Sleep Disorders
Divya Vohora in The Third Histamine Receptor, 2008
Thus, the sleep/wake cycle is predominantly regulated by the integration of two mechanisms: Process S (homeostatic) and Process C (circadian). The circadian component influences sleep by integrating it to the time of day and behaves like an endogenous clock that can run in the presence or absence of external cues. The homeostatic component is related to the duration of wake [19,28]. Therefore, the longer an individual is awake, the higher the sleep drive. The accumulation or dissipation of sleep pressure resides in the interaction between the two components. For a diurnal species, Process S accrues during the day and diminishes during the rest period. The circadian Process C for sleep propensity, however, obtains its peak during the latter portion of the night. Thus, the diurnal animal will experience the onset of sleep when the greatest separation between Processes S and C occurs.
Contrast adaptation
Pablo Artal in Handbook of Visual Optics, 2017
Because the light sensitivity of humans rods is similar to the one of nocturnal mammals (also our rods can respond to a single photon), the only way for nocturnal animals to increase their CS at night is to increase retinal illuminance. This is achieved by lowering the aperture stop, that is, the ratio of focal length to pupil size (Figure 21.6). For instance, a barn owl has an aperture stop of less than 1, and a diurnal animal like a chameleon has an aperture stop of about 5. The ratio of retinal illuminance in both types of eyes is determined by the ratio of the squares of the two aperture stops, 1/25. Accordingly, the retinal image is 25 times brighter in the owl compared to the chameleon. Young children may have an aperture stop of around 2 (anterior focal length 16.7 mm, pupil size 8 mm), which means that their retinal image is only about four times darker than in an owl. Since CS rises with the square root of luminance in dim light, retinal illuminance can explain a difference in CS of a factor of 2. However, it was found that nocturnal mammals, like cat and owl, have about a six times higher CS at low light levels (Pasternak and Merigan 1981; Orlowski et al. 2012) than human subjects, and the difference cannot be fully explained only by optics. Cats and dogs have developed highly reflective layers behind the photoreceptors, the tapetum lucidum, to increase the chance that photons can be absorbed in a second pass. It has been calculated that the tapetum increases light sensitivity (and thereby CS) by further 29%. Because reflected photons are more scattered, this may be at the cost of visual acuity.
Freeruns
Sue Binkley in Biological Clocks, 2020
In contrast, when a diurnal animal, such as the house sparrow, is placed in constant light (LL), its activity lasts longer (e.g. activity time, alpha = 17 hours) and its rest period is reduced in comparison to house sparrows in DD (e.g. activity time, alpha = 8 hours). Thus a nine-hour difference in activity time can be produced by light!
Wheel-running activity rhythms and masking responses in the diurnal palm squirrel, Funambulus pennantii
Published in Chronobiology International, 2020
Dhanananajay Kumar, Sanjeev Kumar Soni, Noga Kronfeld-Schor, Muniyandi Singaravel
Moreover, several experiments on diurnal rodents, like O. degu (Kas and Edgar 1999; Vivanco et al. 2010a, 2010b) and A. niloticus (Blanchong et al. 1999) have described a change in activity pattern in the presence of a running wheel. In the above studies, most individuals were primarily diurnal, but access to a running wheel caused some of them to change their activity pattern to nocturnal. When the wheels were removed, the diurnal activity pattern reappeared in the same individuals. In contrast, golden spiny mice A. russatus, which are diurnal in the field but are more nocturnal in the laboratory, increased their nocturnality in the presence of a running wheel (Cohen et al. 2009). The above studies indicate that diurnality is a highly variable and more complex characteristic compared to nocturnality. Therefore, it is essential to explore and study the circadian system of different diurnal species to enable understanding of the key mechanisms responsible for diurnality and nocturnality.
Temporal flexibility in activity rhythms of a diurnal rodent, the ice rat (Otomys sloggetti)
Published in Chronobiology International, 2020
In any functional ecosystem, many different species co-exist, each with its own unique niche (Kronfeld-Schor and Dayan 2008). The niche of a species is shaped by interactions with biotic and abiotic variables in its environment and is defined both in terms of space and time. Time is a critically important element of an ecological niche, and animals arrange their temporal activity to optimize their survival and reproductive potential (Campi and Krubitzer 2010). Although the temporal niches of mammals are frequently categorized as diurnal or nocturnal, there exists a gradient of diurnality and nocturnality, both between and within species where strictly nocturnal and diurnal are the opposite ends of the spectrum (Refinetti 2008).
Spatiotemporal variability in activity patterns of urban street cattle as function of environmental factors
Published in Chronobiology International, 2019
Bhupendra Kumar Sahu, Arti Parganiha, Atanu Kumar Pati
Cattle are diurnal in nature (Braghieri et al. 2011; Dolev et al. 2014) and our results on foraging behavior confirm their diurnality. It is evident from the Cosinor analyses of the pooled data that the foraging time was mostly restricted to the late morning hours with the peak located at 11.54 h. Compared with the findings of Arya et al. (2019), the peak foraging time was found to be delayed by two hours in the present study. This difference could be ascribed to the difference in the geographical locations of the studies. Nonetheless, the foraging activity is mostly restricted to the morning hours (Arya et al. 2019; Braghieri et al. 2011).
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