Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

PHYL 2401 > The eye > Flashcards

The eye Flashcards

1
Q
  • Sclera
  • cornea
  • aqueous humour
  • iris and pupil
  • lens
  • ciliary muscle
  • vitreous humour
A

Sclera: white; around whole eye

Front: sclera gives way to cornea
- At front: aqueous humour

Behind this: iris (colour part) with a black hole (pupil)
•Black because no light coming out of it

Behind iris and pupil: lens (transparent)

Proteinaous structure: Sits on ciliary muscle

Rest of eye filled with vitreous humour

Back of eye: how we actually see: retina

Behind retina: dark structure: choroid
(Dark in humans: any light that gets in and doesn’t get absorbed by retina is absorbed by choroid)
-Stops light from bouncing around
- In many animals, choroid reflective (nocturnal animals)

Light not absorbed by retina
o Seeing light (no matter where from) is better than not seeing light

The back of retina: fovea: Fine focus

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

what gives rise to nerves and nerve axons which gather to form optic nerve

A

retina

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

major and minor blood supply

A

major: optic nerve blood vessels
minor: sclera blood vessels

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

the cornea

function and irrregular

A

Nerve ending: trigeminal nerve

Very sensitive to touch

Light coming in have to be bent 

2/3 of this process is done by cornea (lens only adjusts focus)

Front of cornea irregular: focusing messed up

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

The pupil

  • pinhole effect
A

Radial and circular muscles of iris control size

Pinhole effect
- Because of pinhole, light from one part of object only reaches on part of the eye (focusing)
- Distance of object from pinhole doesn’t matter
 Still get sharp image
 Depth of focus
- Smaller pupil = better focusing on back of the eye

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

The iris

A

Haemoglobin in blood is very red  contributes to eye colour

  • Eye colour very difficult to predict (even if genetics known)
  • Many complications in iris colour
  • Motion and level of attention can change size of pupil
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

The lens

A

Adjusts focus

Distant: Thin because being stretch out by zonule fibres (pulling it)

Near vision:
- Circular ciliary muscles contract which causes lens to relax

Only activating focusing power when looking at distant things  when lens get older, it gets rigid so can’t relax as easily so can’t see things in near vision (far-sightedness)

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

Accommodation based on distance

A

Distant: thin lens

Near: bending is done by making lens thicker (relaxed)

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

accommodation and vergence

A

As an object moves farther and closer, lens must change shape (accommodate) to maintain focus
o Ciliary muscles do this

Close object: eye converge (turn in)
o Degree of convergence used by brain to determine how far or clos object is
This is binocular depth cue

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

Cataract

A
  • Accommodation is lost: lens has fixed depth focus after surgery because not reconnected to zonule fibres
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Aqueous and vitreous humour

A
  • Called humour: body fluid

- Vitreous tension: experience effects as age

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

Aqueous humour and glaucoma
- IOP

  • Glaucoma
A

IOP: measured by pushing against front of eye (more ways to measure as well)

  • Measured by: high pressure associated with glaucoma
  • But there are a group of glaucoma patients that don’t have raised IOP

Glaucoma

  • Visual world starts to “shrink”
  • Most patients don’t realise anything is wrong until already lost a lot peripheral vision

If canals get locked, do surgery to make tiny hole to try and cause drainage (more procedures for glaucoma too)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

The Retina

A

Choroid absorbs most of the light
o So ophthalmic scope has to be very bright so can get some light to retina during eye exams

Fovea is in centre of macula
o Light accurately focused

Because blood vessels and nerves in optic disk, there is no retina
o We don’t notice blind spot because two blind spots are different (one eye fills in for the other)
o Also, brain fills in the image (compensates for missing area by blind spot)

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

Light

A

EM can be seen over huge range (gamma to microwaves)

We see 400nm to 700nm
o Restrictive
o Nobody can tell what anyone else sees (in terms of colour)

