Definition of circadian rhythms

Chronobiology is a branch of biology which studies circadian rhythms, that is to say the biological rhythms which fluctuate over a cycle of 24 hours.

The two types of circadian rhythms:

  • Physiological rhythms: wake-sleep pattern, body temperature, etc.
  • Biological rhythms: melatonin, cortisol, growth hormones.

These different rhythms are all synchronized together and are controlled by our biological clock, located in the superchiasmatic nucleus, themselves housed in the hypothalamus within our brain.

 

The biological clock is based on three synchronizers :

1. Melatonin, also called the “sleep hormone”, which is secreted by the pituitary gland (which gives information about the alternation of day/night) and “resets” the body with its environment.

2. Light (alternation night/day) if it is received by the eye receptors in a sufficient quantity and if it is made up of good wave lengths (blue light)

3. Lastly, social factors (family life, leisure, sports, etc.) also serve as synchronizers.

The main circadian rhythm is the alternation of wake/sleep but other rhythms exist which vary from day to day : body temperature, our cortisol level, melatonin secretion, etc...

The body also searches for a temporal balance between itself and the outside world. When our internal clock is no longer synchronized with the actual time, a pathological situation follows, of which the principal symptoms are trouble sleeping, waking up and temperament.

Discover how circadian rhythms work

with Roland Pec - Sleep specialist and chrono-therapist