The Circadian Rhythms

14. Evolutionary theories often emphasize that humans have adapted to their physical environment. One such theory hypothesizes that people should spontaneously follow a 24-hour cycle of sleeping and waking—even if they are not exposed to the usual pattern of sunlight. To test this notion, eight paid volunteers were placed (individually) in a room in which there was no light from the outside and no clocks or other indications of time. They could turn the lights on and off as they wished. After a month in the room, each individual tended to develop a steady cycle. Their cycles at the end of the study were as follows: 25, 27, 25, 23,24, 25, 26, and 25.

Circadian rhythms occur every 24 hours; an example of a circadian rhythm is the sleep-waking cycle. We are diurnal animals who are active during the daytime and asleep at night, other animals are nocturnal they are active at night but asleep during the day. The circadian rhythm depends on the interaction of physiological and psychological processes to be tuned into the sleep-waking cycle so energy is provided when needed. As diurnal humans we have a fairly stable sleep pattern with the time we go to sleep and the time we wake up, this consistency suggests an internal mechanism controls sleep, endogenous pacemaker. However, this can be overridden by external factors, exogenous zeitgebers.

Russell Foster is a British professor and a circadian neuroscientist at Brasenose College. He studies the sleep cycles of the brain. He and his group were credited for discovering photosensitive ganglion cells in the mammalian retina. This discovery will help to find more information about the circadian rhythm system. In 1980, Foster graduated from the University of Bristol with a degree in Zoology. He has earned many awards for his work and is also the author of a few books.

Humans have a natural rhythm of 25 hours of sleep and wakefulness, in order to reset this the brain plays an important role with the suprachiasmatic nucleus which is a cluster of neurons in the medial hypothalamus of the brain. The SCN

Circadian rhythm disorder is related with people's biological clock. It means you people find difficulty falling asleep or often keep awake at the sleep time. Actually, you have some problems about sleep disorder.

The photoperiodic hypothesis proposes that individuals with SAD are similar to photoperiodic mammals in such a way that they have retained this primitive biological mechanism for tracking changes in photoperiod, a circadian signal of change in season, that individuals without SAD do not have (Rohan,

1. An example of this would be our response to light. We follow a circadian rhythm of being awake in the daytime, and sleeping when it is dark outside.

In life, we all encounter those night where we can’t seem to get to sleep. This can be due to insomnia or having a lot of things to do and little time to do them. During college and afterwards people will begin to deal with a lack of sleep more and more as they gain more responsibilities. I’ve always heard it’s not good to go without sleep and I agree with this thought. This was confirmed when we had a lecture on consciousness. We discussed how our sleep and wake schedule, biological clocks, bodily functions, etc., are controlled by circadian rhythms (Truelove, 2017).

The pineal gland also plays a key role in regulating animal circadian rhythms, which vary across species. Melatonin is synthesized from serotonin by N-acetyltransferase. In mammals, N-acetyltransferase activity is stimulated in the CNS by sympathetic nerves stemming from the superior cervical ganglion, whereas in birds, the N-acetyltransferase “control switch” appears to lie within the gland itself (Deguchi, 1979).

Sleep duration and quality participate in normal metabolism, function of immune system, mood, and cognitive functioning [1]. Short duration of sleep and circadian misalignment are hypothesized to contribute to many problems of health including over weight, diabetes, metabolic syndrome, cardiac disease, mood disorders, cognitive dysfunction, and

A misconception that people have regarding delayed sleep phase disorder is that as long as the human body retains six to eight hours of sleep per day, then they should be fully functional no matter when they fall asleep. However, after researching delayed sleep phase disorder, it was clear to see that this disorder affects a person’s social life more than their sleeping schedule. While they are asleep during the day, or during other hours that most of the general population actively socializes, the individuals with the disorder are lacking social involvement and instead trying to retain the recommended hours of sleep. This disorder can lead to fatigue, excessive sleepiness during the day, and disconnection from family and social life 3. Although the lack of social involvement is seen this disorder further affects the body internally such as manipulating the genes that work with the circadian rhythm this affecting the body’s processes, influence gene expression, make the immune system significantly weaker, and the glutamatergic process 1,2. Resetting the circadian clock is not an easy task, but there are possible techniques and treatments for patients with this disorder. The difficulty to reset the circadian clock is explained in a study 2 of people who suffer from neurological

In vertebrates, melatonin is synthesised in the pineal gland (Foulkes et al. 1997). In mammals however, the pineal cells found within the gland are not light reactive nor do they have a circadian clock imbedded inside (Foulkes et al.

Sleep is undeniably a necessity for humans and other animals alike. At the beginning of each day, our bodies awake like clockwork in conjunction with the rising sun. Then, at day’s end, they begin to wind down into sleep until the morning. While there certainly may be plenty of mysteries revolving sleep that have yet to been unraveled, from all the way up until now and for centuries to come, it is evident that sleep should hold priority in the schedules of all people. Yet, despite all of this being true, sleep is consistently being taken for granted. And, it is not an overgeneralization to say that many people have, at least once, trudged through a late night as many people have. Even to the point of the night no longer being considered “a

Aside from noticing night and day and clocks our body has its own system to tell us when to sleep and when to wake, our circadian rhythm. The human body naturally runs on a twenty five hour clock, so living on a twenty four hour schedule is often hard on the body because it loses an hour each day. On top of this natural loss most people do not get the right amount of sleep each night which can cause a whole host of problems. This is part of

 Jet Lag: internal biological clocks collide with external clocks as a result of moving across several time zones.