Brainscape's Knowledge GenomeTM

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


See full index

Physilogy > Physiology Of Vision > Flashcards

Physiology Of Vision Flashcards

1
Q

What is cornea

A

Dome-shaped window which provides the majority of the focusing power of the eye. It is clear and avascular and continuous with the sclera.

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

What is iris

A

Thin, elastic, circular structure responsible for controlling the diameter and size of the pupil and thus the amount of light reaching the retina. The iris determines eye colour.

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

What is lens

A

Crystalline structure which aids focusing of light onto the retina. Its curvature is altered and controlled by the cilliary muscles and the zonule fibres. Clouding of the lens causes cataracts.

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

Describe aqeous humour

A

Transparent gel like fluid which fills the anterior part of the eye between the lens and the cornea. It is formed by the ciliary body and drains via the trabecular meshwork. It maintains intraocular pressure (IOP), nourishes and removes debris from the avascular anterior segments of the eye.

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

How is glaucoma caused?

A

Glaucoma (open angle glaucoma) is caused by an increase in IOP commonly caused by degeneration of the trabecular meshwork reducing drainage of the aqueous humor.
Ciliary body Zonule fibres

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

What is sclera

A

Fibrous white opaque connective tissue layer covering 5/6 of the eye ball. Continuous with the transparent cornea. Both the sclera and cornea are made of Type 1 collagen.

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

What is choroid

A

Vascular connective tissue layer. Contains melanin pigment and nourishes outer 1/3 of the retina. Continuous with the ciliary body.

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

What is retina

A

Light sensing layer composed of the retinal pigment epithelium and the neural retina.

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

What is vitreous humor

A

Transparent gel which provides structure to the eyeball.

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

How is light passed into eye

A

Light passes through all the neural retinal cells to reach the photoreceptors at the back of the retina.

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

How is light focused in eye

A

Light is focused by the cornea and the lens and then passes through the vitreous humor to the retina.

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

What are the two types of photoreceptors in retina

A

Cones – colour system – daylight.
Rods – no colour – low light levels

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

Where does process of absorption occur?

A

Process of absorption occurs in the outer segments of the photoreceptors

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

What does outer segment contain of photoreceptors?

A

The outer segment contains a stack of membranous disks which contain the light sensitive photopigments.

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

What is the difference in appearance of rods and cones?

A

Rod photoreceptors have a long, cylindrical outer segment containing many disks, whereas cones have a short, tapering outer segment with few membranous disks.

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

What does photoreceptors do?

A

Photoreceptors transduce light energy into changes in membrane potential

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

What are the retinal cells?

A

Horizontal, bipolar, amacrine and ganglion cells

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

What do the Horizontal, bipolar, amacrine and ganglion cells do?

A

pre-processing’ before sending the visual information through the optic nerve.

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

Each photoreceptor is in synaptic contact with which two types of retinal neurones?

A

bipolar cells and horizontal cells.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What do bipolar cells do?

A

Bipolar cells create the direct pathway from photoreceptors to ganglion cells.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What do horizontal cells do?

A

Horizontal cells feed information laterally in the outer plexiform layer to influence neighbouring cells.

22
Q

What do amacrine cells do?

A

Amacrine cells control and modulate the majority of the inputs to the retinal ganglion cells and the ganglion cell responses.

23
Q

What are the major glial cells of retina?

A

Müller cells

24
Q

Where are Müller cells located?

A

They are located in the neuronal retina and span its entire depth.

25
Q

Role of muller cells

A

Müller cells ensheath all retinal neurons and contribute significantly in mediating their functions and stability.

26
Q

What is the pigment in rods called?

A

Rhodopsin

27
Q

What are the 3 types of opsin in cones?

A

•
•
The pigment in all rods is called rhodopsin (rod – opsin).
In each cone there is one of three types of opsins; red, green and blue. Each cone opsin has a different spectral sensitivity:

28
Q

How is colour perception determined in cones?

A

The pigment in all rods is called rhodopsin (rod – opsin).
In each cone there is one of three types of opsins; red, green and blue. Each cone opsin has a different spectral sensitivity:
Colour perception is determined by the relative contribution of the blue, green and red cones to the retinal signal.

