Brainscape's Knowledge GenomeTM

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


See full index

Biology 465 > Environmental Light, Circadian Rhythm and Breast Cancer > Flashcards

Environmental Light, Circadian Rhythm and Breast Cancer Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

What has occurred to humans now that artificial lighting has been introduced?

A

Humans have spent extended periods of time exposed to artificial light (a new spectral composition), while spending less time being exposed to natural sunlight and darkness we evolved with.

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

Why is artificial light a problem?

A
  • blue 480nm is needed to make serotonin but inhibits melatonin production
  • 295nm UVB is needed to make Vitamin D
  • artificial light is lacking this wavelength of the broad spectrum noon sun
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Why does the wavelength 480nm have to be absent to produce melatonin?

A
  • at this wavelength, seratonin is produced

- it has to be absent because light inhibits the production of melatonin

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

What are circadian rhythms?

A
  • physical, mental and behavioral changes that follow a roughly 24-hour cycle
  • responds primarily to light and darkness in an organism’s environment
  • usually endogenously generated and self-sustaining
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Where are circadian rhythms found?

A

In most living things, such as animals, plants and many tiny microbes

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

What are the two ways light acts on the body?

A
  • the primary optic tract governs sight and and responses

- the retinohypothalamic tract is most sensitive to blue light stimulation energy in the wavelength of roughly 459-485nm

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

What is the primary optic tract responsible for?

A
  • visual effects

- visual reflexes

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

What is the Retinohypothalamic tract responsible for?

A

Acute and longer-term biological/behavioral effects

  • acute effects include melatonin secretion
  • longer-term effects include circadian regulation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What does light signal through?

A

The melanopsin protein
- it undergoes a chemical change when exposed to light received by intrinsically photosensitive retinal ganglion cells in the back of the eye

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

What are some health effects of the deregulation of the circadian clock?

A
  1. insomnia and sleep disorders
  2. reduced alertness
  3. poor cognitive and motor function
  4. depression, bipolar disorder and seasonal affective disorder
  5. cardio-vascular disease
  6. altered hormone levels
  7. obesity
  8. early-onset diabetes
  9. altered immune function
  10. cancer - breast, prostate and colon
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What does the retinohypothalamic tract govern?

A

The circadian, endocrine and neurobehavioural functions

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

What hormones relate to breast cancer and the hypothalamus exposure to light?

A
  • GnRH
  • Estrogen
  • Progesterone
  • Melatonin
  • Serotonin
  • Vitamin D (Calcitriol)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is melatonin?

A
  • the darkness hormone
  • secreted only at night (need absence of 480nm light)
  • its precursor is serotonin
  • secreted into the blood by the pineal gland to initiate sleep
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Why do melatonin levels vary in a daily cycle?

A

It allows the maintenance of the circadian rhythms of many biological functions

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

How does the suprachiasmatic nucleaus (SCN) work?

A

It works like a clock.

  • exposure to first light: the clock in SCN begins performing functions like raising body temperature and releasing stimulating hormones like cortisol
  • delays release of hormones such as melatonin until later when darkness arives
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is serotonin?

A

It’s a neurotransmitter that can also function as a hormone

  • highest levels in the afternoon (need 480nm light)
  • derived from tryptophan (constituent of most protein-based foods)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Where is serotonin produced?

A
  • most is produced in the gut, but the remainder is produced in the central nervous system where it functions to regulate mood, appetite, memory and sleep
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is Vitamin D essential for?

A

The formation of normal bones and teeth by maintaining blood levels of calcium and phosphorus but also cell differentiation and development

19
Q

What are some other names for Vitamin D?

A
  • Any of the fat soluble vitamins: D1, D2, D3

- calcitriol = active vitamin D

20
Q

Why is Vitamin not considered a true vitamin but a hormone?

A

We make most of it (~90%) from a metabolite of cholesterol that is present in the skin when exposed to UV light

  • then further processed in the liver and kidneys
  • also can be obtained in our diet (milk products and fatty fish)
21
Q

Where are vitamin D receptors found?

A
  • bone
  • kidney
  • gut
  • immune cells
  • testis
  • breast
22
Q

Why is vitamin D important in cancer?

