Blog #3: The Circadian System

Z by Osato-kun

Okay everyone, gather 'round. The human body is one big system made up of other systems to help the body function well, right? The nervous system is in charge for sensory inputs from various nerves from the body and the muscular system is in charge of the body's movement.
 Now, what system is in charge of telling the body when to sleep and when to wake up? The answer is "The Circadian System." 

In an article written by Akiko Hida, Shingo Kitamura and Kazuo Mishima, Pathophysiology and pathogenesis of circadian rhythm sleep disorders, the human body show a 24-hour pattern based on the light and darkness the person sees, and when the persons eats or food intake. The circadian system is highly dependent of light or the lack of it. If the body's circadian systems become damaged, this could lead to various kinds of diseases, including sleep disorders.

The article states that "The desire to sleep increases gradually with extended wakefulness and decreases during sleep." As stated in the article, the circadian system and the homeostatic drive work together in the body's sleep-wake cycle. The homeostatic drive is the body's way to measure how long the person has been awake. Paired with with the circadian system, it sends signals to the brain that it's time to sleep.

The Circadian system is a complex system that base itself from the environmental factors it can get and judge whether it's time to sleep or not. The body is also able to track down what time of the day it is by assessing the light and food intake of the person. Apart from an abnormal eating pattern, when else do you eat lunch?

In Dijk and Archer's article Light, Sleep, and Circadian Rhythms: Together Again, it shows how the Circadian system is largely dependent on light more than the other sources for the brain to process.The light is gathered by the melanopsin, a photopigment found in the retina, and then sent to the brain for processing. The Circadian system and the homeostatic also influences the major stages in one sleep cycle, namely rapid eye movement sleep or REM sleep and non-REM sleep.

The article continued and stated that "Mounting evidence supports the view that the effects of light on sleep and brain activity during wakefulness, as well as the duration of sleep and the homeostatic response to sleep loss, depend on both melanopsin and circadian time." Namely the circadian system's idea of what time it is and melanopsin are the determiners for the body to be active, to stay awake or to go to sleep.

Melanopsin clearly has a huge role to the sleep cycle and needs to be further researched on, for me.  Melanopsin gathering light for the brain to prcoess that it is still time to stay awake might be factor to why people are sleep deprived as they continue to work in areas that are well lit, also to avoid eye strain from working in the dark. This extended exposure to light could be a factor for people being able to stay active in the late night and leading to the person to be deprived of sleep.