Lecture 9: Vision

Question 1

Reception

Answer 1

• you see things
• going to receive information —> activate those sensor receptors
• sensor receptors for vision —> in your eyeballs

Question 2

Transduction

Answer 2

• making that action potential + synaptic communication via those chemicals —> communication between the neurons
• changing that stimulus energy, taking into consideration for vision
• stimulus energy —> photons, light
• change it into action potentials and chemicals to help ourselves out with regards to neurons talking to each other

Question 3

Coding

Answer 3

• primarily takes place for your sense of vision in your occipital lobe
• all about photons of light —> the stimulus energy in the first place
• However you are perceiving your visual world —> all about light + many wavelengths of light that are going to be bouncing off particular objects
• As you’re looking at me —> light from outside, light from above that’s hitting me —> projecting into your eyeball
• mostly trying to get the photo receptors —> back wall of your eyeball on retina —> to become activated
• if we expand or magnify the wall of the retina —> have to get light to hit it at a 90 degree angle/ a perpendicular angle in order to activate those photoreceptors successfully

Question 4

Cornea

Answer 4

• most superficial layer out the front here
  
  • protection
  • special almost skin like cells —> able to regenerate and heal in that way —> just like your skin helping you out with protecting your eyeball
  • transparent —> light can come on through
  • We have light usually coming in at this particular coloured pot of your eye —> Iris

Question 5

Pupil

Answer 5

• Middle of your iris
• no anatomical structure —> just a hole
• However big your iris —> what you perceive as being your pupil
• Size of your pupil
  
  • Go into a dark room —> larger —> pupil dilation
• function —> controlling the amount of light coming into your eye
  
  • brightly lit room —> pupil get smaller —> Pupil constriction —> letting less lighting in —> helping you to see
• get past the pupil —> controlling the amount of light

Question 6

Glasses

Answer 6

• Near sighted —> eyeball is too long, an eyeball growth —> even though your lens does what it can, it incorrectly refracts the light into the vitreous humour space (gel like substance that makes up the majority of your eyeball)
  
  • in advance or well before the actual photoreceptors
  • near sightedness —> bring things closer to us so that our lens doesn’t have to work quite so hard
  • When people squint —> can see better
    
    • squishing their eyeballs —> your eyeball is too long —> eyeball has a lot of muscles around it —> able to be in order to improve it
  • Near sightedness —> you can see with the addition of glasses —> ends up refracting it in slightly different ways —> help you out with regards to getting it onto the back wall —> onto your retina in turn
  • interocular pressure
• Far sighted —> eyeball a little bit short
  
  • Instead of getting projected onto your retina —> gets well past the point
  • 25 to 30 —> eyeball will eventually stop growing
  • As you get older again —> eyeball starts to get a little bit stiff
  • Older people have bifocals on their glasses —> both nearsightedness and farsightedness on their glasses

Question 7

Lens

Answer 7

• in charge of refracting the light appropriately onto your back wall —> can change shape
• Look on either side of it —> has a couple of types of muscle that can contract/relax depending on how far away an object is
• Change in the shape of the lens is what happens when we’re trying to actually focus on a particular object
• Your lens gets a little bit thinner when looking at things further away —> bc the muscle contracts and it changes the shape
• Closer to you —> lens gets a little bit fatter to accommodate
• Whole accommodation of the lens is helping to focus appropriately that bit of light onto your back wall
• Actually changes the shape in order to focus the light
• Refract the light onto the back wall —> onto the retina of your eyeball

Question 8

Astigmatism

Answer 8

• eyeball is lumpy
  
  • Not too long, not too short —> bumpy
  • projecting onto that back wall retina has a bit of trouble because it’s going to be projecting at different spots on there
  • Usually we can have the circumstances of corrective lenses to help us out so it can refract, do the job a little bit better compared to our lens
  • Refracting it in multiple different locations because of that essentially lumpy aspect

Question 9

Visual field

Answer 9

• Right visual field —> gets projected to your back left wall
• Left visual field —> gets projected to your back right wall —> right retina
• Works bc your eyeball also has a top and a bottom
• Auditorium here is actually getting a projector to the ceiling of eyeball —> getting projected to your bottom
• How your visual field comes into your retina: gets projected in an opposing manner —> everything gets switched —> your brain does a whole bunch of stuff in order to compensate
• Never believe anything coming into your eye because it’s already getting projected in opposing fashion and yet you don’t perceive it as that
• When it activates your visual receptors —> have transduction happen
• Photo receptors are at retina —> quite large (yellow area)
• As it goes towards like what your cheek area —> your lateral wall goes all the way
• there’s the back wall, but also on this medial side closest to your nose —> where all our visual receptors are at
• A big piece of area with this whole vitreous humour —> gel-like substance that fills the space between the lens and the retina + makes up the majority of your eyeball room

Question 10

Three main layers in Retina

Answer 10

• photo receptors —> our visual receptors
  
  • furthest away from how light was coming into your eye
• bipolar cells —> two processes coming off of it —> talk to some ganglion cells
• Ganglion cells —> true neurons of our visual pathway
• If we’re following light —> goes through the cornea —> goes through the pupil —> goes through the lens —> it goes through your vitreous humour —> go through your ganglion cells and your bipolar cells before it can activate the photoreceptors

Question 11

Optic

Answer 11

• Retina —> where we have all those photo receptors
• Lens —> no photo receptors
• Optic disc —> no photo receptors
  • Optic nerve coming out of that location
  • Also see blood vessels coming in and out of that location
  • Optic disc —> bright area on the right —> convergence of all those blood vessels helping us out with brain nutrients + gases to that area
• If location where there are no photo receptors —> if light were to shine on your optic disc —> would not perceive it —> your natural blind spot

Question 12

Glaucoma

Answer 12

• usually observed with regards to high correlation with cardiovascular disease, high blood pressure
• optic disc —> place where blood vessels coming in out of that location
• increased pressure —> increased pressure around this area —> increased pressure on the entire eyeball, including actually physically encroaching onto your optic nerve
• Outside peripheral of your visual field start to disappear
• Damage visual field usually can’t be recovered because it is actual damage to axons of neurons
• Axons getting damaged —> if surrounded by Glia —> can have a degree of recovery but not always the case

Question 13

Fovea

Answer 13

• the very central part of your retina
• little divot —> a little bit thinner in that location
• If you want to see something in detail —> you will always try to get light to hit this particular part of your eyeball
• Light reflecting off me —> going to go straight to your fovea when you’re doing that
• it’s a little divot —> bc the ratio of communication between your photo receptors, your bipolar cells, and your ganglion cells —> one to one to one
• Have a direct line of communication between your fovea and your brain —> why you can see things in a greater amount of detail
• Should have two —> all at the back wall and that central part of your retina