biological rhythms - circadian rhythms

what are the four biological rhythms

1. infradian

2. circannual

3. ultradian

4. circadian

what is an infradian rhythm

biorhythm with a frequency of less tha one cycle in 24 hours

what is a circannual rhythm

type of infradian rhythm that occurs yearly

what is an ultradian rhythm

biorhythm with a frequency of more than one cycle in 24 hours

what us a circadian rhythm

biorhythm with daily frequency

example of infradian rhythm

menstrual cycle

example of circannual rhythm

seasonal affective disorder

example of ultradian rhythm

stages of sleep

example of circadian rhythm

sleep/wake cycle

Circadian rhythm AO1

• type of biological rhythm subject to a 24 hour cycle which regulates a number of body processes 

• for example the sleep/wake cycle and changes in body temperature 

• case study of Michael Siffre

• research by Aschoff and Wever 

• research Folkard 

outline case study of Michael Siffe

• spent several extended periods underground to study the effects on his own biorhythms

• he was deprived of exposure to natural light but access to food and water 

• after spending two months in a cave he emerged thinking it was mid-August when it was actually mid september

• this was because his free-running biorhythm settled down to one that was around 24.5-25 hours 

outline the research by Aschoff and Wever

• pps spent four weeks in a WW2 bunker where they were deprived of natural light

• most emerged with circadian rhythms lasting between 24 and 25 hours

• although one had a circadian rhythm of 29 hours

• suggesting that our sleep wake cycle is slightly longer than 24 hours

• however this shows that zeightgfabers such as light are important because the clock was not perfectly accurate

outline research of Folkard et al

• 12 pps agreed to live in a dark cave for three weeks

• they returned to b ed when clock said 11:45pm and rose at 7:45am

• unbeknown to the pps researchers gradually sped up the clock so that a 24 hour day only lasted 22 hours

• shows that circadian rhythms can only be guided to a limited extent by exogenous zeitgebers

• however, there are acceptors and individual differences need to be taken into account

what are the evaluation points

1. shift workers

2. issues with cause and effect

3. positive implications in drug efficiency

4. individual differences

evaluation - shift workers

P: knowledge of circadian rhythms has been beneficial in improving the conditions of shift workers

E: Bolvin ett al found workers experience a circadian trough at around 6am where accident are more likely due to lack of concentration

E: additionally Knuttson found that shift workers were 3x more likely to develop heart disease 

L: this is useful as it can inform companies about how to reduce risks associated with shift work and ultimately improve productivity 

evaluation - cause and effect

P: studies investigating the effects of shift work tend to be correlational

E: this means it is difficult to establish whether desynchronisation of the sleep/wake cycle is actually the direct cause of negative effects

E: Solomon concluded that high divorce rates might be due to the strain sleep deprivation places on marriages

L: therefore suggesting the negative effects are caused indirectly rather than directly by shift work

evaluation - drug effectiveness

P: research into circadian rhythms has also had positive implications in the area of drug efficiency

E: as the body goes through a circadian cycle various bodily processes and chemical will be altered

E: therefore there are times of the day when a clinical drug will have greater effect - e.g aspirin should be taken at night to ensure people with heart problems are protected in the mornings when BP is at its highest

L: guidelines have now been developed clearly stating timing of drug dosages to ensure maximum efficiency

evaluation - individual differences

P: all of the research mentioned earlier involves either individual cases or small groups

E: Czerisler found variations in individuals sleep/wake cycle from between 13 to 65 hours

E: additionally Duffy found that osme people have a natur5al preference for going to bed early and rising early (larks) and others the opposite (owls)

L: meaning any conclusions drawn are based on averages with no account for individual variations on the sleep/wake cycle