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Flashcards in Photobiology Deck (54)
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1

What is the wavelength of UVR?

100-400nm; 5% of solar radiation

2

Wavelengths less than what wavelength do not penetrate the earth's atmosphere and what are these called?

290nm do not penetrate because of the ozone, called UVC and it can be lethal if it does

3

What light is between 290-320nm? What filters them out? What is this spectrum referred to as?

UVB; window glass filters out; sunburn spectrum; SPF testing based on this

4

What spectrum is UVA? Does it penetrate glass? How deep does it penetrate? What is it responsible for?

320-400nm; least potent and does penetrate glass but it does penetrate deeper than UVB so it is responsible for photo aging.

5

List some modifications in UVR on Earth.

Elevation, atmosphere, latitude, reflection, clouds, solar flare, season, time of day

6

How much does the ozone block?

Almost all <300nm

7

What is the percentage of light that is UVA that reaches the earth's surface?

95-98% which means the remaining percent is UVB and UVC blocked completely

8

How much % increase is seen in UVR with each 1000 feet increase in altitude?

4%

9

How much do most surfaces reflect?

<5% UVR

10

How much does water reflect?

7%

11

How much does sand reflect?

25%

12

How much does fresh snow reflect?

80%

13

What does cloud cover do to UVR?

Scatters but doesnt absorb

14

What happens when sunlight hits the skin?

Some reflected, some absorbed in epidermis and dermis by DNA, some penetrates deeper

15

What is the reaction to a given wavelength called?

Action spectrum

16

How is action spectrum determined?

Properties of molecule that initiates the response: chromophore

17

*****What is the major UVB chromophore in the skin?*****

DNA (urocanic acid, armoatic amino acid)

18

What is responsible for the majority of the effects of UVR on skin?

UVB

19

What do acute and chronic responses to UVR depend on?

Skin type

20

What do skin types I-VI vary in?

Susceptibility to burning, ability to tan, and risk of skin cancer (pretty much goes from ginger/albino to black/brown skin)

21

What are some of the acute effects of UVR on skin?

Inflammation(sunburn), immunomodulation, tanning, epidermal hyperplasia, Vitamin D synthesis, DNA damage (apoptosis or repair)

22

What is sunburn mostly due to?

UVB

23

What is erythema from sunburn the result of?

Vasodilation

24

What is heat of a sunburn the result of?

Increased blood flow

25

What is swelling of sunburn due to?

Vasopermeability

26

What is pain/pruritis of a sunburn due to?

Release of cytokines

27

When does hyperkeratosis and acanthosis happen in a cell that has been sunburned?

72 hours after sunburn

28

What are the two types of suntans?

Immediate and delayed

29

What is the immediate tan response caused by?

UVA and visible light, fades within an hour, due to oxidation and redistribution of existing melanin

30

What is the delayed response tan caused by?

UVB and it is gradual (visible in 72 hours and lasts for weeks); caused by increased melanin synthesis and increased transfer of melanosomes to keratinocytes and can provide some photoprotection