Shift work and jet lag are two consequences of biorhythm disruption. Discuss the consequences of disrupting biological rhythms. (24 marks)
The interplay between endogenous pacemakers and external zeitgebers is designed to keep physiological processes and behaviours such as sleep-waking cycles and hibernation perfectly in tune with the outside world. Over a year, days gradually get shorter and nights become longer, and activity and physiological processes adjust their cycles to these zeitgebers.
External zeitgebers such as day length change only slowly in the normal course of events, allowing our biological rhythms time to adjust to the changes. However, the increasing complexity of human society has produced situations in which zeitgebers change rapidly, and this can have dramatic effects on biological rhythms and the behaviours they affect. The best examples are shift work and jet lag.
Shift work was introduced with the assembly line and 24-hour working. The traditional pattern would be to divide the 24-hour day into three eight-hour periods, midnight to 8am, 8am to 4pm and 4pm to midnight. Shifts would change at intervals of, for example one week, and the traditional rotation was backwards; one week on 4pm to midnight, one week on 8am to 4pm, and one week on midnight to 8am. Coren (1996) estimated that one in five workers in America are on shift work of one sort or another.
The effects of this are predictable. Many shift workers are operating machinery or making decisions at times when their endogenous pacemaker is completely out of synchronisation with the external world, especially with the light-dark cycle. Apart from effects on performance, this leads to frequent reports of fatigue, depression and illness.
Our body clock prepares us for sleep when it is dark, and particularly between 2am and 4am. It is no coincidence that some of the most disastrous industrial accidents have occurred during this phase of shift work.
Another real life example of this...