Brainscape's Knowledge GenomeTM

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


See full index

2ND YEAR SYSTEMS: Neuro > How we see > Flashcards

How we see Flashcards

1
Q

what wavelengths of light will our retina respond to?

A

Our retina will only respond to images of light rays between 400-800 nanometres

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

How many layers does the retina have?

A

10

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

Where do the rods/cones sit within the retina layers?

A

they sit pretty deep in the outermost layer called the outer segment

light has to travel through all the layers to hit them

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

what contains rods/cones

A

discs/lamellae contain photoreceptors (rods and cones)

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

what is each lamellae made up of?

A

a cell membrane

integrated into this membrane is the visual pigment (proteins) rhodopsin in rods and cone opsins

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

how many types of cones are there? and what are they called?

A

3
S, M and L
Short, medium (green) and long (red) wavelength types

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

What is the only difference between rods and cones?

A

they respond to different wavelengths of light

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

What is chromophore formed from?

A

dietary vitamin A

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

What happens when light hits rod?

A

11-cis retinal (vit A compound) changes from cis to trans - alters shape

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

what is rhodopsin made up of? (2)

A

opsin and 11-cis retinal (helical protein)

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

when vit A changes shape what happens to rhodopsin?

A

rhodopsin splits and bleaches as not all trans retinal can fit in the opsin

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

Bleaching of the visual pigment results in what?

A

phototransduction cascade

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

What role does Vitamin A play in the visual pigment?

A

visual pigment regeneration

To correct the cascade after 1 photon of light we need energy (ATP) – channel opens again and ready for business again. Need to get Vit A to convert back to normal shape and latch onto rhodopsin so that rhodopsin is ready for next photon of light

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

Describe the phototransduction cascade

A

When light hits vit A – changes from cis to trans

Vit A changing shape results in a cascade of reactions - these spread through until they meet an optic nerve cell

ultimately causes hyperpolarisation (Na+ channels close) and AP produced in optic nerve cell

Then pigment epithelial cells convert trans –retinol (vit A) back to cis-retinol this is then transported back to rod/cone to reform opsin

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

what is different about photoreceptor cells in comparison to other cells in the body

A

photoreceptor cells are, at rest (in the dark), kept in a depolarised state by open Na+/Ca+ channels (not closed like normal)

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

What are pigment epithelial cells and what is their function?

A

Cells in the deepest part of the retinal layer

All-trans retinol taken up here and converted back to cis retinol which can then go back to make rhodopsin

Want to absorb it so that it’s not bouncing back and making multiple images on the retina

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What happens to vitamin A along the regeneration pathway

A

At certain points along the way – lose a bit of Vit A which can’t be reincorporated into the regeneration process so we need to keep replenishing it through our diet

E.g Fish oil, carrots

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Vitamin A deficiency

A

any condition that affects vitamin A absorption will affect vision – (night) blindness.

Vitamin A is also essential for healthy epithelium. So conjunctiva and corneal epithelium are also abnormal.

can occur in conditions such as malnutrition, malabsorption syndromes such as coeliac disease, sprue (immune (allergic) reaction to gluten).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Clinical signs of vit A deficiency

A

Bitot’s spots in conjunctiva - silvery triangles

corneal ulceration

More serious is corneal melting which can progress to opacification

20
Q

What is refraction of light?

A

bending of light when it passes from one optical medium to another ie air to liquid

When light comes into your eye – in our eye there is transparent media – this helps to bend the light and the image you see forms on the retina

21
Q

What are the transparent parts of the eye?

A

cornea
Aqueous Humor
Lens
Vitreous Humor

22
Q

which parts don’t help bend light in the eye

A

Aqueous humor

Vitreous humor

23
Q

function of the choroid

A

provides retina with nutrition

24
Q

Why does light need to fall in the centre of the eye to work?

