Enterocytes and neurones both have capability to learn, that means they can connect each other with their environment. So they can detect environmental changes, then analyze and after may react accordingly. Secretion of enzymes on the part of enterocyte, depending on feed changes, and adaptation to awake/sleep rates on the part of neuron, both are basic examples of that capability to learn. Lots of reactions to environmental changes can be found out in nature but, when those changes are repetitive an also repetitive response is produced, and it’s called conditioned reflex.

Although enterocytes and neurons are actually apart from the outside, their previous cells were directly connected to environment. In fact, enterocytes are epithelial cells and neurons are cells coming from annelid ganglions which sensitized to external luminous stimulus thanks to rodopsin storage.

Once those cells are able to learn and react to environment changes we deduce that cyclic changes induce to cyclic response and so cyclic rates appear in unicellular and pluricellular organisms.

In earliest research in these cycles, we emphasize those from Jean Jacques Dortus de Mairan about Helianthus annuus (sunflower) in the XVII century. This plant reacts to blue fraction of sunlight and turns dayly as a result of sun’s position. In the XIX century, Agustin Pyrame de Candolle proved that the period of plants movements cycles is a solar day long under constant conditions. And in the XX century Jurgen Aschoff (author of Aschoff rules), Rutger Wever and Michel Siffre they all studied temperature diary rates in humans and relation with sleep.

All previous researches helped Franz Halberg to define a new science called chronobiology, first based on studying diary cycles or circadian.

However, it’s proved that not all cycles have one solar day length, and that’s why Yves Ruckebush classified in 1991 animal rates in:

-Infradian cycles: rates with more than 28 hour frequency (related to reproduction, depending on adaptation to lunar phases, circalunar or to translation earth movement, circanual).

-Circadian cycles: one solar day frequency, specially related to awake/sleep and influenced by serotonin and melatonin.

-Ultradian cycles: less than 20 hour frequency, related to feeding and linked tp neuropeptide NPY.

The first circadian rates appeared in most primitive cells (Archeas) by selection and so when replication took place in darkness time descendants may not be concerned to ultraviolet rays. So histones (proteins linked to DNA replication) got linked to those rates appearance and their concentration in different kind of cells may be a related element to these circadian cycles. Neurospora fungus maintains this circadian way to replicate its genetic supplies and circadian cycle of Synechococcus elongates Photobacteria may be regulated.

The appearance of multicellular organisms and so specialized cells may have modified their cycles according to internal environments less concerned by basic rates of light or darkness, but essentially with a basic design.

Nowadays genes are known that regulate rates in Drosophila (Seymur Benzer 1979), photosynthesis, nitrogen use, the opening of petals in plants (AndreW Millar 2011) and ones in mammals located in the supraquiasmathic nucleus of medium hypothalamus.

It is known as well that most of non-nervous cells maintain their circadian rates like the liver ones, reply to feed cycles better than luminous, the esophagus, lungs, timus, spleen, blood cells, skin cells and suprarenal gland. Also olfactory bulb and prostate may suffer rhythmic oscillations in “in vivo” cultures, which suggests that they may have peripheral oscillators or their own clocks synchronized with light mainly neurons and with fees enterocytes.

So we can conclude that both enterocyte and neuron, with capability to learn, react to environment by creating their own cycles and they are the engines to move the cycles of other cells biochemically connected to them. Once neuron and enterocyte cycles exist, we may consider phylogenetic influence in parts of these cycles so that one infradian, circadian or ultradian cycle would be divided in subcycles from LUCA to every actual specie and their specialized cells.

This brings best chances in researches in new drugs and mainly in application of pronutrients and nutrogenics to improve health and productive efficiency as it’s shown in the following example according to calcium metabolism in layers. They can settle 600 gr of calcium in eggshell during 52 weeks (30 times calcium in the body of the bird).

So birds must recover the whole calcium of their organisms each period of 2 weeks. That means high levels of enterocytes absorption. But not all day long, cause enterocyte cycles prove that 60% of the absorption is made during 25% of time (4 hours between 8 and previous hours to next egg-laying).