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SF6: Organs of Special Senses and Endocrine Systems > W4 Physiology of Vision (part done) > Flashcards

W4 Physiology of Vision (part done) Flashcards

1
Q

a particle of electromagnetic radiation is called what?

A

a photon

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2
Q

do shorter or longer wavelengths of photons contain more energy?

A

shorter

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3
Q

vision is the perception of light, what is the visible spectrum?

A

400-700nm (based on human vision)

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4
Q

the vertebrate eye has a lens system, what does this aid?

A

focus light from objects in the environment onto the retina (where the sensory cells are located) and transmits information to the brain where the image is interpreted

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5
Q

what is visual acuity?

A

a measure of the ability of the eye to distinguish shapes and details of an object at a given distance

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6
Q

what are the ciliary bodies?

A

thickened anterior parts of the choroid, contain circular and longitudinal muscle fibers that produce aqueous humour

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7
Q

what is the iris?

A

it is pigmented and opaque and contains constrictors of the pupil (circular) and dilators of the pupil (radial)

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8
Q

what is vitreous humour?

A

a gelatinous substance between the lens and retina

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9
Q

what is aqueous humour?

A

a clear liquid that nourishes the cornea and lens

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10
Q

what is the filtration angle (schlemm’s canal)?

A

at the junction between the iris and cornea, which drains aqueous humour

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11
Q

what is the sclera?

A

part of the globe wall - the outer layer of tough connective tissue which merges with the cornea

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12
Q

what is the cornea?

A

the transparaent layer of the globe wall at the fron t that is for physical protection, refraction of light and is highly sensitive

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13
Q

what is the choroid?

A

the vascularised middle layer of the globe wall

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14
Q

what is the retina?

A

the innermost layer of the globe wall containing sensory cells and neurones

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15
Q

light rays refract when passing from one medium to another due to what?

A

difference in density

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16
Q

parallel light rays striking a biconvex lens are refracted to a point behind the lens called what?

A

the principle focus

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17
Q

what is refractive index?

A

the ratio between the speed of light in a vacuum and in the material

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18
Q

what is principle focal distance?

A

the distance between the lens and principle focus

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19
Q

what lenses diverge light and what lenses converge light?

A

biconcave = diverge light
biconvex = converge light

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20
Q

what is the unit of refractive power of a lens measured in meters?

A

dioptres (a dioptre is the reciprocal of the principle focal distance)

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21
Q

when is the distance between the lens and focal point the smallest?

A

when the light source is so far away that the light rays are traveling parallel to the lens

22
Q

the distance between the lens and the focal point decreases with increasing or decreasing curvature (convexity) of the lens?

A

increasing

23
Q

what is accommodation?

A

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

24
Q

when looking at a near object are the ciliary muscles relaxed or contracted?

A

they contract (distance between the edges of the ciliary bodies decrease and the lens ligaments relax)

25
Q

at rest objects objects closer than how many meters appear blurred?

A

6m

26
Q

the elastic lens is attached to the circular ciliary muscles by what?

A

the zonulas which is made of inelastic fibres

27
Q

when the ciliary muscles are relaxed what does the zonulas do?

A

zonulas pulls tight and keeps the lens flattened for distant vision

28
Q

when the ciliary muscles contract what happens to the zonulas?

A

the tension of the zonulas releases and the elastic lens returns to a more rounded shape for near vision

29
Q

what does the iris control?

A

the quantity of light entering the eye (smooth muscle in mammals and striated in birds and reptiles)

30
Q

what fibers dilate the pupil?

A

radial fibers

31
Q

what fibers constrict the pupil?

A

circular fibers

32
Q

some carnivores have vertical slit pupils, what does this allow for?

A

greater light control and enhances distance judgement in brighter light

33
Q

many herbivores have horizontal rectangular pupils, why is this?

A

shields eyes from high sunlight whilst maintaining panoramic vision to spot predators (eye rotates as head drops to keep pupil horizontal)

34
Q

what are the two types of ocular humours?

A

aqueous and vitreous

35
Q

where is aqueous humour produced and where does it drain into?

A

produced by the cells in ciliary body and drains into the venous plexus at the filtration angle (production and drainage must be balanced)

36
Q

is vitreous humour continuously replaced?

A

no

37
Q

vitreous humour is a gel-like mass of mostly water with a stroma of what?

A

transparent fibers

38
Q

what humours function is to retain globe shape?

A

vitreous

39
Q

the retina contains two sensory cell types, what are they?

A

rods - extremely sensitive (possible to see in low light (scotopic vison))
cones - convey colour vision

40
Q

which of the three layers of the retina consist of the rods and cones?

A

the outermost, closest to the choroid

41
Q

the innermost layer of the retina is nearest to the vitreous humour contains what cells (axons from these cells form the optic nerve)?

A

ganglion cells

42
Q

the middle layer of the retina contains several what cell types?

A

interneuron:
- bipolar = connect sensory and ganglion cells
- horizontal = connects groups of sensory cells
- amacrine = forms connections between ganglion cells

43
Q

the layers of the retina are backwards does light pass through layers of sensory cells or neurons first?

A

layers of neurons

44
Q

what is the optic disc?

A

the point where the optic nerve leaves the eye and blood vessels enter, it is located 3mm medial to and slightly above the posterior pole of the globe

45
Q

what causes a blind spot? why?

A

the optic disc, it doesn’t contain any visual receptors

46
Q

what is the macula lutea?

A

a yellowish area near the posterior pole, it marks the location of the fovea centralis

47
Q

what is the fovea centralis?

A

a thin, rod-free, cone-packed area, each cone synapses with a single bipolar cell, which in turn synapses with a single ganglion cell, no blood vessels, MAXIMUM VISUAL ACUITY

48
Q

what vessels supply the bipolar and ganglion cells?

A

retinal vessels

49
Q

what does the choroid plexus supply?

A

the rods and cones

50
Q

where would you find the retinal pigmented epithelium?

A

cell layer outer to retina and attached to choroid overlying retinal vessels

SF6: Organs of Special Senses and Endocrine Systems (13 decks)

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