Wavelength gets longer, energy becomes lower
o A lot of animals can see beyond 400nm
o Not many can see past 700nm (can’t see low energy light)
o Humans don’t see past 400nm because of lens, fovea, retina structure

Find it very difficult to see in extreme light and in extreme lack of light
o This only applies if don’t allow time for adaptation
o Allow time for adaptation, can see better in these conditions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Retinal cells

A

Choroid absorbs light not use

Rods and cones detect light

Rods and cones to horizontal cells

Bipolar cells synapse from rods and cones to ganglion
oMultiple bipolar on one ganglion

Ganglion has axons that form optic nerve

Light has to hit all these neurons before it is seen by rods and cones

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

Retinal regions

A

Fovea is depression in macula

Within fovea, smaller depression called foveola

Outside macula: periphery
o Many rods, few cones
o A lot of convergence

17
Q

Fovea vs Foveola

A

Fovea: Mainly cones
Foveola:
- Only cones
- Very thin cones packed close together
- Camera with a lot of pixels (analogous to pixels in camera)
- Each cone in foveola have direct connection to brain

18
Q

Rods and cones

A

-impossible to make rod more sensitive than it already it

Cones are less sensitive -> need more light t see colour

at night mainly use rods.

19
Q

Rods

A

-Cilium is greatly enlarged to form rod structure

End of rod: disks

  • Made of membrane
  • First 10-20 disks formed by membrane invaginations
  • Later, separate disks
  • Light passes through cell body and into disk region to be absorbed by rhodopsin

Have a lot of disks so that is photon passes first without being absorbed, next disk will absorb it or next will, etc.

20
Q

Cones

A

All of the disks are invaginations of outside membranes

In some animals (NOT HUMANS) find oil droplets full of brightly coloured pigments
- Birds and some amphibians or reptiles: have these to enhance colour vision

21
Q

Rhodopsin turnover

A

Band of radioactivity appears at beginning of rod until it gets to choroid and is chewed up

Rhodopsin doesn’t move around in eye

If disks aren’t degraded, get build up of disks

Accumulation of disk

  • Rod or cone degradation
  • And slowly loss of vision
22
Q

Rhodopsin structure

A

Two things make it up: opsin and retinal
- Retinal is the molecule that actually absorbs light

Retinal is constant, opsins are variable

Retinal surrounded by amino acids (opsins) which shifts vibration frequencies of the double bonds in retinal which gives different light absorption wavelength

We absorb 4 different colours
- Human females may see colours better because has two X chromosomes and some opsins are on X which increases ability to see colour (may be able to see more colours)

Butterflies: have 8-9 opsins (see a lot of colours)

Some animals have less opsins

23
Q

Transduction in rods

A

Rhodopsin absorbs light, forms metarhodopsin to cGMP

Normally enough cGMP in resting rod for Na+ to enter but when light comes through closes sodium channels and cells hyperpolarise
- In Human rods, stimulus (light) causes hyperpolarising change

24
Q

Ion currents in rods

A

Calcium concentration inside goes up when cell stimulate

Have Na+/Ca2+ exchanger which extrudes Ca2+ that comes in which Na+

When light falls, cell hyperpolarises and changes amount of calcium and this change causes adaptation

25
Q

Light adaptation

A

A lot of rhodopsin being changed to metarhodopsin that amount of rhodopsin drops 1% of normal

Rods adapt better than cones
- Useful for night vision

Cones faster than rods

26
Q

Time course to adaptation

A

When enter room, need quite a bright light to adapt

Need much smaller amount of light as time passes

When go into dark room, very hard to see what’s going on but after a while when lights up, takes a couple of seconds to adapt to light after dark

27
Q

Temporal resolution of vision
How fast can we see?

practical effect: movies

A

Increase speed of flash, see continuous light after a while

As light gets bright, can see separate flashes even if flashes very fast

Practical effect: movies

  • Camera takes pictures of a series of pictures and figure out how fast to play picture to make it look like a moving film
  • 50 frames per second is when this starts to look like a moving film instead of flickering images

PHYL 2401 (1 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions