Biological Rhythms

A detailed Summary of Biological Rhythms

All plants and animals have endogeous cycles that, in response to an outside rhythm (zeitgeber), will cue various actions. For example, bears know they must hibernate, poinsettias know they must flower and humans know they need sleep. In correspondence with a particular season, length of day, and light intensity respectively, these events will occur. In the example with the poinsettia, the vegetative/flower cycle is synchronized with a day length cycle that has longer hours of darkness, resulting in a chemical reaction that releases florigen and signals to the poinsettia to flower. Similarly, a chemical reaction takes place in humans with their sleep/wake cycle. This will be discussed in the essay along with disorders associated with this cycle.

Humans possess many biological clocks. Depending on the cycle it could be an infradian (longer than a day), ultradian (shorter than a day), circadian (about a day), or circannual (about a year) rhythm. In the case of the human's internal sleep/wake cycle, it's a circadian rhythm. The human sleep/wake cycle is a bit longer than 24 hours (closer to 25 hours), therefore it needs an entraining agent or zeitgeber. This is an external environmental rhythm whic

Seasonal affective disorder (SAD) is the reoccurring depression during a particular season. The occurrence of SAD during the summer months is a very rare condition. Typically, winter is the season when the majority of sufferers feel the onset of SAD. The days get shorter and the nights get longer as the transition from autumn to winter takes place. As said earlier, melatonin production (which occurs during the nighttime) causes you to feel sleepy and less alert and can onset the feeling of depression and irritability.

As infants, our sleep/wake cycle was initially random compared to that of our parents or guardian. Eventually, over the course of 6 weeks, we began to adapt the circadian cycle and after approximately 4 months, we were entrained to the 24-hour cycle. This is due to the external cues of our parents/guardian.

h will keep it in sync with the 24 hour day. The most dominant cycle is the light/dark cycle. However, it's necessary to transmit the external information to the internal cycle so that synchronization is achieved.

re are many scientists who are experimenting with melatonin as a treatment for various sleep disorders and health problems.

Studies show that in the absence of a light/dark cycle or any external cues, humans will still secrete melatonin in the same cyclic manner. This is known as free running and explains why individuals who live in the polar regions of the earth can maintain a 24-hour cycle. However, because our internal clock runs closer towards the 25-hour mark, it will be slightly off to the 24-hour day. Also, in

Some common words found in the essay are:
SCN SCN, Biological Rhythms, sleep/wake cycle, pineal gland, light/dark cycle, outside environment, human sleep/wake cycle, sync outside environment, cycle it's, human sleep/wake, day length, chemical reaction, particular season, vegetative/flower cycle,

Approximate Word count = 1064
Approximate Pages = 4 (250 words per page double spaced)

Category: Science