Biopsychology: Circadian Rhythms Flashcards
1
Q
What Are Biological Rhythms?
A
- Cyclical changes in the way our biological systems behave.
- They have evolved because of the environment.
- They are governed by endogenous pacemakers and exogenous zeitgebers.
2
Q
What Are Endogenous Pacemakers?
A
- Internal body clocks that regulate many biological rhythms.
3
Q
What Are Exogenous Zeitgebers?
A
- External cues that may affect or entrain our biological rhythms.
4
Q
What Are Circadian Rhythms?
A
- Any cycle which lasts about 24 hours.
- Optimise an organism’s bodily functions and behaviour to best meet the varying demands of the day and night cycle.
- The rhythm is regulated by an internal system e.g release of hormones.
- Examples of circadian rhythms are sleep-wake cycle, body temperature, hormone production.
5
Q
Sleep-Wake Cycle.
A
- Light and dark provide signals about when we should be awake and when we should be asleep.
- The sleep wake cycle dips and rises at different times.
- Our strongest sleep drive occurs between 2-4am and 1-3pm.
- Sleepiness is less intense with circadian dips if we have had sleep the night before.
- Homeostasis controls our need to sleep, if we need more energy our body tells us to sleep which is why we get tired the longer we are awake.
- The effect of daylight (exogenous zeitgeber) has an important effect on when we feel drowsy and awake.
6
Q
Sleep-Wake Cycle Research: Siffre Description.
A
- Spent extended periods of time underground to study the effect on his circadian rhythm. He was deprived of natural light.
- Found that the absence of external cues significantly altered his circadian rhythm.
- He believed the date to be a month earlier than it was.
- This suggests that his 24 hour sleep cycle was increased by the lack if external cues, making him believe that one day was longer than it was, leading him to think that fewer days had passed.
7
Q
Sleep-Wake Cycle Research: Siffre Evaluation Points.
A
- Not generalisable or representative as individual differences may occur.
- They had artificial light which defeated the purpose as they are no longer measuring the aim therefore reducing validity.
- High reliability - can be repeated.
- Applicable.
8
Q
Sleep-Wake Cycle Research: Aschoff Wever Description.
A
- Group of participants spent 4 week in a WWII bunker deprived of natural light.
- All but one of the participants displayed a circadian rhythm of between 24-25 hours (anomaly of 29 hours).
- Natural sleep-wake cycle may be longer than 24 hours but external cues keep us to that time.
9
Q
Sleep-Wake Cycle Research: Aschoff Wever Evaluation Points.
A
- May have tampered/damaged the participants sleep cycle.
- Not generalisable as there are individual differences shown in the anomaly.
- They had artificial light which means they aren’t measuring the aim of the study therefore reduce validity.
- High reliability.
- Applicability.
10
Q
Sleep-Wake Cycle Research: Folkard Description.
A
- 12 people lived in a dark cave more 3 weeks.
- Went to bed when the clock said 11:45pm and woke when it said 7:45am.
- Researchers sped up the clock so a ‘24 hour day’ lasted 22 hours.
- None of the participants were able to comfortably adjust to the shorter day.
- Suggests the existence of a strong free-running circadian rhythm cannot be easily ridden by environmental changes.
11
Q
Sleep-Wake Cycle Research: Folkard Evaluation Points.
A
- May have tampered/damaged sleep cycle.
- Not generalisable as individual differences may affect results.
- They had artificial light so they are not measuring their aim therefore reduces validity.
- High reliability as there are other supporting studies.
- Applicability.
12
Q
Hormone Production And Circadian Rhythms.
A
- Hormone production follows a circadian rhythm.
- Melatonin is produced and released from pineal gland.
- Melatonin peak during the hours of darkness.
- By activating synapses in the brain, melatonin encourages the feelings of sleep.
- When it is dark, more melatonin is produced and when it is light less melatonin is produced.
13
Q
Body Temperature And Circadian Rhythms.
A
- Body temperature is at the lowest about 4 am and highest at 6pm, varying around two degrees from 36C in the morning and 38C in the evening.
- Sleep occurs when the body temperature drops.
- Temperature rises during the last 2 hours of sleep causing people to feel alert in the morning.
- Small drops in temp happen between 2-4pm which can account for why people feel sleepy during this time.
14
Q
Body Temperature And Circadian Rhythm Examples.
A
- There is evidence to suggest that body temp may have an effect on our mental abilities the warmer we are (internally) the better our cognitive performance.
- Folkard et al found that children who had stories read to them at 3pm showed superior recall and comprehension after a week compared to children who heard the same stories at 9am.
- Gupta found improved performance on IQ tests when participants were assessed at 7pm as opposed to 2pm and 9am.
15
Q
Circadian Rhythm Evaluation: Strength - Practical Application Shift Work.
A
- Circadian rhythm has practical application to shift work.
- Boivon et al found shift workers experience a lapse of concentration around 6 am (a circadian trough) so mistakes and accidents are more likely.
- This may have economic implications in terms of how best to manage worker productivity and safety.
- Shift changeovers could occur before a circadian trough to reduce mistakes, meaning work would not have to be redone and reduce accidents so people can continue to work contribute to the economy.
