Circadian Rhythm

At its essential core, sleep is a series of patterns. It is broken up into stages of sleep that collectively form a sleep cycle. This sleep cycle is cyclical in nature in and of itself, and its repetitive nature essentially forms a person's overarching sleep interval.

However, this sleep interval is not something that is independent. Rather, it is part of an overall process that is known as a circadian rhythm; a biological process that displays an endogenous, entrainable oscillation over the course of around 24 hours.

A Look at the 'Body Clock'

The prime mover behind the circadian rhythm is a circadian clock, also known as a circadian oscillator. In essence, this acts as internal .body clock;. as it is a biochemical mechanism that moves to and fro in conjunction with a 24 hour period. There are three major components that collectively comprise a body clock and the way in which it functions:

  1. A central oscillator within a period of around 24 hours that keeps time.
  2. A series of input pathways that links to the central oscillator in order to enable rhythmic physiological or behavioral events to synch up to a specific period and phase.
  3. A series of output pathways that are linked to distinct phases of the oscillator that are tied to the regulation and control of concrete rhythmic processes pertaining to biochemistry, physiology, and behavior.

These components, when viewed collectively, essentially dictate a pattern within a person that is built around a 24 hour time frame. In the case of sleep, they set the internal function that establishes the pattern of when a person is going to be awake or asleep.

External Influences

If a person's circadian clock was isolated in a vacuum and not influenced by any sort of exterior force, it would be able to work independently and set its own waking and sleeping parameters. For this reason, circadian rhythms are considered to be endogenous (that is, built-in or self-sustained). However, the rhythms are molded and shaped - a process that is known as entrainment - to match the patters that are dictated by various outside forces and external cues in the environment. These cues, which are known as zeitgebers, works to not only synchronize the biological rhythms of a person to the earth's 24 hour time period, but also to its 12 month annual cycle.

The most important, if not obvious, of these particular cues is linked to daylight. The circadian rhythms that have develop because of the earth's natural 24 hour light/dark cycle typically dictates that the process of wakefulness happens during the day and the process of sleep happens during the evening. However, the light/dark cycle is far from the lone zeitgeber that influences a circadian rhythmic pattern. Other factors pertaining to temperature, levels of social interaction, and eating and drinking patterns all can play a hand in how a person's circadian rhythm can get established.

Circadian Rhythm Criteria

In order for a biological rhythm to be considered circadian in nature, it must adhere to three general elements. The first element is that it needs to be an endogenous free-running period lasting around 24 hours, and can run in this manner independently of outside influence. The second element is that the rhythms are entrainable through exposure to various outside stimuli, such as heat and light. The third element is that the rhythms display temperature compensation. What that means is, the rhythm must be able to withstand the broad range of internal temperatures that are found within the body without producing an alteration in the rhythm.

Circadian Rhythms on a Biological Level

According to scientific study, the circadian clock that is found in people is regulated by a specific part of the brain known as the Suprachiasmatic Nucleus, otherwise known as SCN. This nucleus is a group of cells that are located within the hypothalamus, and is charged with regulating the response to light and dark signals. The response is triggered via the optic nerve of a person's eye; when light is registered by the optic never, light then travels to the SCN, which in turn signals the body clock to be awake. Congruently, the SCN signals other various parts of the brain that are charged with the regulation and control of certain hormones, body temperature and other functions that are ultimately linked to making a person feel sleepy or awake. The SCN also responds to light by halting the release of melatonin; a hormonal secretion whose expression triggers the onset of sleep.

The circadian rhythm ultimately plays a very important part to a body's inherent functionality. It has been shown that during a person's sleep cycle - particularly during instances of deep sleep - several anabolic functions occur. These functions pertain to the regulation and control of several key processes that are designed to keep the body within a state of homeostasis. Some of these regulatory processes include proliferation of muscular and skeletal tissue, immune system functionality, and muscle and tissue repair. The circadian rhythm works to ensure that these important functions are occurring on a nightly basis, and at a predictable time interval. Without this process in place, the pattern of the boosted processes that pertain to maintaining basic levels of homeostasis would be disrupted, which could ultimately have a negative impact on the body in general.

All matters of homeostasis aside, it has been shown that a disruption to a circadian rhythm in general has a negative impact. This is why travelers tend to experience jet lag when they go on long trips. The shift in several different zeitgebers such as light and time forces the brain to inform the body to entrain in order to cope with the new environment and their parameters. On a smaller scale, similar disruptions can occur when a person chooses to keep hours that are long and irregular to the typical pattern as dictated by the circadian rhythm.

Ultimately, the main mandate that is derived from the presence of the circadian rhythm is to listen to what your body is telling you, when it is telling you. Paying attention to such signaling will play an important role in maintaining your overall health and well-being.