Biological complexity: circadian clocks (Introduction)

by David Turell , Thursday, June 02, 2016, 14:15 (3096 days ago) @ dhw

Our bodies cycle automatically and even has correlations to personality:-https://aeon.co/essays/soon-we-will-see-chrono-attached-to-every-form-of-medicine?utm_source=Aeon+Newsletter&utm_campaign=8c7f17990b-Daily_Newsletter_2_June_20165_31_2016&utm_medium=email&utm_term=0_411a82e59d-8c7f17990b-68942561-"All life on a rotating planet is ruled by circadian rhythms. Chronobiology research has brought the importance of healthy sleep to the fore, and we have made great strides in understanding jetlag. But if we stop there, we're missing the larger point, which is that our bodies in all their complexity live and die by the clock. For decades now, scientists have understood that every bodily function is under the control of the bodyclock. In other words, physiology is four-dimensional - we might as well be different animals during the day than we are at night.-***-"The first circadian clocks originated more than 2 billion years ago, during the Great Oxidation Event. They are found in all plants and animals, and in fact are almost universal in the tree of life. (my bold)-***-"Internal clocks help living beings ready themselves for the daily events that are important to their survival: they act as a conduit between the organism and the environment. A bat's inner alarm clock wakes her at dusk in a cave with no other time cues, and she flies out in time to catch the crepuscular insects that sustain her. Many bacteria shut off their cell division mid-day, regardless of cloud cover, to protect themselves from harmful UV radiation.-***-"With so much of the talk about bodyclocks focused on sleep, it's easy to forget that all of our biological processes around the clock are organised by circadian rhythms. Every day of the internal schedule is full of appointments. Nitrogen-fixing bacteria glean oxygen from the atmosphere, and they also photosynthesise to store energy. But they can't do both at once, so they alternate between nocturnal nitrogen-fixing and daytime photosynthesis. Mammals have many such processes to orchestrate, and just about everything our body does - from metabolism and DNA repair to immune responses and cognition - is under circadian control. In humans, normal organ functioning depends on a harmony in hierarchy: synchrony among molecular rhythms within each cell, among cells in each organ, and among organs in the body. Coordinated functioning ensures that the body doesn't work against itself.-***-"The human body is teeming with clocks, arranged in a hierarchy. At the helm, a master clock in the brain's hypothalamus called the suprachiasmatic nucleus (SCN) sets the overall rhythm of the body. But each organ also has its own rhythm that's generated internally. A clock, in the broadest sense, consists of any type of regular oscillation, and these clocks take the form of a transcription-translation feedback loop that circles back to the beginning in roughly 24 hours. Clock genes activate a process that results in protein synthesis, and once the concentration of those proteins in the cell reach a critical threshold, they come into the nucleus and turn off the clock gene that produced them. Once the proteins have broken down, the gene switches on and the cycle begins again.-"Every day, the body corrects its clock to match its surroundings using daylight. A photoreceptor in the retina - the third photoreceptor after our black-and-white vision rods and colour vision cones - senses only overall light levels and reports directly to that master clock to reset it when it drifts off-course.-***-"The way your body orchestrates its cycles is different from your son's timing or your partner's. For one thing, your avian type - early bird, night owl or humming bird (in between) - is a biological reality. Early birds really do have different physiologies than night owls, because morning people have shorter circadian rhythms that drive them to sleep earlier. Women are more likely to be early birds than men, and introverts are also more likely than extroverts to be up with a smile at the crack of dawn.-"These chronotypes are largely genetic, but they also change with age. Young children and elderly people tend toward the morning, but toward late adolescence our cycles are shifted later in the day."-Comment: This is just the introduction to a long essay on timing in medical therapy, primarily cancer, where it is found that chemotherapy is best tolerated at certain times. The automaticity of cells and the whole body is what I've seen as a physician. As the article shows (see bold) the clock is two billion years old. Cells run automatically through intelligent design. They are given mechanisms they can control as responses to various stimuli.