Environmental topic 2 - biological rhythms

Question 1

Background - Part 1

Answer 1

Biological rhythms - distinct patterns of change in the body activity that conform to cyclical periods
- circadian rhythms - sleep-wake cycle
- cycles influenced by endogenous pacemakers or internal body clock
- biological rhythms influenced by external - exogenous zeitgebers - light or temperature
- Suprachiasmatic nucleus - acts as internal body clock and sends signals around body on 24 hour schedule

Question 2

Background - Part 2

Answer 2

• as the biological clock isn’t 24 hours, exogenous zeitgeber needed to ‘reset’- pineal glands help this:
• they produce and release melatonin and internal body clock with the external world - more is produced when dark
  Summary of the human sleep cycle:
  1. light enters the eyes - neurons convert protons to electrical signals in the retina
  2. retinal neurons send signals to the optic nerve
  3. level of light reaches suprachiasmatic nucleus
  4. The pineal gland secretes melatonin around body

Question 3

Background - Rechtstaffen and Bergman

Answer 3

• ‘dish over water method’ - rat would be placed on a spinning dish, if brain monitors suggested they were falling asleep, they would have to move to not fall in water
• standardised - temperature and food and drink, deprivation of sleep
• rats died after a couples of weeks compared to control rates that didn’t
• they had increased food intake and lost body heat

Question 4

Background - Michel Siffe

Answer 4

• found that once isolated in cave, experienced 25 hour days and had same cycle as on surface
• thought it was a few months earlier than it was and suffered from memory impairment in the cave
• in cave took regular blood pressure, heart rate and brain activity measurements - throughout 7 month case study

Question 5

Background - Recht

Answer 5

• travelling across time zones and the impact on basketball performance - studying the last three seasons
• travel east to west (phase delay) - 43.8% of away games won
• travel west to east (phase advance) - 37.1% of away games

Question 6

Background - Tilley

Answer 6

• 12 shift workers on quality and performance at work - shifts changed often on three-week study
• when working nights, sleep was shorter and disrupted
• work reaction and decision-making were impaired as the number of night shifts increased
• shift workers slept on average 1-2 hours less than individuals with normal day jobs

Question 7

Key research - Czeisler - aim and sample

Answer 7

aim: experiences of workers on rotating shift patterns - redesigning a company shift patterns
sample: 153 male employees at potash plant in Utah - aged 19 - 68
- 85 worked phase advancing - ‘anti-clockwise’ rotation
- 68 used as control of not shift

Question 8

Key research - Czeisler - procedure

Answer 8

Stage 1:
- before shifts are allocated, all 153pts - self-report done about health, shift work preference and sleep-wake cycle
- those with rotating shifts more likely to have insomnia problems compared to control
Stage 2:
- given suggestions on adjusting sleep time to the new schedule
- the new shift was phase delay - so the circadian rhythm could be easily adjusted
- 33 rotated every 7 days, 52 rotated shifts every 21 days
- then assessed three months later with a questionnaire and productivity and turnover after nine months

Question 9

Key research - Czeisler - results and conclusions

Answer 9

Results:
- preferred phase delay over advancing
- 21-day rotation, complained less from 90% to 20% - rated themselves as healthier
- staff turnover on 21 days was reduced to the same range of control
- increase in rates of both Potash harvesting and production after the 21-day schedule
conclusions:
- beneficial to circadian rhythms, when designing shift work, improves job satisfaction, minimises impact on workers, decrease personal turnover, increase productivity

Question 10

Key research - Czeisler - evaluation

Answer 10

Strengths:
- large sample - generalisability high
- quantitative and qualitative data
- field experiment - high ecological validity, mundane realism and applied to other manufacturing
Weaknesses:
- androcentric and ethnocentric sample
- self - reports - social desirability
- lack control - individual variables and external stressors
- lack of females but representative to the manufacturing environment
Debates:
- Free will vs determinism

Question 11

Application - Fallis and schedule change strategies

Answer 11

Fallis - found that when nurses in Canada took naps during shifts, they had improved energy and mood
- however, crowded and small areas, brightness and lack of organisation could limit the schedule
Schedule change strategies:
- night shift - given more money or premium
- an enhanced sense of comradeship, fewer distractions and disruption
- opportunities to build skillsets and arrange work times
- create a healthy work/life balance
- improve mental wellbeing, less absenteeism

Question 12

Application - Wiseman

Answer 12

combatting jet lag:
1. start to shift your body clock before going anywhere
2. adjust watch as soon as on a plane
3. if need to sleep avoid sitting on the sunnyside
4. know whether to seek out or avoid light when reaching destination
5. melatonin supplements to control sleeping patterns
6. if trip short may not need to adjust at all