Circadian Rhythms Flashcards
Outline biological rhythms
Governed by 2 things:
Endogenous pacemakers - body’s internal biological ‘clocks’
Exogenous pacemakers - external changes in environment
Types:
Ultradian rhythms - occur many times during day
Infradian rhythms - take longer than day to complete
Circadian rhythms - last for around 24 hours, e.g. sleep/wake cycle
Outline the sleep/wake cycle
Governed by endogenous pacemaker - suprachiasmatic nucleus (SCN)
SCN lies just above optic chiasm - provides info from eye about light
Exogenous zeitgebers (light) can reset SCN
Outline Siffre’s cave study
Spent several extended periods underground to study effects on own biological rhythms
Deprived of exposure to natural light & sound, Siffre resurfaced in mid-September 1962 after 2 months in southern Alps cave believing it was mid-August
His ‘free running’ biological rhythm settled down to just beyond usual 24 hours (25) though he continued to fall asleep & wake up on regular schedule
Evaluate circadian rhythms
Strength - SHIFT WORK - Understand adverse consequences when CR are disrupted
E.g. - Knutsson (2003) found relationship between shift work & poor health: 3x more likely to HD than people working regular shift patterns. Boivin (1996) found shift workers xp reduced concentration around 6am (circadian trough) - accidents more likely
Ex. - Research into sleep/wake cycle have real-world economic implications of how best to manage worker productivity
Strength - MEDICAL TREATMENT
E.g. - Led to field of chronotheraputics - medical treatment administered corresponding to person’s bio rhythms. Aspirin treating heart attacks most effective taken last thing at night, as they’re most likely to occur in morning.
Ex. - Cicradian research can help increase effectiveness of drug treatments
Limitation - INDIVIDUAL DIFFERENCES - Generalisations difficult
E.g. - Studies like Siffre based on very small samples - sleep/wake cycles vary widely from person to person. Czeisler (1999) found individual differences in S/W cycle varied from 13-65 hrs. Even Siffre (1999) found his own S/W cycle slowed down since he was young
Ex. - Difficult to use research data to discuss anything more than averages, which may be meaningless
