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VMS 1008 > Physiology of vision > Flashcards

Physiology of vision Flashcards

1
Q

What are Ciliary bodies?

A

thickened anterior parts of the choroid, contain circular longitudinal muscle fibres , produce aqueous humour

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2
Q

What is the lens?

A

The adjustable focus, mediated by ciliary bodies

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3
Q

What is the iris?

A

Pigmented and opaque contains constrictors and dilaters

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4
Q

What is the vitreous humour?

A

A gelatinous substance between the lens and retina

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5
Q

What is the aqueous humour?

A

Clear liquid that nourishes the cornea and lens

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6
Q

What is accommodation?

A

the process by which the curvature of the lens is increased in order to focus on a near object

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7
Q

What is the principle focal distance?

A

The distance between the lens and the principle focus

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8
Q

Dioptres

A

Unit of the refractive power of the lens measured in metres

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9
Q

What happens when you increase the curvature of the lens?

A

It brings the focal point forward

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10
Q

What happens when the ciliary muscles contract?

A

Tension is released on the zonulas, therefore causing the lens to become more rounded

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11
Q

What does the iris control?

A

The quantity of light entering the eye

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12
Q

What does the vertical slit in a pupil do?

A

enhances distance judgement in brighter light

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13
Q

What is the sclera?

A

Outer layer of tough connective tissue which merges with the cornea

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14
Q

What is the cornea?

A

Transparent layer at the front, for physical protection, refraction of light and it is highly sensitive

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15
Q

What is the choroid?

A

Vascularised middle layer

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16
Q

What is the retina?

A

innermost layer that contains sensory cells and neurons

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17
Q

What are the two types of cell found in the retina?

A

Rods and Cones

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18
Q

Which layer contains the rods and cones in the retina?

A

The outermost layer

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19
Q

Which layer in the retina contains the ganglion cells?

A

The innermost layer

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20
Q

What are the interneuron cell types that the middle layer contains?

A

Bipolar cells, Horizontal cells and Amacrine cells

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21
Q

What is the optic disc?

A

The point where the optic nerve leaves the eye and blood vessels enter

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22
Q

What is the macula lutea?

A

A yellowish area near the posterior pole. It marks
the location of the fovea centralis

23
Q

What is the fovea centralis?

A

thin, rod free and cone packed area that contains no blood vessels

24
Q

What is the tapetum lucidum?

A

A layer that sits behind the retina that helps to reflect more light to the photoreceptors

25
Q

What are saccadic eye movements?

A

Rapid, taking many screenshots which the brain can then interpret as a stable image

26
Q

What are slow eye movements?

A

keeping a fixed visual point when the head moves

27
Q

What is the physiological nystagmus?

A

When image passes extent of eye movement range, a correcting saccade brings the eye back

28
Q

What is the Pathological nystagmus?

A

when the eye moves and saccades when the head is still indicating a problem with the vestibular system, horizontal indicate peripheral component problem, vertical indicates central problem

29
Q

What is retinal convergence?

A

When many rods converge on a single ganglion cell

30
Q

What do ganglion cells detect?

A

a difference in the light in the central and peripheral region rather than the intensity of the light

31
Q

What happens when the light spot is large enough to cover both the central and the periphery?

A

They signals cancel out

32
Q

What is a particle of radiation called?

A

a photon

33
Q

What is the inverse of a dioptre?

A

The principal focal distance

34
Q

What happens when you look at a near object?

A

The ciliary muscles contract and lens ligaments/ zonulas relax therefore the lens becomes more rounded

35
Q

What happens when you look at a far away object?

A

The ciliary muscles loosen therefore the zonulas contract flattening the lens

36
Q

What do the circular muscles in the iris do?

A

Constrict the iris, letting less light in

37
Q

What do the radial muscles in the iris do?

A

Dilate the iris, letting more light in

38
Q

What kind of muscle is the iris in mammals and birds/reptiles?

A

Smooth muscle in mammals and striated muscles in birds/reptiles

39
Q

What kind of ganglia cross over at the optic chiasm?

A

The medial ganglia, lateral ganglia do not cross over

40
Q

What does the geniculocalacrine tract do?

A

conducts sensory information to the visual cortex of the occipital lobe

41
Q

What are the two types of blood vessels in the fovea centralis and what are their functions?

A

Retinal vessels - supply the bipolar & ganglion
cells
* Choroid plexus - supplies the rods & cones

42
Q

What is the macula lutea?

A

yellowish area at the back of the eye/ near the posterior pole- it marks the location of the fovea centralis

43
Q

What is the function of the crystals of guanine/riboflavin in some cells?

A

reflects light enhancing vison

tapetum lucidum

44
Q

What is the function of some cells containing melanin?

A

absorbs melanin to improve visual acuity

45
Q

What is the purpose of herbivores having horizontal rectangular pupils?

A

It shields the eyes from high sunlight whilst maintaining panoramic vision

46
Q

What is the function of carnivores having horixontal pupils?

A

greater light control and enhanced distanced judgement

47
Q

What part of the eye is more abundant in cones?

A

The fovea centralis

48
Q

Which ganglia crosses over at the optic chiasm?

A

The nasal/medial ganglia
lateral ganglia does not cross over

49
Q

What is contra-lateral processing?

A

This means that both sides of the brain process
images from both eyes

50
Q

What is the geniculocalacrine tract?

A

connedcts the geniculocalacrine nucleus to the visual cortex of the occipital lobe

51
Q

What do the ganglion cells form?

A

The optic nerve

52
Q

What are the two different types of ganglion cells?

A
  • M-type for movement (magnus)
  • P-type for shape and detail (parvus)
53
Q

What are the two different types of ganglion cells?

A
  • M-type for movement (magnus)
  • P-type for shape and detail (parvus)
54
Q

How does the light cause hyperpolarisation?

A

Cgmp continually keeps the channels open so Na/Ca are continuously flowing in
Light converts 11-cis-retinal to 11-trans retinal
this activates a G protein which converts cGMP to GMP
this then closes the channels
hyperpolarisation occurs

VMS 1008 (20 decks)

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