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Psychology - CS - Biopsychology > 5 - Biological Rhythms > Flashcards

5 - Biological Rhythms Flashcards

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1
Q

Define biological rhythms

A

Distinct patterns of changes in body activity (controlled by internal + external factors) that conform to cyclical time periods

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2
Q

What two things are all biological rhythms regulated by?

A
  • Endogenous pacemakers

- Exogenous zeitgebers

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3
Q

What are endogenous pacemakers?

A
  • Internal factors
  • Work as an internal body clock to regulate biological rhythms
  • E.g. suprachiasmatic nucleus (involved in sleep-wake cycle)
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4
Q

What are exogenous zeitgebers?

A
  • External factors
  • Changes in the environment that influence our body clock + rhythms
  • E.g. light + social cues (involved in sleep-wake cycle)
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5
Q

What are the three types of biological rhythms?

A
  • Circadian rhythms
  • Infradian rhythms
  • Ultradian rhythms
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6
Q

Define circadian rhythms

A

Biological rhythms that occurs in cycles once every 24hrs

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7
Q

What is the example of circadian rhythms we use?

A

Sleep-wake cycle

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8
Q

What is the sleep-wake cycle?

A

A circadian rhythm (usually 8 hrs sleep every 24hrs)

Causes us to feel awake/alert in the day and drowsy at night

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9
Q

What exogenous zeitgebers influence the sleep-wake cycle?

A
  • Light

- Social cues

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10
Q

What endogenous pacemakers influence the sleep-wake cycle?

A

Suprachiasmatic nucleus (SCN)

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11
Q

What is the Suprachiasmatic nucleus (SCN)?

A
  • Endogenous pacemaker involved in the sleep-wake cycle

- Bundle of nerves in the hypothalamus working a an internal body clock

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12
Q

Outline how the SCN works in the sleep-wake cycle?

A
  • Nerve fibres in the eye cross in the optic chiasm
  • SCN sits just above the optic chiasm
  • SCN detects light in the optic chiasm as its being sent to visual cortex
  • SCN sends info to pineal gland about whether its light or dark
  • If dark: pineal gland produces melatonin (inducing sleep)
  • If light: pineal gland is prohibited from producing melatonin (preventing sleep)
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13
Q

What are two pieces of research on the sleep-wake cycle (circadian rhythm)?

A
  • Siffre (cave study)

- Folkard et al (cave study, changing clock)

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14
Q

Outline Siffre’s cave study 1962 (aim, process, findings, conclusion)

A

Aim: to see if we have endogenous pacemakers causing our sleep-wake cycle
Process: spent 2 months isolated in a cave - no sunlight or clock
Findings: body chose when to eat and sleep, settled into a sleep-wake cycle of 25-30hrs
Conclusion:
- Supports existence of endogenous pacemakers: settled into a regular cycle of approx 25hr day
- Supports existence of exogenous zeitgebers: cycle wasn’t ‘norm’ of 24hrs

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15
Q

Outline Folkard’s cave study 1985 (aim, process, findings, conclusion)

A

Aim: to see if our internal body clock can be overridden by exogenous zeitgebers
Process: 12 ppts spent 3 weeks in dark cave. Told to go to bed when clock said 11:25pm + wake up at 7:45am. Changed clock to 22hr day.
Findings: Only 1 ppt could comfortably adjust to new regime
Conclusion:
Our internal body clock is very strong + it is very hard to override using exogenous zeitgebers

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16
Q

What is the natural length of humans’ sleep-wake cycle?

A

Slightly over 24hrs

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17
Q

What is the sleep-wake cycle length for humans? Why?

A

24hrs

  • Naturally slightly longer
  • Entrained by exogenous zeitgebers
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18
Q

What happens if the sleep-wake cycle is disrupted?

A
  • Poor health
  • Low concentration
  • High anxiety
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19
Q

Give 2 positive evaluation points for circadian rhythms

A

Real world application (shift work)
- Understanding circadian rhythms can help improve conditions for shift workers
- Night shifts can disrupt sleep-wake cycle pattern + cause…
Circadian troughs (reduced conc - usually at 6am)
Poor health (3x more likely to get heart disease)
- Have concluded we should reduce shift work + give readjustment periods
- So, research has helped improve health + conc (+ productivity)

Real world application (medical treatment)

  • Understanding circadian rhythms has contributed to chronotherapeutics
  • If medicine is given at specific times (corresponding to rhythms) treatment will be more effective
  • E.g. rhythms make heart attacks most common in early morning, novel medicine given at 10pm to release early morning, reduced heart attacks
  • Understanding bodily rhythms over the day (circadian) improved treatment
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20
Q

Give 2 negative evaluation points for circadian rhythms

A

Methodological issues with Siffre + Folkard

  • Small samples, affected by individual differences
  • Sleep-wake cycles may vary by 13hrs-65hrs
  • Time when asleep/awake also varies (Duffy’s larks + owls)
  • Hard to make generalisable conclusions about circadian rhythms when individual differences are so significant

Reductionist

  • Trying to isolate role of endogenous pacemakers + exogenous zeitgebers (e.g. in Siffre’s study on circadian rhythms) is biologically reductionist
  • Trying to reduce the cause of rhythms has low ecological validity, as in real life the two causes will never be separated
  • So, would be more useful in real world to use an interactionist model, rather than trying to separate the role of internal + external factors
21
Q

What does it mean to be a ‘lark’?

