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Physiology > The Eye (I) > Flashcards

The Eye (I) Flashcards

1
Q

What does wavelengths of light allow

A

Detection of colour

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2
Q

What does the cornea do

A

Refracts light

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3
Q

What is behind the cornea and what is it controlled by

A

Pupil - allows light in

Controlled by iris muscles (circular and radial)

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4
Q

What area of the eye allows focus onto retina in close or far vision

A

Lens

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5
Q

How does lens change shape for close or far vision

A

Ciliary muscles which attach to lens by zonulas

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6
Q

How is the image reflected on the retina

A

Inverted and reversed

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7
Q

What does lens accommodation mean

A

Ability for lens to fatten or flatten depending on close or far vision through its ciliary muscles

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8
Q

What is the lens and focal length like in distant vision (helped by the SNS)

A

Lens is flattened (ciliary muscles are relaxed)

Focal length is long

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9
Q

What happens for close vision in lens accommodation

A

Lens fattens/widens via ciliary muscle contraction and zonula slackening (via PNS)

Focal length is shorter (via PNS)

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10
Q

Which area is there the blind spot (no photoreceptors)

A

Optic disc

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11
Q

Fovea is in the retina, which photoreceptors does it have for high acuity / resolution and colour

A

Cone receptors

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12
Q

What does light pass through first in retina

A

Blood vessels and nerve fibres

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13
Q

Explain the structure of retina from back of it

A 
Pigment epithelium 
Rods/cones 
Bipolar cells
Ganglion cells
Blood vessels / nerve fibres
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14
Q

Which pigment do pigment epithelium make at retina and why

A

Melanin to absorb light

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15
Q

Which cells lay horizontally in retina

A

Horizontal and amacrine cells

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16
Q

Fovea only contain cone cells, why does it have high visual acuity

A

Light doesn’t have to pass through blood or nerve fibres first, retina pushes back to expose cone cells in fovea

17
Q

Which type of light are rod cells for (mainly highest in retina)

A

Scotopic light - low light levels

18
Q

Why are rods called contrast

A

Can’t detect colour only black and white in low intensity light eg darkness (Scotopic vision)

19
Q

Where does rhodopsin pigment in rods bleach / inactivate

A

High intensity light

20
Q

What are the 3 types of fovea cone cells

A

Low medium and high wavelength cells

21
Q

What is advantage of cone cells

A

High resolution/ acuity

Colour vision

22
Q

What is the vision called using cone cells

A

Photopic vision

23
Q

Where is photopigment produced in cone and rod cells eg rhodopsin

A

Membranous discs in the cells (lipid bilayer)

24
Q

What does dark adaptation mean

A

When someone goes from light to dark, they become blind for seconds because rhodopsin is still bleached and cone cells are inactivated in dark

This quickly goes back up when rod cells become active again = dark adaptation

25
Q

What is the colour vision theory of cone cells called

A

Trichromatic theory

26
Q

What does the trichromatic theory mean

A

The 3 diff wavelength sensitive cone cells at each wavelength have a specific pattern of outputs which make up a colour

27
Q

Why are red LED lights needed in dark

A

Rod cells are low sensitive at that wavelength

28
Q

How is light transduced into signals

A

Photopigments from the membranous discs

29
Q

How many pigments are in cones

A

3 diff ones

30
Q

What makes up rhodopsin

A

Opsin protein and 11 CIS retinal

31
Q

When active (in dark ) what happens to opsin and 11 CIs retinal

A

they are joined together

32
Q

What happens to rhodopsin if rods exposed to light

A

Bleached

Opsin moves away from 11 CIs retinal

33
Q

In the dark, what are there high levels of at rod cells and why does this allow a high enough membrane potential

A

Cgmp

Cgmp allows opening of na channels so na moves into rod cells whilst K moves out keeping it at -40mv

34
Q

Which Nt is released from rod cells in dark when na channels still open due to cgmp

A

Glutamate

35
Q

What gcpr is activated when rhodopsin bleaches in light

A

Transducin

36
Q

What does transducin do to cause hyperpolarisation at rod cells in the light chasing no Nt release

A

Lowers cgmp so na channels close

K keeps leaving the cell causing -70 hyperpolarisation

This stops nt glutamate release (inactive rods)

Physiology (31 decks)

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