Biological Rhythms (biological) Flashcards
Biological rhythms
They are governed by both the bodies internal biological ‘clocks’, which are called endogenous pacemakers + external cues from the environment known as exogenous zeitgebers (time giver).
- endogenous pacemakers = the main body clock = suprachiasmatic nucleus (SCN). The SCN receives info about light levels form the optic chiasm. When light levels low SCN instructs pineal gland to release melatonin, this chemical induces sleep.
- exogenous zeitgebers = external ques that fine tune the SCN and other body clocks e.g. daylight which signals waking up
Different types of biological rhythms
- ultradian rhythms = occur many times during the day, such as the cycles of sleep. Adults = 5-6 cycles per night - each cycle involves going through 5 stages of sleep (including deep + light sleep)
- circadian rhythms = around 24 hours. Such as the sleep-wake cycle + body temp
- infradian rhythms = longer than a day to complete such as menstrual or breeding cycle.
- circannual rhythms = happen on annual basis, e.g. migration of birds or seasonal affective disorder (depression only in winter)
A circadian rhythm : the sleep-wake cycle + Siffre’s (1975) cave study
sleep wake cycle = regulated by exogenous zeitgebers or endogenous. a free running biological rhythm occurs if the biological clock is left to own devices
Siffre’s cave study = his free running clock more or less stayed the same when he lived in a cave for 2 months, suggesting that circadian rhythms must be biological. internal cues must have governed his biological rhythms as there was no exogenous zeitgebers.
jet travel
jet lag occurs because exogenous zeitgebers do not match our endogenous pacemakers.
The process of holding back sleep is called phase delay. However going to a place which is 5 hours later is known as phase advance and is much harder to cope with. It is harder to cope with as it is shortening the natural 24 hour cycle.
the effects of jet travel
Jet lag can lead to various negative cognitive and + physiological effects such as loss of concentration, increased anxiety, depression + mood swings (green 2011)
Lawrence Recht + colleagues (1995) found decreases in physical ability + skill when baseball players suffered form jet lag. Showed USA won 44% of games when travelling from east coast to west coast to play a game (3 hour time difference). However only won 37% of games when travelling form west coast to east coast. Can be explained in terms of the disruption of the biological rhythms.
shift work
Shift work is used for many different reasons - social, technological + economic reasons. Shift work provides society with 24 hour a day services however requires staff to work against their natural circadian rhythms. Diane Boivin eat al (1997) refers to circadian trough, occurs between midnight, where cortisol levels are lowest + 4am when body temp is lowest. Consequent being decrease alertness.
the effects of shift work
- Andrew Tilley et al (1982) studied performance and sleep quality in 12 male shift workers whose shift patterns frequently changed during course of 3 week study. When working nights researchers found that although workers slept during the day it was often short and more disrupted.
- Therefore causing reaction times + decision-making abilities impaired as the number of nights shifts increased.
- illustrates problems in performance due to lack of sleep that shift work can cause.
background of Czeisler (1982)
26.8% of Americans work shifts, rotating between night, evening, and daytime.
25 hour circadian Rhythm
24 hour clock
Shift work violates the circadian Rhythm.
aim
Czeisler et al.’s aim was to demonstrate that when schedules that consider properties of the human circadian system are introduced there will be a positive effect on:
- Work schedule satisfaction.
- Health (less time off)
- Staff turnover (fewer staff leaving)
- Worker productivity.
sample ( the great salt lake minerals + chemical corporation in Ogden, Utah)
September-May Potash season, 8 hour shifts for 7 days, Phase advance work schedules;
1. Midnight-8am night shift
2. 4pm-Midnight swing shift
3. 8am-4pm- Day shift
sample
153 male employees
85 rotating shift to phase delay - split into 2;
> 33 changed shift every 7 days
> 52 changed shift every 21 days
68 control group- no rotation in shifts- only day or swing shifts
IV- shift type
DV - measures of job satisfaction, health indices, personnel turnover and productivity.
Czeisler procedure
- All workers + managers attended a audio-visual presentation on basic properties of circadian sleep-wake cycle that had suggestions for adjusting their sleep time to their schedule
- Each received an educational booklet designed for the workers at this facility
- Questionnaires given out to measure workers’ satisfaction, health, personnel turnover, + productivity. measured before and after introduction of new shift work schedules. As the researchers manipulated the shift work schedules of workers (IV), this study was also a field experiment.
- The workers’ preferences were evaluated from other questionnaires distributed three months after the introduction of the new schedules
- Personnel turnover and plant productivity were analysed nine months after the introduction of the new schedules.
results before the study
The rotators reported significantly more problems with insomnia non-rotators.
29% of the rotators reported that they had fallen asleep at work at least once during the previous three months.
A major complaint was that the schedule changed too often.
81% reported that it took two to four days or more for their sleep schedule to adjust after each phase advance; this included 26% who said they were never able to adjust before being rotated again.
results after the introduction to the new shift schedules
The workers clearly preferred the phase delay
direction of rotation.
Complaints that the schedule changed too often
dropped from 90% to 20% among the workers
on the 21-day phase delay rotation schedule.
