An Historical Introduction Outline What are Circadian Rhythms Why do we call the mechanism that regulates circadian rhythms a Biological Clock What are the Important Characteristics of a Clock ID: 600823
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Slide1
Circadian Rhythms and the Biological Clock:
An Historical IntroductionSlide2
Outline
What are Circadian Rhythms?
Why do we call the mechanism that regulates circadian rhythms a “Biological Clock”?Slide3
What are the Important Characteristics of a “Clock”?
It can be set to local time
It can tell you the time of day.
It can be used to measure lapse of timeSlide4
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
AschoffSlide5
Circadian (Circa, Dies) Rhythms are Ubiquitous in Living Systems and Have Similar PropertiesSlide6
Circadian Rhythms: The Basic Model
+
=
Entrained
Rhythm
Freerunning
Rhythm
Light CycleSlide7
Origins of the Field of “Chronobiology”: Early Observations of
D
aily
R
hythms in Plants
Scarlet Pimpernel
Day
NightThe 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.Slide8
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).Slide9
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)Slide10
The Birds
And the BeesSlide11
Recognizing Local Time of Day
Karl von FrischSlide12
Daily Rhythms in Nectar Secretion
Daily rhythm of nectar
s
ecretion in
Hoya
carnosa
.
Matile, P, (2005)
Bee visits to a crookneck squash patch (peak nectar production at 9:00 AM) Edge et al. (2012) PorcelainflowerSlide13
No News to the Poets!
Andrew Marvell (1621-1678)
from
Thoughts in a Garden
“And
as it works, the industrious bee
computes its time as well as we.
How could such sweet and wholesome hoursbe reckoned but with herbs and flowers”Slide14
Dance Language of the Bees: Measuring Lapse of Time
The Waggle Dance
Time -CompensatedSun 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 sunSlide15
Sun Orientation in Starlings
Gustave Kramer 1950
Klaus Hoffman 1960Slide16
Circadian Clocks and Sun-Compass OrientationSlide17
“Photoperiodism” and Measuring
Daylength
Summer (Long Day)
Fall (Short Day)
Garner & Allard, 1920Slide18
Michael
Menaker
Photoperiodic Time Measurement in a HamsterSlide19
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 & MelatoninSlide20
The Problem of TemperatureSlide21
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