The Physiology of Night Shift – Circadian Rhythm

Define circadian rhythm and discuss schedules of work that would allow the night hours to be covered, but may be better suited for human circadian rhythm.

Circadian Rhythms

Circadian is a Latin term made up of two words; circa which means about and dia, day. Circadian rhythms refer to bodily rhythms that vary periodically throughout during the day. These cyclic changes in psychological and physiological functions are a response to stimuli which is light and darkness in organism’s environment. Research has by greater extent discovered the complexities of these factors; the rhythms have both endogenous components; they are regulated by body clock and exogenous components. Exogenous component is made up of various facets known as zeitgebers. Most powerful zeitgebers is the day cycle; light and darkness (Pittendrigh, 1960).

Understanding   circadian rhythms is instrumental in helping us treat sleep disorders and other health related problems that arise as part of malfunctioning of these rhythms. Circadian rhythms affect sleep-wake cycles. This translates in sleeping disorders. As well, they influence hormonal secretion and body temperature. When we talk of their influence on sleep one may tend to ask how our bodies know when to go to bed. Circadian rhythms are informed by biological clocks. Biological clocks are specialized groupings of molecules found in the body cells. A master clock in the brain coordinates and controls all body clocks working in synch. Circadian rhythms have genetic codes that direct these cyclic fluctuations in man, insects; fruit fly, fungi and rodents.

Circadian rhythm disorders are abnormalities in the internal body clock in determining the length, timing with an inflexibility in response. The body clock adapts slowly to rapid transitions in instances of shift in different schedules. When this happens a condition referred to as desynchrony occurs. Desynchrony is misalignment of the circadian rhythms responsible for sleep and wakefulness, body temperature and hormonal changes. This effects in insomnia, lack of alertness, poor performance and body fatigue due to changes in hormones which impact negatively on an individual’s health.

Circadian rhythm determines sleeping patterns. It is observed when one sleeps or wakes in the normal 24hrs characterised by light and day cycle. This can help explain the causes for jetlag. Jet lag occurs due to circadian disharmony, where circadian rhythms are disrupted due to difference in latitudes of time zones. A traveller flying from California to New York may feel bleary and disoriented as the body clocks is 3 hours behind, so when one wakes at 7 am the internal body clock thinks its 4.00 am. The adjustment may take a few days for the alignment (acclimatization) with the new environment (Pittendrigh, 1960).

These biological cycles help to align our internal physiological functions with the external environment. Man is a diurnal specie sleeping during night and active during daytime. Therefore, abrupt disruptions from the normal functioning of work and sleep cause disorders. In quest of making the best of our schedule while maintaining good health, understanding sleep is important. Shift work should happen in the optimal phase where alertness and performance are at their peak. In a healthy worker all circadian rhythms are in tune, they change as one ages and so does your ability to respond to time cues. Timing is important for instance, body temperature will rise before waking up. It happens to promote a feeling of being fresh and alert. A drop in temperature occurring in the afternoon between 2-4 pm makes people fall asleep commonly known as a nap this is not a good time to work.

A suitable approach to night shift scheduling is to avoid rotating shifts. If possible an organization with people working night shift is encouraged to retain them. When need to change comes it is recommended to work 4-6 weeks consecutively to allow circadian system adjust slowly for performance and health. The other issue is the length of the shift. In most instances this is majorly determined by social pressures from financial strains in running a family where parents or victims tend to overdo it for payment. 7 to 8 hours is a span that ensures that a relaxed remains active and productive without readaptation issues due to extra hours. Rather than straining to remain awake which with time takes its toll by chronic illnesses it is better to have enough rest without switching shifts too soon (Knutsson, 2003)

Another way to help with shift work especially with emergency shift is to use a split sleep period a method that allows one to sleep for 3-4 hours prior to going to work and another 3-4 hours soon after a night shift. Unplanned naps can be problematic since they hinder adaptation but when scheduled regularly they are effective in night shifts. Worth noting, sedatives are unhealthy when used routinely by night shift workers this is because they do not speed up adaptations though they may increase total sleep time during the day. Also, caffeine should be avoided within duration of 3-4 hours of a scheduled sleep time.

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