A

Wake up early + sleep early

22
Q

What does it mean to be an ‘owl’?

A

Wake up late + go to sleep late

23
Q

Give 2 positive evaluation points for endogenous pacemakers + exogenous zeitgebers

A

Siffre

  • Supports endogenous: settled into rhythm
  • Supports exogenous: rhythm longer than norm (25hrs)
  • Both important

Real world application (Shift work)

  • Understanding importance of endogenous pacemakers + the issues that come with disrupting the natural sleep-wake cycle has led to improvements in shift work
  • Reduced shift work + longer adjustment periods
  • Has improved health + concentration of workers
24
Q

Give 2 negative evaluation points for endogenous pacemakers + exogenous zeitgebers

A

Reductionist

  • Research has tried to isolate two causes (unrealistic + reductionist)
  • Need to use interactionist model for conclusions that apply to real world

Research has suggested endogenous pacemakers are still superior
- Limitation of exogenous zeitgebers
- E.g. Miles
Did case study of young blind man (unaffected by light + social cues)
Found strong sleep-wake cycle of 25hrs
- So, endogenous pacemakers are important in keeping biological rhythms + are only slightly entrained (approx 1 hr) by exogenous zeitgebers

25
Q

What is the piece of research supporting endogenous pacemakers?

A

DeCoursey
- 30 chipmunks
- Looked at endogenous pacemaker SCN
- Destroyed their SCN + let them back into wild to observe for 80 days
- Findings: Sleep-wake cycle disappeared by end of study
Significant proportion killed by predators (because they were awake at unsafe times + hunted)
- Conclusion: SCN is a very important endogenous pacemaker + the sleep-wake cycle cannot exist in the same way without it

26
Q

What is the piece of research supporting exogenous zeitgebers?

A

Campbell + Murphy
- Looked at exogenous zeitgeber light
- 15 ppts
- Woke them during sleep + shone torch on back of knees
- Findings: this light could alter sleep-wake cycle by up to 3hrs
- Conclusion: light is an important exogenous zeitgeber as it impacts the natural sleep-wake cycle
(Also - may be other light receptors not just the SCN)

27
Q

Define infradian rhythms

A

Biological rhythms that occur less than once every 24hrs

28
Q

What example of infradian rhythms do we use?

A

Female menstrual cycle

29
Q

What is the female menstrual cycle?

A

An infradian rhythm which occurs over an average of 28days (between the first day of womb shedding/period to the day before the next period) due to changes in hormones over a month

30
Q

What endogenous pacemakers influence the female menstrual cycle?

A

Hormones

  • Oestrogen levels rise (ovary develops egg then ovulates)
  • Progesterone levels rise after ovulation (womb lining thickens)
  • If pregnancy doesn’t occur egg is absorbed + lining breaks down in menstrual flow
31
Q

What exogenous zeitgebers influence the female menstrual cycle?

A
  • Women synchronising
  • Diet/health
  • Stress
  • Contraceptive pill
32
Q

Give 2 positive evaluation points for infradian rhythms

A

Research support

  • Stern + McClintock support that infradian rhythms are governed by an endogenous system, affected by exogenous factors
  • They focused on the menstrual cycle + affect of women
  • 29 female ppts with irregular periods
  • Pheromones gathered from 9 women (pad under armpit for 8 hrs) + given to other 20 women (rubbed on upper lip)
  • Findings: 68% ppts experienced cycle changes to match ‘odour donor’
  • Supports affect of endogenous + exogenous influence on rhythms

Evolutionary advantage of infradian rhythms

  • Menstrual cycle (infradian rhythm) can synchronise with other women to get an evolutionary advantage
  • In the past, allowed mothers to give birth at same time, so if mothers die in childbirth the orphan can get milk from the social group
  • Today, giving birth at same time means help with shared childcare
  • Synchronisation may be a valuable theory, showing how infradian rhythms can provide evolutionary benefits
33
Q

