Lecture 2

Question 1

Early Biological Clocks
Studies

Cave studies:
Kleitman and Richardson, 1938

Answer 1

Kleitman’s and Richardson’s Quarters in Mammoth Cave.

– In 1938, to the glare of movie lights, Nathaniel Kleitman and Bruce Richardson emerged from a highly publicized 32-day
sojourn in Mammoth Cave, Kentucky.

– The two researchers tried to switch to a rhythm that was 4hrs longer than the normal 24hr day.

– If they could do so, the normal 24-hour cycle might simply be a reaction to the
surrounding world.

– The results were inconclusive

Question 2

Early Biological Clocks
Studies

Cave studies:
Jurgen Aschoff

Answer 2

– 2 decades after Kleitman’s & Richardson’s study, Jurgen Aschoff, a medical doctor and physiologist, expanded on Kleitman’s human isolation experiments.

– Subjects placed in an underground bunker were allowed to turn lights on or off according to their own internal rhythms.

– Aschoff tracked their sleep-wake cycles, body temperature, urine output, and other physiological and behavioral
variables.

– He concluded that humans, like the plants investigated by de Mairan, have Endogenous circadian cycles.

Question 3

Early Biological Clocks
Studies

Cave Studies Summary

Answer 3

– Both researchers tried to adjust their sleep-wake cycles to a 28hr cycle, with mixed results.

– The use of only 2 people and the failure to recognize that even artificial light could act as a zeitgeber resulted in unclear data.

Question 4

Recent Evidence that Biological Clocks are Endogenous

Answer 4

Animals maintained in constant conditions aboard a spacecraft orbiting far above the earth, and presumably away from subtle geophysical cues, display biological rhythms with periods similar to those observed on earth.

Question 5

NASA has conducted studies
of wake/sleep cycles in
space

Answer 5

…..

Question 6

NASA has also conducted circadian locomotor experiments on insects.

Answer 6

• Darkling beetles were the
subjects of these 1997 NASA/Mir space station
experiments.

• Studies on a variety of species, from single-celled organisms to humans, have shown that changes in Gravity can alter circadian rhythms.
• The device shown on slide is a beetle activity monitor, which is used to measure locomotor activity — a commonly studied circadian variable.

Question 7

SCN Implants Reinstate

Clock Characteristics

Answer 7

????