Circadian Rhythm and Sleep

When you feel fatigued due to things such as jet lag or working rotating shifts, what you are actually feeling is an interruption in your circadian rhythm. Circadian is taken from the two Latin words, circa and diem, which means about a day. When we think about the body and sleep, a day refers to one 24 hour period.

In addition to being linked to a person's sleep patterns, circadian rhythm also affects other things, such as body temperature, blood pressure, and the way the body produces hormones. These things all work in conjunction to let the body know when it should be sleeping and when it should be awake. It also affects how our mood is at certain times.

Many things in nature operate on some kind of rhythm. An example of this would be the earth's rotation. 24 hours is represented by one rotation of the earth. This also comes into play as the seasons change from spring to summer to fall and then to winter. This being the case, animals are affected by circadian rhythm as well. This type of rhythm is best seen in migratory birds as they change their locations with the seasons every year.

Light and temperature are the two main factors that affect the sleep-wake cycle. Things such as your eating schedule and the sound of your alarm clock can also affect circadian rhythm. For women, the menstrual cycle also comes into play.

There is sort of an internal clock in the part of the human brain called the hypothalamus that affects circadian rhythm. The Suprachiasmatic nuclei, or SCN, is made up of two large clusters of neurons that are located on either side of the brain. This is considered to be the master clock of the body. This is one of the tools that the body uses to keep track of time. The way these neurons interact with certain hormones and chemicals is how the body knows when it's time to do certain activities, such as fall asleep, wake up, eat, and others.

This is how circadian rhythm works when it comes to how we sleep. The body will begin to produce certain hormones and neurotransmitters, such as serotonin and cortisol when the first light of day appears. This is how the body knows to begin raising the temperature and blood pressure to begin the waking cycle. Similarly, at the end of the day, the body will know to begin lowering these things when it begins to produce melatonin. This tells the body it's time to fall asleep.

These hormones and neurotransmitters are released at the proper times when the body's circadian rhythm is functioning properly. Problems such as various sleep disorders and emotional problems can occur if the rhythm is off balance. It often takes some time to restore the balance of this rhythm, and get back to a healthy and restful sleep cycle. Keeping the release of these chemicals on time is the key to maintaining a good sleep pattern.

         

Intro to Sleeping Well

Different Stages of Sleep Cycle
How Much Sleep Do We Need
Melatonin and Sunlight