Biological rhythms: definition, types and operation

Biological rhythms: definition

Surely we have all heard at some point in our lives that people are animals of habit. This expression, besides being true, hides an infinite number of processes that our body carries out to keep those habits at bay.

These processes refer to the biological rhythms , which determine practically all the main activities of our organism, from the need for sleep, the sensation of hunger or the rhythm with which we blink.

Related article: “The 9 stages of human life”

What are biological rhythms?

Biological rhythms are understood as the oscillations that occur in physiological levels and variables within a time interval. These oscillations depend on an internal chronometer or clock and external or environmental variables that intervene in their synchronization.

Both human and animal habits and activities always have a regular rhythm and harmony. In a manner of speaking, living implies a rhythmic phenomenon that marks us when we eat, when we drink, when we sleep, etc.

In this way, if we stop to think about the relationship between a habit or bodily habit and its relationship with time , we can observe that all of them occur in a cyclical order or cadence which makes us think that there is something in our organism, or outside it, that is in charge of regulating them.

The external agents that regulate our daily habits are much more common than is sometimes thought. The environment, seasonal changes, hours of light or cosmic changes such as the phases of the moon play a very important role in regulating the activities of our organism.

The main internal structures involved in this regularization are the nervous system and the endocrine system, which are influenced by these external agents. However, there are a number of internally controlled rhythms such as the heart rate or breathing times. These other rhythms should be classified in a separate group due to their endogenous character.

Types of biological rhythms and functionality

As mentioned above, chronobiology distinguishes up to three types of biological rhythms according to their duration. These rhythms are called: circadian, infradian and ultradian .

1. Circadian rhythms

Taking into account the etymological origin of this term: circa-around and dies-day; we can correctly assume that circadian rhythms are those needs or body habits that occur every 24 hours approximately.

The best known and most illustrative example is the sleep cycle. Usually the need for sleep always appears at the same time and any alteration of this rhythm sometimes involves some kind of disorder or sleep disorder.

If we consider this example, it is not unusual to think that these habits depend largely on external regulating agents such as daylight. Hence, it is always recommended to sleep in complete darkness because even artificial light can disrupt our sleep cycles.

Such is the influence of these exogenous regulators that they can even influence the course of some diseases or psychological conditions. In the case of depression disorder, it is common for people to report a worsening of psychological symptoms during the first hours of the day, which then moderate throughout the day.

2. Infradian rhythms

By infradian rhythms we mean all those habits and activities of the organism that occur with a cadence of less than 24 hours, that is, less than once a day . Although this may seem strange, there are certain body habits that work with these oscillations.

The most common example is the menstrual cycle, since it is completed once every 28 days. Other phenomena that occur with a similar cadence to that of the menstrual cycle are the lunar cycles and tides, which is why on many occasions attempts have been made to establish an influence of the lunar phases on the different stages of women’s cycles.

However, this relationship has never been scientifically proven. Those who defend it justify this impossibility on the grounds that there are a multitude of day-to-day factors that interfere with the coordination of both rhythms.

3. Ultradian rhythms

Although less known and less subject to external influences, there is a series of rhythmic movements that occur with a frequency of more than one every twenty-four hours.

These rhythms are the heartbeat, blink, breathing rhythm, or REM sleep cycles that occur every 90 minutes.

How to maintain biological rhythms

As commented above, since these biological rhythms are conditioned by numerous external and environmental factors they can easily be altered as a result of any change, either in the environment or due to a modification in our daily routine.

To avoid the possible consequences of these variations in our biological rhythms (insomnia, change of moods, changes in appetite, etc.) it is advisable to maintain a daily routine that allows us to maintain our energy.

Below are a number of recommendations to keep our biological rhythms intact.

1. Getting up and going to bed at the same time

As far as possible, it is advisable to always start and end our day at the same time, or at least at approximate times. The moment we wake up marks the beginning of the activation phase of our bodies.

However, it is also necessary to get a few hours of sleep. That is, if we go to bed later than usual for whatever reason, it is better to get the recommended 7 or 8 hours of sleep rather than get up too early just to keep to the schedule.

2. Maintain routine even on vacation

Even though it may seem unappetizing, it is advisable to keep our usual schedules even during the holidays . This way we will keep our biological rhythms practically intact and it will be much easier for us to conserve energy once they are over and we have to return to the routine.

If necessary, a relatively structured schedule can be kept in advance, so that the increase in free time does not cause us to postpone tasks whose regularity needs to be enhanced.

3. Always eat at the same time

Like sleep, the sensation of hunger is also subject to a temporary cadence . In addition, all biological functions depend on how and when we nourish ourselves, so failures in feeding and regularity of eating can create a chain effect. Therefore, it is essential to maintain stable schedules for the main meals. This will help control the feeling of hunger and prevent binge eating.

4. Keeping a diary or journal with our habits

If we monitor our daily activities or habits, it will be easier for us to fulfil all those obligations or objectives that we set ourselves on a daily basis. Therefore, avoiding mismatches and irregularities in the organization of our week will favor the establishment of healthy and consistent biological cycles.

Bibliographic references:

  • Aschoff, J. (ed.) (1965). Circadian Clocks. Amsterdam: North Holland Press.
  • Richter, H.G., Torres-Farfán, C., Rojas-García, P.P., Campino, C., Torrealba, F., Serón-Ferré, M. (2004) The circadian timing system: making sense of day/night gene expression. Biol Res.;37(1):11-28.
  • Takahashi, J.S., Zatz, M. (1982). Regulation of circadian rhythmicity. Science. 217 (4565): 1104–11.

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