A

It signals for antiproliferation

23
Q

How is breast cancer and the hormones associated?

A

Breast cancer has been found to be associated with low levels of melatonin, serotonin and vitamin D

24
Q

What environmental changes have been associated with the increased risk of chronic diseases like cancer?

A
  • disruption of biological rhythms (daily, monthly, seasonally) alters hormones
  • the new “built indoor environment”/artificial light which alters the exposure to natural sunlight and darkness
  • geological location and population differences also affect the exposure to light (different latitudes and living in cities/rural areas)
25
Q

What is the exposure to LAN associated with?

A
  • Light at Night (LAN)

- it is correlated with breast and prostate cancer

26
Q

Why is the shift to darkness such a key factor?

A
  • It’s a key factor in the production of melatonin and sleep regulation
  • exposure to light at night diminishes melatonin production
  • since light stimulates serotonin production, altered levels may lead to low levels of melatonin
27
Q

What is the relationship between breast cancer, light and circadian rhythm?

A
  • changes in exposure to light affects biological rhythms, which alters teh metabolism of key hormones (includes GnRH, estrogen, progesterone, testosterone, vitamin D and melatonin)
  • alters neurotransmitters including dopamine and serotonin
  • alters micronutrients including iron
    These changes all increase the risk for chronic disease including breast cancer
28
Q

Summarize the problem with decreased natural daytime light and increased artificial light exposure.

A

Decreased natural daytime light exposure and increased artificial light exposure at night leads to an increased risk of breast cancer

29
Q

What is the rate limiting step in the melatonin biosynthesis in the pineal gland?

A

5HT, serotonin to N-acetylserotonin (NAS)

- the process starts with tryptophan and ends with melatonin (N-acetyl-5-hydroxytryptamine)

30
Q

Are Vitamin D levels also circadian?

A

Yes, like serotonin and body temperature, the serum concentration of vitamin D peaks after mid-day

31
Q

What is the role of Vitamin D?

A
  • regulates calcium absorption

- has important effects on cell longevity and immune functions

32
Q

What are the three essential elements in our biological clocks?

A
  1. A central oscillator that keeps time in the SCN
  2. The ability to sense time cues from the environment and to reset the clock as the seasons change; and varying light cues
  3. A series of outputs tied to distinct phases of the oscillator that regulate activity and physiology
33
Q

Define the period of in Circadian clocks

A

The time to complete one cycle (top of one peak to the next peak)

34
Q

Define the amplitude of rhythm in Circadian clocks

A

One half of the peak-to-trough distance (one wave is 2 amplitudes)

35
Q

What is a phase defined in?

A

Zeitgeber time (ZT)

36
Q

What is Zeitgeber time?

A

Zeitgebers are cues and can be any stimulus that imparts time information to the clock
- have the ability to entrain the clock

37
Q

Where does the central clock reside in mammals?

A

In the suprachiasmatic nucleus (SCN), which is a small region in the hypothalamus of the brain that contains ca. 20000 neurons

38
Q

What are the roles of the SCN?

A
  • produces a rhythmic output that consists of a multitude of neural and hormonal signals that influence sleep and activity
  • signals set the peripheral clocks present in the body
39
Q

How is the SCN clock reset? And what is it sensed by?

A
  • by external light of specific wavelengths

- this is sensed by the ganglion cells of the retinal and carried by the RHT

40
Q

When is the major anabolic period for estrogen?

A

Between 6-9am

41
Q

What does the central clock of the SCN control?

A
  • rest/activity rhythms

- entrained on a daily basis by the dark/light circle

42
Q

When does estrogen and testosterone peak?

A

During the rest period in humans

43
Q

What is the reverse transcript of erythroblastosis gene-alpha (Rec-erb-alpha)?

A

A nuclear receptor oncogene

- first discovered in the 1980s

44
Q

What is the ligand for Rev-erb-alpha? What does the receptor-ligand combination do?

A
  • heme
  • this receptor ligand combination inhibits and fine tunes the clock, allowing the anabolic processes controlled by estrogen and testosterone to move forward

Biology 465 (15 decks)

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