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In vertebrates, the master circadian clock is contained within the suprachiasmatic nucleus (SCN), a bilateral nerve cluster of about 20,000 neurons. [10] [11] The SCN itself is located in the hypothalamus, a small region of the brain situated directly above the optic chiasm, where it receives input from specialized photosensitive ganglion cells in the retina via the retinohypothalamic tract.
Steppe eagles are diurnal, and hunt during the day. Humans are diurnal, and organize their work and business mainly in the day. [a] Diurnality is a form of plant and animal behavior characterized by activity during daytime, with a period of sleeping or other inactivity at night. The common adjective used for daytime activity is "diurnal". The ...
This is an accepted version of this page This is the latest accepted revision, reviewed on 12 January 2025. Short period of sleep during typical waking hours For other uses, see Nap (disambiguation). A man napping in a hammock, on a patio in Costa Rica A nap is a short period of sleep, typically taken during daytime hours as an adjunct to the usual nocturnal sleep period. Naps are most often ...
Looking for ways to occupy kids until bedtime? We'll help you get the party started with 30 things to do at a sleepover or slumber party.
Is it possible to have a fabulous date night for two on a $25 budget? Yes! $25 goes a surprisingly long way in creating memorable date moments during the day, afternoon and well into the...
A circadian rhythm (/ s ər ˈ k eɪ d i ə n /), or circadian cycle, is a natural oscillation that repeats roughly every 24 hours.Circadian rhythms can refer to any process that originates within an organism (i.e., endogenous) and responds to the environment (is entrained by the environment).
The activity/rest cycle (sleep) in animals is one of the circadian rhythms that normally are entrained by environmental cues. In mammals, such endogenous rhythms are generated by the suprachiasmatic nucleus (SCN) of the anterior hypothalamus. Entrainment is accomplished by altering the concentration of clock components through altered gene ...
The kiwi is a family of nocturnal birds endemic to New Zealand.. While it is difficult to say which came first, nocturnality or diurnality, a hypothesis in evolutionary biology, the nocturnal bottleneck theory, postulates that in the Mesozoic, many ancestors of modern-day mammals evolved nocturnal characteristics in order to avoid contact with the numerous diurnal predators. [3]