- Phase response curve
An understanding of how light and temperature pulses perturb circadian oscillation systems is very essential in the analysis of circadian systems entrainment. When light or temperature pulse of a given intensity falls in a specific phase in a free running oscillation, it can generate some phase advances in the preceding activity. When a pulse of light falls at some phases, it can cause phase delays. A phase response curve is therefore a plot of phase changes both in magnitude and sign expressed as a function of the perturbed oscillation phase (Pavlidis, 1973).
The data of the response curve provided indicate that the data must have been collected over a couple of days where the subjects were exposed to three hour of light during subjective daytime and subjective nighttime conditions. The organisms must have been free running prior to the exposure to light pulses. Light pulses of a given intensity falling on certain phase of free running oscillations are the ones that generate either phase advances or phase delays in the preceding activities (Saunders, 1977).
The light pulses in this experiment-generated phase delays and phase advances indicating that the organisms had free running oscillations before the experiment started. A phase delay occurs after light exposure during the first half of the organism daytime exposure, while the phase advances occurs during the second half of the organisms subjective Nighttime (Saunders, 1977).
Ii) Combating Jet Lag
The flight from New York to London takes an average of seven hours twenty minutes
During take off at 20: 00 GMT in New York, it will be already evening, there should be no precautions made regarding exposure to sunlight as light exposure during the first phase of subjective daytime does not cause phase delays or phase advances. However, on arriving in London, it will be 4:20 AM at night. Any exposure to light pulses at this time can result in phase advances in the subsequent activities because it is the second phase of the night. Any exposure to sunlight at this time should be avoided to avoid the development of jet lag.
References
Pavlidis T., (1973). “The free run period of circadian rhythms and phase response curves”.
The American naturalist. Vol 107. No 596.
Saunders, D.S. (1977). An introduction to biological rhythms. Blackie, Glasgow, London.