29
Q

What is colour blindness?

A

Colour blindness or colour deficiency is the inability or decreased ability to see colour or perceive colour differences

30
Q

What is achromatopsia

A

Total colour blindness
This is rare (3/100,000) and is caused by genetic mutations which result in only rod photoreceptors being functional. Affected patients see no colour but also have poor vision in bright light due to the sensitivity of the rod photoreceptors (one photon activates a response). They also have poor visual acuity due to lack of cones.

31
Q

What is dichromacy?

A

One of the three basic colour mechanisms is not functioning.

32
Q

Which dichromacy is x linked?

A

Red-green colour blindness”
Deuteranopia (mutation of green opsin) Protanopia (mutation of red opsin)

33
Q

What is blue yellow colour blindness called?

A

Tritanopia

34
Q

What are males mostly affected by in colour blindness.

A

affected by red-green deficiency due to X-linked inheritance. The red and green opsin genes are on the X-chromosome.

35
Q

What percentage of men have mutant green opsin ?

A

5%

36
Q

What percentage of men have mutated red opsin?

A

1%

37
Q

What is phototransduction?

A

Phototransduction is the process by which light is converted into electrical signals in the rod and cone cells.

38
Q

What are the photo pigment protein in photoreceptor outer segments?
Phototransduction pathway

A
  • protein coupled receptors which are chemically attached to a vitamin A derived chromophore called 11-cis retinal.
39
Q

What happens to the G- protein coupled receptors which are chemically attached to a vitamin A derived chromophore called 11-cis retinal. ? Phototransduction pathway

A

. Light photons strike this chromophore and cause a conformational change to all-trans retinal. This isomerization triggers the visual process by activating a signal transduction cascade.

40
Q

Describe visual cycle

A

A photon of light activates the 11-cis-retinal to change it to all-trans–retinal.
All-trans-retinal is not photosensitive so the opsin must release this chromophore and replace it with more 11-cis-retinal. This process is called the visual cycle.

41
Q

What would happen if the proteins in visual cycle was mutated?

A

Inherited blindness

42
Q

What is a vitamin a derivative?

A

11-cis-retinal is a vitamin A derivative!

43
Q

What is 11-cis-retinal depletion?

A

See light brighter than normally is

44
Q

Describe signal transduction in photoreceptors

A
  1. Guanosine diphosphate (GDP)-bound inactive transducin will exchange GDP for guanosine triphosphate (GTP) following interaction with activated rhodopsin.
  2. The activated GTP-bound α-subunit of transducin dissociates and activates cyclic guanosine monophosphate (cGMP) phosphodiesterase (PDE).
  3. PDE hydrolyzes cGMP to 5’GMP. The result is decreased levels of cGMP in the cytoplasm. This causes the closing of cGMP-gated ion channels leading to membrane hyperpolarization.
  4. In photoreceptors, the neurotransmitters are released in depolarized membranes (dark light).
45
Q

Why can activation of single rhodopsin by single photon be sufficient to cause a significant change in membrane conductance?

A

This is possible due to amplification steps present in the transduction cascade.
A single photoactivated rhodopsin catalyses the activation of 500 transducin molecules.

46
Q

What are the structures that transmit the signals received by the retina to the visual cortex for processing and decoding

A

retina, optic nerves, optic chiasm, optic tracts, lateral geniculate nuclei, optic radiations and the visual cortex in the occipital lobe.

47
Q

What is the first region of visual processing in cortex?

A

Striate cortex or V1

48
Q

What are the 2 cortical streams of visual processing?

A

Striate cortex towards
– parietal lobe: visual motion.
Striate cortex towards temporal lobe: recognition of objects.

49
Q

What is lateral inhibition?

A

The capacity of excited neurons to reduce the activity of their neighbours

50
Q

How is direct input given by receptive field?

A

DIRECT input of photoreceptor to bipolar cell from receptive field centre

51
Q

How is indirect input from receptive field given?

A

INDIRECT input from photoreceptor to bipolar cells via horizontal cells from receptive field surround

Physilogy (1 decks)

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