Last Updated 27 Jan 2021

Discuss the Disruption of Biological Rhythms

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Discuss the disruption of biological rhythms 24m One example of disruption of biological rhythms is due to shift work and shift lag. This disrupts your sleeping pattern because it means you are required to be alert at night, so need to sleep during the day. This reverses and disrupts your circadian rhythm, becoming desynchronised where it is no longer entrained by EZ’s. There are many consequences of desynchronisation such as sleep deprivation. Shift workers find it hard to sleep during the day because of the EZ’s such as light and sound disturbances that keep you awake.

This means shift workers find it even more difficult to stay awake at night time because they have had a poor quality daytime sleep. This then affects their alertness. Night workers often experience a circadian ‘trough’ of decreased alertness during their shifts. For example Boivin found that cortisol levels are at their lowest between 12 and 4am, which is the primetime a night worker, would be working. This means they have low alertness and decreases the efficiency of their job. There are also many effects on health due to shift work. A significant relationship has been found between shift work and organ disease.

For example, Knutsson found that people who worked shift work for more than 15 years were likely to develop heart disease than a non-shift worker. This may be due to the direct effect of desynchronisation in the circadian rhythm. Jet lag is another example of how biological rhythms can be adjusted, but their effects are found to temporary, as travelling happens once in a while, whereas shift work may be somebody’s job which they have to be doing constantly every day. However, our biological rhythms are not equipped to cope with sudden and large changes in our rhythms.

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It has been found that they need approx. 1 day to adjust as each time zone is crossed. This is because the dorsal portion of the SCN needs several cycles to fully resynchronise, as it is less sensitive to light. When the dorsal portion of the SCN is adjusting we experience disruption in the form of jet lag. It has been found that it is easier to fly from east to west, as you need to stay up later, so your biological rhythms can adjust by you getting more sleep in the morning, whereas west to east you must wake up earlier so is harder to adjust.

This can be demonstrated in a study where an American baseball team who travelled west to east saw their wins drop 37% due to phase advance where they have to get up earlier in the morning, causing a reduction in their overall performance. There are many real world applications that have derived from the effects of shift work and jet lag, enabling people to live alongside these disruptions in their biological rhythms. These are mainly targeted at shift work. It has been found that lorry drivers are prone to falling asleep at the wheel on night shifts.

Legislation has been put in place to prevent this from happening. They now have a monitor in the cars that produce a sound telling the driver when they should have a nap to ensure they are not sleep deprived and avoid accidents from occurring. It has also been found that people should have bright lights at their work on a night shift to act as an EZ overriding the endogenous pacemakers. This could be supported by Gronfier’s study which found circadian rhythms were able to be entrained longer than 24 hours by using bright light pulses known as modulated light exposure.

However, Boivin found that artificial lighting is only moderately effective in overriding the rhythm. Dim lighting which is mainly used in places such as hospitals failed to keep participants awake. This may be because the pineal gland is detecting an absence of light meaning melatonin is being produced which induces sleep. Therefore, in response to this research nurses who work in hospitals should have bright lights around the workplace to keep them awake. Melatonin has been found to be a ‘miracle cure’ for shift lag and jet lag. This is the hormone that induces sleep.

This means that people experiencing sleep disruption can take melatonin tablets in order to sleep during the day or when they have finished their shift. This is supported by Herxheimer and Petrie who found when melatonin was taken near to bed time it was very effective. However, if melatonin was taken at the wrong time of day it could delay their adaptation to changing sleep patterns. However, these two explanations and examples of sleep disruption may be reductionist as it fails to ignore other factors that may disrupt the person’s sleep patterns.

The lack of sleep may be associated with them having to go to bed at unusual times. This may lead to the person experiencing social disruption as they find it difficult to meet with their friends or spend time with their family. This may lead to high cortisol levels as they are stressed with the lack of social interaction. High cortisol levels may be intervening with their sleep quality making them sleep deprived. Therefore, there are other intervening factors other than going to bed in the daytime.

This can also be displayed in jet lag, where social customs are involved in entraining the biological rhythms. When you are travelling you are encouraged to eat and sleep at the same time as the country you are in. This could also help reduce symptoms of jet lag such as nausea. Timing of meals can re set the biological clock in the liver. Eating at the same increases enzyme production at the right time for digestion and avoids stomach upset leading the nausea.

Therefore, social customs are an important factor to consider in the effects of sleep disruption and how they play a major role. The effects of disruption of circadian rhythms can vary considerably between different individuals. Some people may have circadian rhythms that try to adjust and change in response to shift work or jet lag, or other people’s circadian rhythms which don’t change at all. Reinberg found that people who gave up shift work because they couldn’t cope had constantly changing rhythms, whereas ‘happy shift workers’ had rhythms that didn’t change at all.

This suggests that it may not be the shift work itself that is causing the sleep deprivation; it may be due to individual’s circadian rhythm and its ability to adjust or cope in different rhythms. Therefore, people’s who’s rhythms changed constantly may have experienced imbalance in neurotransmitters or raised cortisol levels from stress, meaning they experienced sleep deprivation. It would have to be asked whether shift work and jet lap is a disruption in biological rhythms for every individual, or whether some people are able to cope without the rhythm trying to adapt at all.

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