Give 2 negative evaluation points for infradian rhythms

A

Methodological issues with research

  • Research into infradian rhythms (Stern + McClintock) has flaws
  • Small sample (29): hard to generalise findings
  • Self report (about cycle changes): may lie due to demand c
  • Confounding v (stress, diet, etc): may cause change, lowering internal v
  • So, supporting research about infradian rhythms may be weak, with flawed conclusions

Issues for the legal system

  • PMS (linked to infradian rhythm of menstrual cycle) used as legal defence
  • Dalton argued severe PMS is like a mental disorder + individuals cant be held accountable (biological determinism)
  • E.g. Ms English - killed married lover, had PMS, manslaughter charge
  • Infradian rhythms are seen as biologically deterministic due to the strong role of endogenous pacemakers, causing legal issues
34
Q

Define ultradian rhythms

A

Biological rhythms that occur more than once every 24hrs

35
Q

What is the example of ultradian rhythms we use?

A

The sleep cycle (stages of sleep)

36
Q

What is the sleep cycle?

A

An ultradian rhythm. A continuous 90 min cycle of sleep that repeats during sleep, with each cycle broken into 5 stages.

37
Q

How long is one sleep cycle?

A

90 mins

38
Q

How many sleep cycles does the average person go through each night?

A

5

39
Q

How have we gained our understanding of sleep cycles and the stages of sleep?

A

EEG recordings

40
Q

What is Stage 1 of the sleep cycle?

A

Light sleep where person may be easily woken

  • Alpha waves (high frequency, low altitude)
  • NREM
41
Q

What is Stage 2 of the sleep cycle?

A

Light sleep where person may be easily woken

  • Alpha waves (high frequency, low altitude)
  • Some ‘sleep spindles’ (random wave changes - thought to inhibit cognitive functions to allow for sleep)
  • NREM
42
Q

What is Stage 3 of the sleep cycle?

A

Deep sleep/slow wave sleep (SWS) where a person is hard to wake

  • Delta waves (low frequency, high amplitude)
  • NREM
43
Q

What is Stage 4 of the sleep cycle?

A

Deep sleep/slow wave sleep (SWS) where a person is hard to wake

  • Delta waves (low frequency, high amplitude)
  • NREM
44
Q

Which stages of the sleep wake cycle are the same or very similar to each other?

A
  • Stage 1 + 2 (very similar - difference is sleep spindles in 2)
  • Stage 3 + 4 (same)
45
Q

What is Stage 5 of the sleep cycle?

A

Body is paralysed yet brain is active, resembling an awake brain

  • Theta waves
  • Eyes move under lids
  • REM
46
Q

What is REM?

A

Rapid Eye Movement

  • Associated with dreaming
  • In Stage 5 of the sleep cycle
47
Q

What is NREM?

A

Non-Rapid Eye Movement

  • Not associated with dreaming
  • In Stage 1,2,3,4 of the sleep cycle
48
Q

Give 2 positive evaluation points for ultradian rhythms

A

Research support

  • Dement + Kleitman
  • Aim: to measure variations in sleep stages (an ultradian rhythm)
  • 9 ppts
  • Lab where EEGs recorded during sleep
  • Controlled some confounding variables: alcohol, caffeine
  • Findings: identified changes in brainwaves that matched 5 stages of sleep + found correlation between REM waves and reports of dreaming
  • Research supports the existence of 5 sleep stages + that sleep is an ultradian rhythm because it was recorded multiple times per night

Sleep deprivation
- Problems associated with sleep deprivation support importance of ultradian rhythms such as the sleep cycle
- E.g Randy Gardener
Awake for 264hrs
Findings:
Blurred vision, disorganised speech, hallucinations
After, he slept for 15hrs
Sleep recovery = 70% Stage 4, 50% Stage 5, little of other stages
- Problems after not sleeping support importance of this rhythm
- Different rates of recovery suggest some stages are even more important for our survival than other (i.e. Stage 4 + REM)

49
Q

Give 2 negative evaluation points for ultradian rhythms

A

Methodological issues

  • Issues with supporting research methodology (Dement + Kleitman)
  • Small sample (9): hard to generalise
  • EEGs: Have to make inferences that change in brainwaves means change in stage of sleep (this isn’t a certainty)
  • Lab: Lacks ecological validity - may not represent natural sleep pattern
  • Flaws in research supporting infradian rhythm of sleep stages may have led to flawed conclusions about these rhythms, low in validity

Individual differences

  • The significant variations between people limits ultradian rhythms
  • E.g. Tucker et al - found significant differences between peoples’ duration of each stage (particularly 3 + 4). Suggested these were biologically determined
  • E.g. Kale + Kale - found differences in each. Older people sleep less (approx 6 hrs)
  • So, it is difficult to make a valid theory about ‘normal sleep’ because ultradian rhythms can change between individuals + over time

Psychology - CS - Biopsychology (5 decks)

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