Biological rhythms: definition, types and functioning

Biology seems to have a pre-assigned role for every moment of our existence.

Surely all of us have heard at some point in our lives that people are creatures of habit. This expression, besides being true, hides a myriad of processes that our body performs to keep these habits in check.

These processes make reference to Biological rhythmswhich 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 our eyes.

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 a chronometer or internal clock and external or environmental variables that intervene in their synchronization.

Habits and activities, both human and animal, always present a regular cadence and harmony. So to speak, living implies a rhythmic phenomenon that marks us when to eat, when to drink, when to sleep, etc.

In this way, if we stop to think about the relationship between a bodily habit or custom and its relationship with time, we can observe that all of them take place in the same rhythm.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 of it, which is in charge of regulating them.

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

The main internal structures involved in this regulation 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 cardiac rhythms or breathing times, these other types of 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..

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 bodily needs or habits that occur approximately every 24 hours. approximately every 24 hours.

The best known and most illustrative example is sleep cycles. Usually the need for sleep always appears at the same times and any alteration of this rhythm sometimes implies some kind of sleep disorder.

If we take this example into account, it is not unusual to think that these habits depend to a large extent on external regulating agents such as daylight. Hence, it is always recommended to sleep in complete darkness because even artificial light can alter our sleep cycles.

Such is the influence of these exogenous regulators that they even influence the course of some diseases or psychological conditions. In the case of depressive disorder, it is common for people to report a worsening of psychological symptoms during the first hours of the day, which 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, i.e. less than once a day.. Although this may seem strange, there are certain bodily habits that work with these oscillations.

The most common example is the menstrual cycle, which is completed once every 28 days. Other phenomena that occur with a cadence similar to that of the menstrual cycle are the lunar cycles and the tides, hence 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 are a series of rhythmic movements that occur with a frequency of more than one every twenty-four hours.

These rhythms are the beating of the heart, blinking, the rhythm of breathing, or REM cycles of sleep which occur every 90 minutes.

How to maintain biological rhythms

As mentioned above, since these biological rhythms are conditioned by numerous external and environmental factors, they can easily be altered as a consequence 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 mood, changes in appetite, etc.), it is advisable to maintain a daily routine that allows us to maintain our energy. it is convenient to maintain a daily routine that allows us to keep our energy.

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

1. Get up and go to bed at the same time.

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

However, it is also necessary to get a minimum number of hours of sleep. That is to say, if one day 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 getting up too early just to keep to the schedule.

2. Maintaining routine even on vacation

Although it may seem unappetizing, it is advisable to maintain our usual schedules even during the vacations.. In this way we will keep our biological rhythms practically intact and it will be much easier to conserve energy once the holidays are over and we have to return to the routine.

If necessary, it is possible to keep a relatively structured schedule, planned in advance, so that the increase in free time does not cause us to postpone tasks whose regularity must be promoted.

3. Always eat at the same time

Like sleep, the sensation of hunger is also subject to a temporal cadence.. Moreover, all biological functions depend on how we nourish ourselves and when we do so, so that failures in nutrition and in the regularity with which we eat can create a chain effect. Therefore, it is essential to maintain stable schedules for the main meals. In this way, we will control the sensation of hunger and avoid binge eating.

4. Keep an agenda or diary with our habits

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

Bibliographical 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.