BioCybernetics: A Biological Clock System
Many articles on biocybernetics focus on a single system in the organism. This may be because a biological entity is thought as being too complex to be considered in its entirety.
But many system properties are only understandable when the cooperation of its parts are considered.
Cybernetics is meant to be concerned with those properties of systems that are independent of their concrete material or components. The only way to abstract a system’s physical aspects or components while still preserving its essential structure and functions is to consider relations: how do the components differ from or connect to each other? How does the one transform into the other?… Cybernetics, is interested in processes where an effect feeds back into its very cause..
An autonomous system, such as an organism, or a person, can be characterized by the fact that it pursues its own goals, resisting obstructions from the environment that would make it deviate from its preferred state of affairs.
Goal-directedness can be understood most simply as suppression of deviations from an invariant goal state. In that respect, a goal is similar to a stable equilibrium, to which the system returns after any perturbation. While the perturbations resisted in a control relation can originate either inside (e.g. functioning errors or quantum fluctuations) or outside of the system (e.g. attack by a predator or changes in the weather), functionally we can treat them as if they all come from the same, external source. To achieve its goal in spite of such perturbations, the system must have a way to block their effect on its essential variables. There are three fundamental methods to achieve such regulation: buffering, feedback and feedforward. F Heylighen 2001.
Biological Clocks and Cybernetic Systems.
Current evidence suggests that timing systems (or biological clocks), of some sort are found in every living creature.
Living organisms have developed a multitude of timing mechanisms–“biological clocks.” Their mechanisms are based on either oscillations (oscillatory clocks) or unidirectional processes (hourglass clocks).
Oscillatory clocks comprise circatidal, circalunidian, circadian, circalunar, and circannual oscillations–which keep time with environmental periodicities–as well as ultradian oscillations, ovarian cycles, and oscillations in development and in the brain, which keep time with biological timescales…. More complex timing systems combine oscillatory and hourglass mechanisms, such as the case for cell cycle, sleep initiation, or brain clocks, whereas others combine external and internal periodicities (photoperiodism, seasonal reproduction).
Biological and chemical oscillators are characterized by positive and negative feedback (or feedforward) mechanisms. L Rensing 2001.
Each body clock has been seen to have a distinct role, but harmonizes with the other sections via a precise phase relationship.
Biological systems are adapted to respond quickly to changes in their environment. Signal processing often leads to all-or-none switch-like activation of downstream pathways… Biological switches are known to be controlled by nonlinear positive feedback loops, and it is also known that multiple feedback loops make the switches even more robust.
The Circadian System
The most ubiquitous biological rhythms are those that occur with a period close to 24 h in all eukaryotes and in some prokaryotes such as cyanobacteria. A Goldbeter (2007)
The circadian clock mechanism involves transcription–translation feedback loops (TTFL) comprised of a set of core clock genes. The intracellular oscillator is composed of both positive and negative feedback/feedforward loops.
But recent evidence is demonstrating that this is not an adequate model in itself and that ‘a circadian system’ needs broader definition.
This evidence includes:
- Results suggest that non-transcriptional processes such as metabolic state may interact and work in parallel with the canonical genetic mechanisms of keeping circadian time. Redox perturbs circadian rhythms which in turn perturb redox. Lisa Wulund 2015, K Nishio 2015. N B Milev 2015. Milev and Reddy 2015, and M Putker and O’Neill 2016.
- Cryptochromes (a clock gene) role goes beyond that of a simple biological clock. A functional requirement for blue light in phase shifting circadian clocks and in altering spatial orientation and taxis in several species relative to gravity, magnetic fields, solar, lunar, and celestial radiation makes it the most interesting of the genes currently associated with both biological clocks and geotaxis… data and the literature presented here show that genes, physiology and behavioural aspects of geotaxis, biological clocks, magnetosensitivity and other types of spatial orientation, are complex, intriguing and interrelated. D L Clayton 2016.
- It has been theorises that cryptochromes are directly implicated in magnetoreception (quantum biology).
- Cryptochrome (and other clock genes) are strongly associated with time and place memory. CK Mulder 2016, A Malik 2015.
- Evidence suggests a shift away from previous notions of a single locus or neural network of food entrainable oscillators to a distributed system involving dynamic feedback among cells of the body and brain. Several recent advances, including documentation of peroxiredoxin metabolic circadian oscillation and anticipatory behavior in the absence of a central nervous system, support the possibility of conditioned signals from the periphery in determining anticipatory behavior. Individuals learn to detect changes in internal and external signals that occur as a consequence of the brain and body preparing for an impending meal. Cues temporally near and far from actual energy content can then be used to optimize responses to temporally predictable and unpredictable cues in the environment. R Silver 2011.
- Various clock genes and circadian rhythms have been implicated in growth (e.g see S A Brown 2014), including neurogenesis. A Malik 2015.
- In species varying from plants to animals, circadian rhythms influence a huge number of processes, functions, and behaviours taking place. This includes metabolic processes such as photosynthesis (circadian clock is integrated very closely with photosynthesis and its metabolic products), as well as the control of protein production, interaction and conformation, etc.
- In the case of some gut bacteria there is a bidirectional relationship between the circadian rhythms of the bacteria and those of the host. This in turn can influence the metabolism and growth. C A Thaiss et al 2016 , A C Heath-Heckman (2016)
- One central feature of all circadian rhythms is ‘temperature compensation’ which allows organisms to maintain robust rhythms with a period close to a diel cycle over a broad range of physiological temperatures.A 2010 study showed that in drosophila, who protective heat and stress response had been inhibited, the clock hardly shifts with temperature changes P B Kidd 2015. Cryptochrome dampens temperature input into the clock and therefore contributes to the integration of different Zeitgebers. C Gentile 2013
- Circadian rhythms are influenced by a number of external factors including sunlight, but also temperature, feeding – and in some species social cues. When the organism is exposed to physical clues of the time of day the circadian rhythm is gradually entrained and assumes a precise 24 hour period. If the entraining stimuli are withdrawn, the circadian oscillator reverts gradually to its free-running period. Findings support the existence of a circadian limit cycle oscillator in mammalian cells and suggest that a small number of variables determine the relaxation process after a perturbation. S Koinuma 2017
Previous articles have considered circadian rhythms as a cybernetic system e.g:
- C F Ehret wrote of ‘circadian cybernetics’ (edited by L.E. Scheving, Franz Halberg – 1981).
- T Stebbing 2011 on ‘a cybernetic view of biological growth’.
- P Cariani 2015 on ‘a cybernetic theory of brain function based on neural timing nets’.
- M Ben-Aaron 1975 wrote of the deferred-updating cybernetic theory of the mind/brain information-processing system. This theory predicts the existence of an intermediate memory, the circadian memory. This is different from, and auxiliary to, both short-term and long-term memory. One of the prime functions of circadian memory, according to the theory, is to store incoming information until it can be integrated into long-term memory.
Here it is suggested that the biological clock system should be considered as a primary cybernetic system within the living organism. No other biological system should be studied without reference to it, as it supports an overall system of self- organisation – built on the interaction of biological oscillations A Goldbeter (2007)
This article merely joins up other peoples work into an overall system. These works have been referenced so it is clear that others have provided the individual pieces of evidence that have been used to shape a specific systems approach.