Physiological Oscillators

An oscillation is defined as any periodic vibration relative to an equilibrium position, which is characterized by: (1) Frequency (the number of complete oscillations occurring in a given unit of time); (2) Period (the time required for a complete oscillation or vibration); and (3) Amplitude (the maximum displacement of a wave crest from its equilibrium position)

Some cellular biochemistry demonstrates intrinsic rhythmic (oscillation) activity that creates a need to coordinate with the extracellular environment. Oscillation allows communication between cells because waves can influence each other through the processes of entrainment, modulation, and phase coherence

Many biological phenomena within the body show "Rhythmic pattern". In rhythms, energy is provided regularly, but is delivered as a series of sharply focused impulses rather than as a smooth sinusoidal change. Therefore, these physiological phenomena occur physiologically as sharp neuronal pulses fluctuating in different times within a day, month, or year. When the physiological rhythm fluctuates within a period of 24 hour, the rhythm is called "Circadian rhythm", referenced to the rotation of the Earth. The word “Circadies” comes from Latin: circa = about, dies = day. In humans, there are two main circadian peaks for sleep per day: in early morning (3-5 AM), and in the early afternoon (2-3 PM)  

Most cells in the body have their own oscillators, which regulate their functions through time. The rule is this, most of the biological activates in the body shows variability as time passes; therefore, the cells have to "Synchronize" their activities with time to keep the internal homeostasis in harmony with the external environment

Entrainment is defined as the process by which an external process (light-dark cycle) synchronizes the internal pacemaker of an organism. In humans, entrainment happen every day when a stimulus (e.g., light exposure) resets the internal pacemaker to compensate for the difference between the intrinsic period of the pacemaker and the environmental cycle

The neuronal oscillators can be considered as "Clocks". These clocks have to be synchronized to express their activities according to time. The neuronal synchronization has a genetic component and external environmental component (Entrainment). The external environmental component cues that can synchronize (entrain) the neuronal oscillators are known as (Zeitgebers meaning ‘time givers’ in German, a concept coined by Jürgen Achoff). In humans, the zeitgebers include many things like: light, music, and even Tai Chi Chuan practice

Examples of physiological, rhythmic oscillation phenomenon include:

1. The menstrual monthly (Circatrigentan) cycle: is modulated by, body temperature variability. In normally cycling females, the body temperature varies in a predictable manner within the menstrual cycle (increased in the luteal phase)

2. Sleep/wakeful cycle: is mediated by the hypothalamic suprachiasmatic nucleus in respond to the light-dark cycle

3. Diurnal hormonal secretion: for example, cortisol is produced by a subset of adrenocortical steroidogenic cells that work as oscillators (Hypothalamus-pituitary-adrenal axis)


 Selected references

1. Rothwell JC. Physiology and Anatomy of Possible Oscillators in the Central Nervous System. Mov Disord; 1998 13: 24–28

2. Agarwal S et al. Efficient multiscale simulation of circadian rhythms using automated phase macromodelling techniques. Pac Symp Biocomput 2008:402-13