davekm

Thanks. It is a toughie. It would be just the forearm, no hand or upper arm. Chopping my arm off would give a easy answer, but I'll pass. :D

Preferably the forearm. I can't spend big money on x-rays, nor can I chop my arm off. I've asked this elsewhere - LINK I know the volume of my forearm, using the Archimedes method, for 10 equal segments of my forearm. I've also looked at x-rays to work out roughly tissue distribution. Only issue, in terms of precision, is there is quite a big difference in density between bone, fat and muscle. On average, bone is 1.7500 g/cm and muscle is 1.0599 g/cm3.

Never mind. The answers here pretty much debunk my thoughts that sleep is dependent on the numbe of daylight hours. As mentioned, the shortest night is 0 mins in the arctic and they still sleep. http://www.thenakedscientists.com/forum/index.php?topic=50105.msg429384#msg429384

I have checked the sunset and rise for my city of residence, Sheffield, UK. There is only a 7 hour gap from sunset to sunrise in June, a 7 1/2 hour gap in July and a 8 hour 6 min gap in May. This challenges the assertion that you need 8 hrs of sleep in the summer. Our circadian rhythm evolved from homo sapiens who slept when it became dark. Furthermore, it stays light for an hour after sunset. So to follow your natural circadian pattern in the UK, you would only get 6-7 hours sleep in the summer. Likewise, there is a 16 1/2 hr period till sunrise in December, suggesting we should almost hibernate in the winter. I guess I really need to know the sunrise and sunset that we evolved to. I know homo-sapiens have the PER3 gene, I don't know if homo-erectus did though. If our biological clock was evolved from homo-sapiens that would mean we followed the sunset hours of Africa. I'm not sure what those sunset hours were, as the equator has moved as much as 110 km over the past million years. On top of that, the continents move about 20 kilometers per million years, some places move 70 kilometers per year. So I doubt I could predict past sunlight hours based on modern equatorial Africa, which is around 12 hours of sun daily. With the melatonin and light mechanism being an evolutionary thing, I wonder if we should return to waking up at sunrise and sleeping at sunset, work permitting of course. Or as close as possible. There are also links between proper circadian rhytym and longevity. This corresponds with rodent studies which shows melatonin increases longevity. Here is the sunset and sunrise in Sheffield UK in the middle of the month - Rise Set Hours of Daylight Jan 8:13 16:17 8h 04m Feb 7:26 17:14 9h 48 Mar 6:20 18:10 11h 49 Apr 6:06 20:06 14h May 5:05 20:59 15h 54m Jun 4:36 21:36 16h 59 Jul 4:56 21:26 16h 30 Aug 5:45 20:33 14h 48 Sep 6:39 19:21 12h 41m Oct 7:32 18;09 10h 36 Nov 7:31 16:09 8h 37 Dec 8:15 3:46 7h 31

Why then do people crave sweet, sugary foods? I include myself amongst those people. Is this a dopamine/endorphins reaction or just simply because it tastes nice? I know all the evidence points to it being a myth, but I just found this on wikipedia about postprandial somnolence. Is this false?

Just found this on another forum. What do you make of it Craig? "There's insulin receptors in the brain, so while you can't directly feel the sugar levels (so far as I know only the pancreas can detect those), but you can definitely feel the insulin."

duplicate post

Caffeine increases BDNF, and prevents stress induced decreases in BDNF. However, chronic BDNF downregulates the TrkB receptor. - http://www.ncbi.nlm.nih.gov/pubmed/8752592 This is true of caffeine as well. -http://www.ncbi.nlm.nih.gov/pubmed/22841916 Does downregulation of TrkB stops BDNF from performing it's functions, like neuroprotection and neurogenesis?

I think GABA chemically influences beta wave output. Beta waves are associated with logic and critical reasoning

Are there any reasons why creatine would reduce plasma trytophan and tyrosine, as indicated in this study.

Also, theanine lowers beta waves and increases alpha. Is this bad? Beta waves are associated with thinking, logic and critical reasoning Here is one of a few studies on the topic. http://www.ncbi.nlm.nih.gov/pubmed/18296328

This study indicates that GABAa lowers testosterone. Wikipedia says theanine is a GABAa agonist. http://endo.endojournals.org/content/145/2/495.abstract

Anyone?

The orienting response causes an increase in adrenaline and stress. Repeated exposure to a stimulus can cause habituation. I wonder if tv is a repeated stimulus, and thus habituation occurs. Or is every camera change a novel stimulus, so the orienting reflex is constantly triggered.

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