Circadian Rhythms and the Circadian Organization of Living ...
Circadian Rhythms and the Biological Clock: An Historical Introduction.
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Transcript of Circadian Rhythms and the Biological Clock: An Historical Introduction.
![Page 1: Circadian Rhythms and the Biological Clock: An Historical Introduction.](https://reader035.fdocuments.us/reader035/viewer/2022062423/5697bfbb1a28abf838ca1211/html5/thumbnails/1.jpg)
Circadian Rhythms and the Biological Clock:An Historical Introduction
![Page 2: Circadian Rhythms and the Biological Clock: An Historical Introduction.](https://reader035.fdocuments.us/reader035/viewer/2022062423/5697bfbb1a28abf838ca1211/html5/thumbnails/2.jpg)
Outline
• What are Circadian Rhythms?
• Why do we call the mechanism that regulates circadian rhythms a “Biological Clock”?
![Page 3: Circadian Rhythms and the Biological Clock: An Historical Introduction.](https://reader035.fdocuments.us/reader035/viewer/2022062423/5697bfbb1a28abf838ca1211/html5/thumbnails/3.jpg)
What are the Important Characteristics of a “Clock”?
1. It can be set to local time2. It can tell you the time of day.3. It can be used to measure lapse of time
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A Human Sleep Wake Cycle in the Laboratory
24-h Day
25-h Day
24-h Day
Unscheduled Day
Charles Czeisler
Human Isolation Chamber in Sapporo Japan
Jurgen Aschoff
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Circadian (Circa, Dies) Rhythms are Ubiquitous in Living Systems and Have Similar Properties
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Circadian Rhythms: The Basic Model
+ =
EntrainedRhythm
FreerunningRhythm
Light Cycle
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Origins of the Field of “Chronobiology”: Early Observations of Daily Rhythms in Plants
Scarlet Pimpernel
Day
Night
The first written record: In the 4th century BC Adrosthenes, a scribe for Alexander the Great, wrote that he observed on the march to India that the leave of the tamarind tree always opened during the day and closed at night.
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Jean-Jacques deMairan’s
Experiment (1729)“The progress of true science,
which is the experimental kind, is necessarily slow”
The first hint that daily rhythms are internally driven
Daily rhythms of "sleep movements" of leaves (Mimosa).
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The Next 200 Years
•1832 de Candolle discovers that the Mimosa opens it’s leaves 1-2 hours earlier each day
•1906 Simpson and Gailbraith find daily temperature rhythms in monkeys persist in constant darkness
•1922 Richter shows persistent rhythms of activity in animals (rats)
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The Birds
And the Bees
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Recognizing Local Time of Day
Karl von Frisch
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Daily Rhythms in Nectar Secretion
Daily rhythm of nectar secretion in Hoya carnosa. Matile, P, (2005) Bee visits to a crookneck squash
patch (peak nectar production at 9:00 AM) Edge et al. (2012)
Porcelainflower
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No News to the Poets!
Andrew Marvell (1621-1678)from Thoughts in a Garden
“And as it works, the industrious beecomputes its time as well as we.How could such sweet and wholesome hoursbe reckoned but with herbs and flowers”
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Dance Language of the Bees: Measuring Lapse of Time
The Waggle Dance
Time -Compensate
dSun Compass
Orientation
When a bee finds a food source some distance from the hive, he can return to the hive and, through dance, can communicate the direction (with respect to the sun) and the distance of the food source. The movement of the sun across the sky is compensated for by the bee’s internal, biological clock.
The Round Dance
A vertical waggle indicates directly towards the sun
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Sun Orientation in Starlings
Gustave Kramer 1950Klaus Hoffman 1960
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Circadian Clocks and Sun-Compass Orientation
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“Photoperiodism” and Measuring Daylength
Summer (Long Day)Fall (Short Day)
Garner & Allard, 1920
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Michael Menaker
Photoperiodic Time Measurement in a Hamster
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• Released from the pineal gland at night. In mammals, synthesis and release are controlled by the Biological Clock.
• In many mammals it is involved in regulating seasonal cycles that are controlled by the length of the daily photoperiod (reproduction, coat color, fat accumulation, hibernation, etc.)
Siberian Hamsters from long days/short nights (summer) and short days/long nights (winter). Testes from Long-day and Short-day
hamsters
• In humans melatonin’s function is not yet fully understood, though in the popular press it has been touted as a cure for everything from insomnia to Alzheimer’s disease.
Pineal Gland & Melatonin
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The Problem of Temperature
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Early Studies of Human Circadian Rhythms
http://www.bgamplifier.com/lifestyle/newsreel-sleep-experiment-in-mammoth-cave/youtube_dc3b38ce-f3a9-11e2-b516-0019bb2963f4.html
Siffre’s Cave Experiment in Texas, 1972. He emerged after 179 days, but he thought he had been in the cave for only 151 days