Vision

Question 1

What does the outer fibrous layer of they eye have?

Answer 1

Has a non-sketchy sclera around the outside

Question 2

What happens to the sclera at the front of the eye?

Answer 2

Becomes the non-transparent cornea the front of they eye

Question 3

What is the cornea at the front of the eye inflated by?

Answer 3

Inflated by fluid

Question 4

What humor is nicely hydrated and where is it located?

Answer 4

vitreous humor is nicely hydrated and is located at the back

Question 5

What allows cornea to bend light rays?

Answer 5

Cornea is highly curved so bends light rays

Question 6

What does the lens do?

Answer 6

Lens inside bends light further

Question 7

What is the lens suspended on the ends of?

Answer 7

Suspended on the ends of suspensory ligaments from the cillary body

Question 8

What does the cillary body include and what can this do?

Answer 8

Cillary body includes a muscle which can contract and relax making the lens fatter or flatter

Question 9

What does a fatter lens do to light?

Answer 9

Fatter lens refracts light more

Question 10

What does the iris control?

Answer 10

Iris controls central size of pupil and amount of light entering eye

Question 11

What is the cornea primarily responsible for?

Answer 11

Primarily responsible for focusing light rays

Question 12

What does a lens additionally provide?

Answer 12

lens provide additional variable fine focus

Question 13

What is the job of the pupil?

Answer 13

Pupils job is to stay as small as possible to improve focus

Question 14

Why is the retinal pigment epithelium an important structure?

Answer 14

Important structure as it keeps the neural retinal alive

Question 15

What is the neural retina?

Answer 15

Neural retina is an outpost of the brain and generated from the neural tube

Question 16

What does the neural retina contain and what does this link?

Answer 16

Neural retina contains a neural circuit which links the photo receptors to the retinal ganglion cells

Question 17

What is the primary visual pathway?

Answer 17

• Axons from the retinal ganglion cells project back via the optic nerve
• The 2 optic nerves meet at the optic chiasm
• The optic nerves run along the optic tract which dives up the brain
• Many of the axons have branches that extend to the brain stem
• Main branch goes to the lateral geniculate nucleus in the thalamus
• Relay cells are activated in the LGN that carry signals to the primary visual cortex

Question 18

What are rod receptors for?

Answer 18

For night vision

Question 19

What are cone receptors for?

Answer 19

For day vision

Question 20

What is the structure of cone photoreceptors?

Answer 20

• Outer segment involves membrane discs

- Inner segment involves nucleus

Question 21

What is the membrane potential of cone photoreceptors?

Answer 21

-45mV

Question 22

Why are cone photoreceptors polarised?

Answer 22

• They’re polarised because they have K+ channels that are leaking out
• Also have channels in there outer-segments that leak Na+ in and these are open by default

Question 23

What happens if light over outersegment gets brighter?

Answer 23

If light over outer-segment gets brighter, the cell hyperpolarises reducing release of glutamate

Question 24

What happens if light over outersegment gets darker?

Answer 24

If light over outersefment goes darker, the cells depolarise and more Na+ channels open and more release of glutamate

Question 25

Where is opsin present?

Answer 25

Opsin present on membrane discs in outer segment

Question 26

What is the protein component of photopigment?

Answer 26

Opsin

Question 27

What is the non protein component of photo pigment?

Answer 27

Retinal

Question 28

What are the 2 components that photopigment is made up of?

Answer 28

- Opsin | - retinal

Question 29

Steps involved in the initiation of light response in transduction

Answer 29

11-cis C bind is fairly unstable in retinal - When light strikes the retinal, it ruptures that bond and when the bond reforms it forms in the trans configuration - All trans retinal acts an agonist on a GPCR - Leads to the activation of G proteins which activate enzymes that breakdown cGMP - This allows Na+ to close

Question 30

Steps involved in the termination of response in transduction

Answer 30

- The opsin gets capped off by enzymes which causes trans retinal to go away - Opsin stops activating protein and stops activating enzymes - Enzymes form cGMP - 11 cis retinal then binds to opsin again

Question 31

What does loss of peripheral vision occur due to?

Answer 31

Occurs due to glaucoma, retinitis pigmentosa

Question 32

What happens if you lose your fovia?

Answer 32

You are registered blind

Question 33

What do photoreceptors communicate via to the ganglion cells?

Answer 33

Photoreceptors communicate via bipolar cells to the ganglion cells

Question 34

How do bipolar cells gather information and why is this done so?

Answer 34

Bipolar cells gather information through a whole pool of photoreceptors before passing it on to the ganglion cells so there is convergence in the pathway

Question 35

What does convergence increase and what does this mean?

Answer 35

Convergence increases pixel size therefore that's why peripheral vision is more blind

Question 36

Why don't blood vessels cross the fovea?

Answer 36

Blood vessels don't cross fovea because that's where the foveal pit is

Question 37

What types of images do you get at the foveal pit and why?

Answer 37

You get high detailed images at the pit because you can get good focus on the image

Question 38

What cones are in the foveal pit?

Answer 38

Only red and green cones in this area

Question 39

What is the image inverted by and so what does this mean?

Answer 39

Image in inverted by the optics | -So left side of the image found on the right side of both retinae

Question 40

What do axons from nasal retina do?

Answer 40

Axons from nasal retina swap sides therefore right side of both retinae go to the right side of the brain

Question 41

What is the image mapped on to?

Answer 41

Image is mapped on to the LGN and cortex with expanded central regions of the image

Question 42

What do the axons form in the LGN and cortex?

Answer 42

Axons form a retinotopic map in the LGN and cortex with the map for the 2 eyes in register

Question 43

What does the retinal ganglion cells report?

Answer 43

Report changes in illumination form one location to another

Question 44

What happens if theirs a change in brightness causing the excitation of a ganglion cell?

Answer 44

If there's a change in brightness causing the excitation of a ganglion cell, then information from excited cones will be fed through an inhibitory interneuron and they'll inhibit that ganglion cell -This means its not responding to absolute illumination, its the difference between brightness of the center vs the surroundings