A

Light needs to fall in the centre in order to hit the cornea then it will pass through the AH, lens and VH which are all transparent – light will travel and bend

25
Q

What happens with your eyes when an object is close up

A

only divergent (less parallel) rays form on cornea so the eye has to work much harder to bend the light rays in order to form image on retina – need to make lens more biconvex (by using ciliaris muscle) so you can bend light more and image still forms on retina

26
Q

What happens with your eyes when an object is far away

A

light rays are more parallel so the eye has to work a little (but not as much as if up close) for image to be formed

27
Q

which part of the eye can change its power?

A

the lens - you can make it more or less powerful through movement of the ciliaris muscle

28
Q

Which is the most powerful ‘bender’ of light?

A

the cornea however its power can’t be altered, it is static

29
Q

Which 2 parts of the eye do help bend light

A

cornea

lens

30
Q

What is accommodation

A

The process of increasing the power of eye (lens) in order to see/focus better from distant objects to close objects

31
Q

What are the 3 things that happen simultaneously during accommodation?

A

Lens changes shape (becomes thicker & more spherical)

Pupil constricts

Eyes converge

32
Q

How does the lens thicken?

A

Ciliary body contraction (parasympathetic - by oculomotor nerve) and suspensory ligament relax - lens is no longer under stretch - causes lens to become thicker & more spherical

thicker lens = more powerful and better focus up close

33
Q

How do pupils constrict during accommodation

A

To sharpen focus the pupil constricts to allow only a few rays (those from the object) to pass through so you can focus up close

Pupillary constrictor (sphincter pupillae) is a concentric muscle around the border of the pupil which gets parasympathetic innervation.

34
Q

Why do your eyes converge during accommodation

A

When focussing on an object up close, our eyes have to turn in to look at the object = convergence.

We use our medial rectus muscles of both eyes to converge. (Oculomotor of both sides)

35
Q

Name some refractive errors (4)

A

Myopia – short-sightedness

Hyperopia – long-sightedness

Astigmatism – non-spherical curvature of cornea (or lens)

Presbyopia – long-sightedness of old age

36
Q

what is perfect vision called?

A

emmetropia

37
Q

What is myopia?

A

Short sightedness

Usually because the eyeball is too long so image forms in front of the retina

Far away – hazy image because it doesn’t reach the retina and forms before it

Close up – eye is more powerful – no accommodative power needed

38
Q

Symptoms of myopia

A

Headaches, Complain of not being able to see board/ distant objects.

Infants & preverbal children - divergent squint

Toddlers - loss of interest in sports/people. More interest in books, pictures (can see well close up)

Teachers may notice child losing interest in class.

39
Q

Myopia correction

A

Glasses - diverge light rays so image forms on retina - irritating as smaller field of vision

Contacts

Laser eye surgery

40
Q

What is Hyperopia

A

far sightedness

Eyeball is too short or cornea and lens are too flat
Image forms behind the retina - close up looks hazy, far away objects appear clear

person starts to use accommodative power naturally to see far off things that they should normally see without this

for close up they use more and more power until ultimately, their power is all used up so they can’t see close up

41
Q

Hyperopia symptoms

A

Symptoms of eyestrain after reading/ working on the computer in a young individual.

Convergent squint in children/ toddlers – needs immediate correction with glasses/lenses to preserve vision in both eyes and prevent a “lazy eye”.

42
Q

Correction of hyperopia

A

Biconvex glasses alleviates use of glasses for focusing distant objects and ‘rests’ the accomodative power

Contact lenses

Laser Eye surgery

43
Q

What is Astigmatism?

A

unequal curvature of the eye
close and distant objects appear hazy - blurry vision due to having more than one image forming and can form in front or behind the retina - any combination

44
Q

How do we correct astigmatism

A

need special glasses – called cylindrical glasses (which are curved in only one direction).

Laser eye surgery can also be used to correct the defect.

Need special contact lenses called toric lenses.

45
Q

What is presbyopia

A

long-sightedness of old age (blurry up close)

Lens becomes more rigid with age (starts 40-49) – even if muscles contracting lens isn’t moving much

corrected by reading glasses

2ND YEAR SYSTEMS: Neuro (32 decks)

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