Disruption of biological rhythms

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Disruption of biological rhythms


          Where our biological clock has become desynchronised from our external zeitgeber. Physiological cues (e.g. body temp, sleep/wake cycle) desynchronised from external cues (light, meal times).

          Examples - Jet lag and shift work

Jet lag

          Plane travel has become common but can be a problem when your biological clock tells you it is one time but local cues tell you it is another.

          EG: fly to New York from London, leave at midday, takes 7 hours. Arrive 7pm London time which is 2pm NY time. 4 hours later, your body says bed, NY time says party!

          = JET LAG



          Difficulty with concentration & attention



          Can last few hours or few days

          Worse travelling West to East, than East to West. No prob going N to S!

Phase delay

          East to West travel

          Our biological clock is ahead of local time and has to ‘wait’ for external cues to catch up.

Phase advance

          West to East travel

          Biological clock is behind local time and has to move forward to ‘catch up’.

          Phase advance seems to be harder to adjust to than phase delay.

How do we get over jet lag?

          Our SCN (influenced by light entering the eye) needs  to adjust to the changed time in the new place.

          Can take several days

          Significant individual differences.


          Occasional travellers (e.g holiday makers) vs cabin crew studies.


        Recht et al (1995), followed baseball team for 3 yrs. They won 37% games when going W to E (phase advance) & 44% when going E to W (phase delay). This was statistically significant

        But lots of methodological problems (ability of different teams, fluctuations in form, injury). So low validity.

        Support from American servicemen study – more jet lag when going from Europe to USA (3 days), than USA to Europe (8 days).

Cabin crew studies = Regular exposure

          Found to have raised levels of stress hormones & do less



good notes

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