects both visual fields
Suprachaismitc nucleaas
- first visual strcuture of the visual pathway hat controls circaidum rhythm to send signals to pineal gland and produce melatonin
Melanopsin
- special retinal gaanglion cell in the suprachaiastmic nucleas that tells us if we are sleeping or not (photopigment)
Center surrond antagonism
- if + in center and light hits center = more activity; light in exterior when exterior is - slows down actiity; light everyone = cancels out activity
What structure comes after optic chiams? Descirbe it and the system it belongs to
- superior colliculus: specailized for eye movements
- is part of the tecto-pulvinar system: has 10% of fibers and contains all m-cells
Extracular muscles:
- outside the eye and move eyes left and right
Fixation cells (superior colliculus)
- have Ap at stimulus when eye is fized at point
Build up cell (speruior colliculs)
- just before en eye movment = AP
burst cell (superior colliluc)
- when you are making eye movments = AP
Corrs-odel sensory
- integrates haring and visiion
Visual orientating reflex
- mediated by superior collculus; cross model because it itegrates hearing and vision to respon at once = communication between the 2
Geniculostatie system (2 components)
1) lateral geniculate nucleas
2) stratie cortex
LGN
- 90% of fibers that don’t go to tectno pulvinar system (superior colliculs) go here
- 1 on each side of braint hat controls what information gets in
- LGN reduces activity when you are tired
- senstive to state of arousal bc recieves information from reticular formation and reticular activing system
Layers of the LGN
- 6 layers
- 1 and 2 = m cells (input of motion)
- 3,4,5,6 = p cells (form and color)
- 1,4,6 = contalateral eye information (opposite eye)
2,3,5 = ispilateral eye information
Straite cortex
- AKA primary visual cortex, V1, Area 17
- main part of visual analysis (conscious perception)
- take information apart and does a feature analysis
Feature analysis
- looks at entie image and looks at aspects e.g. feature orientation and particular types of movemenet
Cortical magnification
- fovea cones ahve their direct line to ganglgion cells so the brain has a disporoption amount of area dedication to the foevea even thought fovea = 1/100% the brain area = 8% so you can see finer details
Scetoma (dmanage to V1)
- small spot of dmaage = gap in visiual field
Hemianopia (damange to V1)
- half of visual field is damange
Quadromanopia (dmaange to V1)
- quater of visual field is lost
What happens when the entir visiual field is dmanage?
- leads to cortical blindness
- they have blindsight that suggest that they can still see something (perhaps because 10% is going to the tecto-pulvinar system)