1. Circadian Rhythms and the Biological Clock: An Historical Introduction

2. Outline What are Circadian Rhythms? Why do we call the mechanism that regulates circadian rhythms a “Biological Clock”?

3. What are the Important Characteristics of a “Clock”? 1.It can be set to local time 2.It can tell you the time of day. 3.It can be used to measure lapse of time

4. 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

5. Circadian (Circa, Dies) Rhythms are Ubiquitous in Living Systems and Have Similar Properties

6. Circadian Rhythms: The Basic Model + = Entrained Rhythm Freerunning Rhythm Light Cycle

7. Origins of the Field of “Chronobiology”: Early Observations of Daily Rhythms in Plants Scarlet Pimpernel Day Night The first written record: In the 4 th 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.

8. 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).

9. 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)

10. The Birds And the Bees

11. Recognizing Local Time of Day Karl von Frisch

12. 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

13. 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 hours be reckoned but with herbs and flowers”

14. Dance Language of the Bees: Measuring Lapse of Time The Waggle Dance Time - Compensated Sun 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

15. Sun Orientation in Starlings Gustave Kramer 1950 Klaus Hoffman 1960

16. Circadian Clocks and Sun-Compass Orientation

17. “Photoperiodism” and Measuring Daylength Summer (Long Day) Fall (Short Day) Garner & Allard, 1920

18. Michael Menaker Photoperiodic Time Measurement in a Hamster

19. 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

20. The Problem of Temperature

21. 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