10 votes
Accepted

Why are fearful stimuli more powerful at night?

Short answer The increased fear responses during the night are believed to be mediated by elevated corticotropin-releasing hormone (CRH) levels in the brain that drive the fear responses in the ...
AliceD's user avatar
  • 52.4k
8 votes

A biological system to measure time

There are lots of biological clocks, or clocks made of biological components. The circadian clock is an important, though complicated, example. There are excellent engineered clocks that form some of ...
Raghu Parthasarathy's user avatar
5 votes

Why do morning people have shorter biological clocks?

Circadian rhythms are entrained by light via the suprachiasmatic nucleus, a part of the brain that receives signals from special retinal ganglion cells that are directly sensitive to (mainly blue) ...
Bryan Krause's user avatar
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4 votes
Accepted

What is blue light?

Blue light means wavelengths that appear to the human eye as blue when they are presented alone. This light is important for sleep/wake cycle regulation because this is the wavelength that cells that ...
Bryan Krause's user avatar
  • 45.7k
3 votes

How can space-time affect ageing?

According to Einstein's Special Theory of Relativity, moving objects measure shorter in their direction of motion as their velocity increases until, at the speed of light, they disappear. It also ...
AliceD's user avatar
  • 52.4k
3 votes
Accepted

Variation of length of circadian rhythm in humans in absense of time reference

This might be the study to which you refer in your answer, the people tested averaged a daily cycle of 24 hours and 11 minutes with a surprisingly small variation in their rhythms: The variation ...
Koen vd H's user avatar
  • 837
2 votes

Does apoptosis occur more at a particular time of day?

Your question is quite well-formed, however all I can say so far is: I don't know. Maybe it is known, however I could not find any information on this in the literature. In general, little is known ...
Aquifex's user avatar
  • 21
2 votes

Does sleep duration vary for animals based on time of the year?

Yes, people, as well as animals regulate their drowsiness by light. There's a well known experiment conducted by Michel Suffre on himself in 1972. When he spent a month with no light and no ...
Probably's user avatar
  • 2,438
1 vote

How do people wake up just before their alarm goes off?

The biological answer is presumably cryptochromes. The foregoing applies to humans who have CRY2 blue light receptors in the inner retina (the neural layer, not the photoreceptors). I've seen claims ...
Mike Serfas's user avatar
  • 2,465
1 vote

Sleep deprivation relation to growth rate and mental health in adolescence

A couple of papers (from the same group, it seems) defines sleep deprivation in adolescents as less than 6hr of sleep within a month. They found that sleep deprivation increases health risks, ...
TumbiSapichu's user avatar
1 vote
Accepted

Circadian clocks in enzymes

Molecular feedback mechanisms create rhythmic patterns. The circadian rhythm is driven by a handful of genes, which in turn can regulate a number of downstream factors. Here is a very nice ...
Frieke's user avatar
  • 1,127
1 vote

How would our circadian rhythm change over time if we had no sunlight whatsoever?

Say we can live for 10,000 years, how would our circadian rhythm be different 10,000 years from now after zero exposure to sunlight? Probably almost the same. A circadian rhythm has - by definition -...
Nicolai's user avatar
  • 4,391
1 vote

Is there a difference between sleeping late and waking up late vs sleeping early and waking up early?

There is a popular theory that each person has a certain "chronotype" [Ref 1]. Based on your genetics, you could be naturally an early person ("Lark") or a late person ("Owl") [Ref. 2]. What will ...
Louis Leung's user avatar
1 vote
Accepted

How does the body count time in the short term?

Detection of rhythm is a separate function from general musicality, but both can be affected by the same brain damage, or they can be independently affected: A range of rhythmic deficits has been ...
iayork's user avatar
  • 14.2k
1 vote

Why aren't circadian rhythms exactly 24 hours long?

Biological/organic systems are notorious for imprecision, making a perfect 24-hour cycle practically impossible - nevermind the fact that "hours" are a purely artificial concept that humans invented ...
user1258361's user avatar
1 vote

Would constant light or fading light be registered as more wakefulness promoting by the Supra Chiasmatic Nucleus?

There is no light adaptation (such as Arrestin-mediated light adaptation http://www.sciencedirect.com/science/article/pii/S0896627303003908) or other negative feedback loop that attenuates melanopsin ...
Jory's user avatar
  • 470

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