What about blind people? What happens to their rhythm?
There should also be some discussion of the rhythm in absence of stimuli. There was a study done, though I forget where, which roughly showed that a great deal of mammals naturally act on a cycle of 26-28 hours in the absence of a day-to-night cycle and thrive there stably. I can personally attest to this, in fact, as I pay little attention to the sun and by my own schedule I usually prefer to sleep 12 hours and be awake 15 or so, creating schedule problems.
Blind people will be exactly the same as everyone else. The perception of light is not the same as seeing light. Even if there is a problem with the eyes the body is still able to perceive light, and it knows when it is day and when it is night. The perception of light is simply the input stimulus for the system. From there, a cascade of hormones affect an even greater number of genes, ultimatly setting the clock.
For your second point, there have been several studies done in humans, other animals and especially plants, all concerning circadian rhythms in the absence of light. Currently, the evidence suggests that there is an intrinsic cycling that does occur. I work mostly in plants, and I know for plants that once a cycle is set, moving a plant into total darkness, initially has little effect. The cycling becomes programmed and takes a long time to reset.-- Doucher 18:03, Apr 23, 2005 (UTC)
MrSandman 29 June 2005 19:37 (UTC)
I remembered while I was reading this article one of the few things I picked up from a psychology class - human circadian rhythms are 25 hours rather than the 24 the article claims. Numerous sources easily found through a search engine will confirm this - http://www.sleepdisorderchannel.net/jetlag/ is just one of many. I've edited in a short bit about this to reflect this somewhat counterintuitive fact. 69.92.141.242 08:58, 26 September 2005 (UTC)
Please give a source for the temporarily deleted paragraph:
The paragraph above has been corrected to reflect the idea of a genetically preset circadian period in relation to relatively small amount of published work that addresses this question.
In general, this whole page could do with more references to published work.
October 6, 2006 131.111.8.96
"The SCN does not appear to be able to react rapidly to changes in the light/dark cues." I think that 1) this needs a source, and 2) it is meaningless anyway, as long as "rapidly" is not defined. --Beth (who doesn't really know how to do this kind of thing yet - will try to improve ;-))
I'm very curious about your mention of circadian rhythms in plants. There seemed to be very little detail available. With animals, and even animal cells, there's a noticeable difference in behavior. Specific organs secrete different hormones and such. What exactly is the basis of circadian rhythms in plantlife that can't be explained by the organism immediately reacting to stimuli (like sunlight)? Would the plant behave according to a similar schedule even if sunlight were blocked?
I was a little thrown by the last statement: "Circadian rhythms are thought to have evolved completely independently in cyanobacteria, animals, plants and fungi." So, Circadian Rhythms have evolved independantly of life? No, this statement means that the molecular circadian clock in each of these kingdoms has separate evolutionary origins.
Have there been any studies done on how the day/night cycle affects single-cell organisms? For example, are there nocturnal bacteria?
-Thanks 24.126.178.118
What about blind people? What happens to their rhythm?
There should also be some discussion of the rhythm in absence of stimuli. There was a study done, though I forget where, which roughly showed that a great deal of mammals naturally act on a cycle of 26-28 hours in the absence of a day-to-night cycle and thrive there stably. I can personally attest to this, in fact, as I pay little attention to the sun and by my own schedule I usually prefer to sleep 12 hours and be awake 15 or so, creating schedule problems.
Blind people will be exactly the same as everyone else. The perception of light is not the same as seeing light. Even if there is a problem with the eyes the body is still able to perceive light, and it knows when it is day and when it is night. The perception of light is simply the input stimulus for the system. From there, a cascade of hormones affect an even greater number of genes, ultimatly setting the clock.
For your second point, there have been several studies done in humans, other animals and especially plants, all concerning circadian rhythms in the absence of light. Currently, the evidence suggests that there is an intrinsic cycling that does occur. I work mostly in plants, and I know for plants that once a cycle is set, moving a plant into total darkness, initially has little effect. The cycling becomes programmed and takes a long time to reset.-- Doucher 18:03, Apr 23, 2005 (UTC)
MrSandman 29 June 2005 19:37 (UTC)
I remembered while I was reading this article one of the few things I picked up from a psychology class - human circadian rhythms are 25 hours rather than the 24 the article claims. Numerous sources easily found through a search engine will confirm this - http://www.sleepdisorderchannel.net/jetlag/ is just one of many. I've edited in a short bit about this to reflect this somewhat counterintuitive fact. 69.92.141.242 08:58, 26 September 2005 (UTC)
Please give a source for the temporarily deleted paragraph:
The paragraph above has been corrected to reflect the idea of a genetically preset circadian period in relation to relatively small amount of published work that addresses this question.
In general, this whole page could do with more references to published work.
October 6, 2006 131.111.8.96
"The SCN does not appear to be able to react rapidly to changes in the light/dark cues." I think that 1) this needs a source, and 2) it is meaningless anyway, as long as "rapidly" is not defined. --Beth (who doesn't really know how to do this kind of thing yet - will try to improve ;-))
I'm very curious about your mention of circadian rhythms in plants. There seemed to be very little detail available. With animals, and even animal cells, there's a noticeable difference in behavior. Specific organs secrete different hormones and such. What exactly is the basis of circadian rhythms in plantlife that can't be explained by the organism immediately reacting to stimuli (like sunlight)? Would the plant behave according to a similar schedule even if sunlight were blocked?
I was a little thrown by the last statement: "Circadian rhythms are thought to have evolved completely independently in cyanobacteria, animals, plants and fungi." So, Circadian Rhythms have evolved independantly of life? No, this statement means that the molecular circadian clock in each of these kingdoms has separate evolutionary origins.
Have there been any studies done on how the day/night cycle affects single-cell organisms? For example, are there nocturnal bacteria?
-Thanks 24.126.178.118