L13-Vision Flashcards

1
Q

Why are planktons and plants better adapted when they can sense light?

A

They can optimise sun exposure- photosynthesis.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

If animals have eyes, why must they be a big advantage?

A
  • Eyes are very metabolically expensive.

- Only have them f they’re really worth it.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What happens to Mexican blind cavefish’s eyes?

A
  • They develop eyes embryologically

- then reabsorb them because they cost too much energy. (probably evolutionary to develop them)..

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What do all eyes use to detect light?

A

All use the same basic molecule to detect light- opsins.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are the differences in different eyes?

A
  • Many different solutions for lenses to focus light.

- Inverse and everse retinas.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What’s the similar developmental genes in eyes?

A

Pax-6.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

In vertebrates, where is the retina derived from?

A
  • The ectoderm/ neural tube.

- It’s an extension of the brain.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What does the cornea do?

A

Greatest refracting power in the eye.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What does the lens do?

A

Accommodate the refracting power. Change shape for refracting power.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Where does the light hit at the back of the eye?

A

the fovea

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Gross structure of the vertebrate eye

A

look at diagram!

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What’s the laminar structure of the retina?

A
Pigment epithelium
rods + cones
Muller cells
horizontal cells
  \+ bipolar cells
amacrine cells
ganglion cells
nerve fibre layer
inner limiting membrane
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Which way is the arrow drawn in the lamina?

A

From the “excitable” cells, nerve fibres towards the photo-receptors, rods + cones.
Towards the detection of light.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What’s the order of cells along the arrow from the Ganglion cells?

A
Ganglion cells
Amacrine cells
Bipolar cells
Horizontal cells
Muller cells
Rods + cones photoreceptor cells
Retinal pigment epithelium
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What’s the RPE?

A

Retinal pigment epithelia
— pigmented layer at the back of the retina.
‘wraps’ outer segment of rods + cones

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the RPE importance in recycling?

A

Retinaldehyde- an essential co-factor of opsins

17
Q

what is tapetum lucidum (eye shine) ?

A

The layer just behind the RPE.

light absorption and/ or reflection

18
Q

In the retinal pigment cells what do melanin granules and tapetum do?

A

Melanin granules = absorb light

Tapetum = reflects light

19
Q

What are the steps in phototransduction in rods and cones?

A
  1. Photon of light
  2. Conformational change in rhodopsin molecule
  3. Activation of transducing
  4. Activation of phosphodresterase
  5. Reduction in cGMP
  6. Closure of sodium channels—-
    —presence of stimulant = hyperpolarisation.
    Very odd.
20
Q

What is odd about phototransduction in rods and cones?

A
  • Presence of stimulant = hyperpolarisation
  • Usually in cells —depolarisation.
  • In dark they are depolarised with Na channels open,
    in the light cGMP is reduced and Na channels close
    Opposite of usual.
21
Q

What does membrane depolarisation in rods and cones do?

A

Glutamate release.

22
Q

In primates how much of the cortex is devoted to processing visual information?

A

More than 50%. Very important sense.

23
Q

What are 6 common defects in human vision?

A
1 - Refractive errors
2- Cataracts
3- Diabetic retinopathy
4- Glaucoma- damage to optic nerve
5- Genetic defects in proteins e.g. rhodopsin
6- Tropical diseases e.g. trichoma
24
Q

What is the invertebrate retina made up of?

A

Individual units - ommatidia

Information from all- integrated in the brain.

25
What do pigment cells do in invertebrates?
Prevent light scattering into other ommatidia.
26
What are the steps of phototransduction in invertebrates?
1. Photon of light 2. Conformational change in rhodopsin 3. Activation of Gq 4. Activation of phospholipase C 5. Phosphoinositide hydrolysis 6. Cation channels open 7. Depolarisation
27
What's the main difference in phototransduction between vertebrates and invertebrates?
Vertebrates- hyperpolarisation | Invertebrates- depolarisation
28
What do a small proportion of retinal ganglion cells contain?
An additional opsin different from rods and cones.-- | --- melanopsin
29
What does melanopsin do?
Measure levels of brightness important in unconscious light detection e.g. circadian rhythms, pupillary light reflex, body temp.
30
In response to light, what happens in ganglion cells?
1. Vertebrate --- Na channel closes. Hyperpolarisation. 2. Invertebrate ---Na channel opens. Depolarisation. GPCRS ---various responses.
31
What does vertebrate vision rely on?
- Rhodopsin - Transducin - Hyperpolarisation
32
What does invertebrate vision and melanopsin involve?
Depolarisation