who did not sleep for 14 years in ramayana
Urmila As the night fell on the first day of the exile, Lakshmana stood guard over Ram and Sita with a strong resolve not to sleep until the exile ended. As Lakshmana stood guard over his brother's dwelling, a resplendent goddess called Nidra Devi manifested before Lakshmana. On Lakshmana's enquiry, she introduced herself as the Goddess of Sleep and informed him that not sleeping for fourteen years is an act of defiance against nature. Lakshmana requested Nidra Devi for a way out so that he could carry out his Dharma towards his brother. Impressed by Lakshmana's devotion towards his brother, Nidra Devi put forth a workaround that if someone bears the burden of Lakshmana's share of sleep for fourteen years, he could have the exemption for fourteen years. Lakshmana requested Nidra Devi to approach his wife, Urmila, to help him.
Neuroscience of sleep In 1993, a different model called the opponent process model[92] was proposed. This model explained that these two processes opposed each other to produce sleep, as against Borbely's model. According to this model, the SCN, which is involved in the circadian rhythm, enhances wakefulness and opposes the homeostatic rhythm. In opposition is the homeostatic rhythm, regulated via a complex multisynaptic pathway in the hypothalamus that acts like a switch and shuts off the arousal system. Both effects together produce a see-saw like effect of sleep and wakefulness.[74] More recently, it has been proposed that both models have some validity to them, while new theories hold that inhibition of NREM sleep by REM could also play a role.[93] In any case, the two process mechanism adds flexibility to the simple circadian rhythm and could have evolved as an adaptive measure.