Circadian Rhythms -A-Level Psychology

Biological Rhythms-distinct patterns of changes in body activity that conform to cyclical time periods.

These are regulated by 2 factors:

1)Endogenous pacemaker-internal body clocks e.g. SCN

2)Exogenous zeitgebers-external changes in the environment e.g. social cues,light

Some of these rhythms occur many times a day (ultradian rhythms),others take longer than a day to complete(infradian rhythms).
Circadian rhythms-a type of biological rhythm that is subject to a 24 hour cycle.These regulate the sleep/wake cycle as well as core body temperature.

The sleep/wake cycle:

The fact that we feel drowsy at night and alert during the day demonstrates the effect of daylight(exogenous zeitgeber)

Case study-Siffre’s Cave Study:

He spent several extended periods underground to study the effects on his own biological rhythms

He was derived from natural sunlight and sound but had adequate access to food and drink.

His “free running” biological rhythm stretched to about 25 hours though he slept and woke up at a regular schedule.

This supports the assumption that endogenous pacemakers exert an influence on circadian rhythms.

Case study-Folkard et al 

It lasted for 3 weeks and was located in as dark cave.

12 people went to sleep at 11:45pm and woke up at 7:45pm .

The researcher  sped up the clock so a day eventually lasted 22 hours.Only one person adjusted to this timing.

This suggests that the existence of a strong free running circadian rhythm that can not  be easily overridden by changes in the external environment.

Evaluation Points:

Practical application to shift work-Shift work has been found to lead to desynchronization of circadian rhythms and can lead to adverse and physiological effects.Research by Boivin et al showed that night shift workers suffer a concentration lapse at 6am (a circadian trough) which increases the likelihood of accidents.This research has many economic implications in terms of maintaining worker productivity and preventing accidents in the workplace. Knutsson’s research showed that there is a relationship between shift work and poor health;shift workers are more likely to  develop heart disease perhaps due to the stress of adapting to different sleep/wake patterns and lack of poor quality sleep during the day.
Pharmacokinetics-is the action of drugs on the body and how well they are distributed and absorbed.Circadian rhythms coordinate a number of the body’s basic processes such as heart rate,digestion and hormone levels.Research into circadian rhythms has revealed that there are certain peak times during the day or night  where drugs are most effective.This has led to the  development of guidelines to do with the timing of drug dosing for a range of medications e.eg antiepileptic drugs(Baraldo).