Sleep-wake cycle
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The Sleep-wake cycle is a diurnal rhythm the human body oscillates in between conscious and unconscious states, the mechanics of which span several fields of science including psychophysiology, endopharmacology, metabolomics, and psychology. In this cycle a person will optimally spend 7 hours in the sleep state[1] which is similar on the surface to unconsciousness (although the phenomenon of lucid dreaming is contradictory to the term unconsciousness). The sleep state is often preformed at night as this is the evolutionary norm for humans, as evidenced by the fact that the hormone melatonin is released during darkness and contributes to the desire to sleep.[2] Although melatonin in this instance serves as a regulatory mechanism for making sure humans sleep once a day during night, it is not the causative factor as humans are able to sleep even during daylight if they are sleepy enough. Though it should be noted that this can lead to circadian rhythm sleep disorders.
Biology
The biological process outlined here is cyclic and although it is outlined in a linear form it is better understood in a way that the end leads to the beginning to start over again.
After waking
- Lack of Adenosine activating the (A(2A)R) receptor is significant enough to decrease GABA release in the tuberomammillary nucleus enabling histamine to wake one up and cause vigilance.[3]
- Exposure to blue light frequencies mainly between 460 and 480nm trigger melanopsin cells in the eyes to send a signal to the suprachiasmatic nucleus (SCN) which sends GABA to the pineal gland, inhibiting it from releasing melatonin thereby causing levels to decline.
- Ghrelin has built up since the food eaten before sleep has been digested and the stomach is empty, this induces hunger thereby causing one to eat.[4]
- ATP from the food is metabolized into adenosine which begins to accumulate around the adenosine receptors.[5]
Approaching night
- High levels of adenosine activating the adenosine receptor A1 inhibit cholinergic neurons in the basal forebrain[6] thus gradually causing cognitive decline.[7]
- Activation of adenosine receptor (A(2A)R) causes the release of GABA in the tuberomammillary nucleus to inhibit histamine, thus inducing sleepiness.[8]
- In the presence of insulin melatonin causes upregulation of leptin allowing one to fast while they sleep[9] (If one has been fasting before sleep insulin levels will be low causing melatonin to downregulate leptin instead of upregulating it, thus encouraging one to eat before they sleep)
Fast asleep
See also
References
- ↑ http://archpsyc.jamanetwork.com/article.aspx?articleid=206050 | Mortality Associated With Sleep Duration and Insomnia
- ↑ http://www.ncbi.nlm.nih.gov/pubmed/7768078 | Sleep-inducing effects of low doses of melatonin ingested in the evening.
- ↑ http://www.ncbi.nlm.nih.gov/pubmed/15748171 | An adenosine A receptor agonist induces sleep by increasing GABA release in the tuberomammillary nucleus to inhibit histaminergic systems in rats.
- ↑ http://www.ncbi.nlm.nih.gov/gene/51738 | ghrelin and obestatin prepropeptide [ Homo sapiens (human) ]
- ↑ http://thebrain.mcgill.ca/flash/a/a_11/a_11_m/a_11_m_cyc/a_11_m_cyc.html | MOLECULES THAT BUILD UP AND MAKE YOU SLEEP
- ↑ http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3362278/ | Adenosine inhibits glutamatergic input to basal forebrain cholinergic neurons
- ↑ http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2659740/ | The Role of Acetylcholine in Learning and Memory
- ↑ http://www.ncbi.nlm.nih.gov/pubmed/15748171 | An adenosine A receptor agonist induces sleep by increasing GABA release in the tuberomammillary nucleus to inhibit histaminergic systems in rats.
- ↑ https://www.ncbi.nlm.nih.gov/pubmed/15572654 | Melatonin enhances leptin expression by rat adipocytes in the presence of insulin.