Biopsychology - Biological rhythms

Question 1

What are biological rhythms?

Answer 1

• distinct patterns of changes in body activity that follow cyclical periods

Question 2

What are circadian rhythms?

Answer 2

• biological rhythm that lasts around 24 hours and takes place once in 24 hours
• driven by suprachiasmatic nuclei (SCN) in hypothalamus
  
  • pacemaker must constantly be reset to ensure body is in sync with outside world
  • photoentrainment = setting body clock to correct time with the help of light

Question 3

What is the sleep-wake cycle?

Answer 3

• strongest sleep drive = between 2:00 - 4:00 and 13:00 - 15:00
• under homeostatic control, this drive increases throughout the day until it is late in the evening
  
  • daylight = circadian system keeps us awake
• free-running cycle

Question 4

What is Michel Siffre’s study?

Answer 4

• spent long periods of time living underground with no external cues
  
  • ate, slept, woke up when he felt like it
  • internal clock was his only influence
• he lost track of time while underground
• he then spent 6 months in a cave and his natural circadian rhythm had settled down to just over 24 hours

Question 5

What is core body temp. for circadian rhythm?

Answer 5

• lowest = 36 degrees C at around 4:30
• highest = 38 degrees C at around 6:00
• sleep occurs when the body temp. lowers and rise of body temp. occurs at the end of sleep
  
  • Folkard (1977) children who had stories read to at 3pm showed superior recall and comprehension after a week compared to at 9am
  • Gupta (1991) those assessed at 7pm had improved IQ performance compared to those assessed at 2-4pm

Question 6

What is hormone production in circadian rhythm?

Answer 6

• release of melatonin from pineal gland peaks during hours of darkness
• activation of chemical receptors in the brain encourages sleep
  
  • light drops the production of melatonin
  • since it is produced once in 24 hours, it is a circadian rhythm

Question 7

What are the strengths of circadian rhythms?

Answer 7

• chronotherapeutics (study of how timing affects drug treatment)
  
  • important that right conc. of medication is given to the right area of the body at the right time
• better understanding of adverse consequences of disruption of circadian rhythms
  
  • Knutsson (2003) found that shift workers are three times likely to develop heart disease
  • those on night shift have a reduced period of conc. at 6:00

Question 8

What are the weaknesses of circadian rhythms?

Answer 8

• small sample sizes/case studies
  
  • questions generalisability of the studies as they may not be truly representative of the target population as a whole
    - e.g. Siffre found that his internal clock ticked much slowly than when he was younger (factors like age can prevent general conclusions)
• flaw in methodology
  
  • ppts were deprived of clocks and daylight but not artificial lights like a torch
  • so they were still exposed to exogenous cues
  • Czeisler (1999) altered ppts’ circadian rhythms by manipulating the use of artificial lighting alone

Question 9

What are ultradian rhythms? (sleep cycle)

Answer 9

• biological rhythm that lasts less than 24 hours and takes place more than once in 24 hours
• sleep cycle is an example of an ultradian rhythm
  
  • alternates between REM (rapid eye movement) and NREM
  • 5 stages = light sleep, deep sleep, REM sleep (brain waves speed up, dreaming occurs)
  • repeats every 90 minutes
• NREM stages:
  
  • 1/2 = light sleep, from alpha to theta waves (get slower)
  • 3/4 = deep sleep, delta waves (slow)
• stage 5 = REM, body is paralysed and brain activity resembles an awake person (theta waves)

Question 10

What is Dement and Kleitman’s (1957) study?

Answer 10

• 7 adult males and 2 adult females (no caffeine) were asked to report to lab at bedtime
  
  • connected to EEG for 61 nights
  • measurements were taken while sleeping
  • woken up at different stages and asked if they had been dreaming
• found that they all had periods of REM
  
  • many recalled their dream when awakened during REM
  • brain activity was different in vivid dreams compared to less clear dreams
• stages of sleep follow particular pattern and dreams occur in REM

Question 11

What are the strengths of ultradian rhythms?

Answer 11

• research support
  
  • Dement and Kleitman’s study supported idea that ultradian rhythms do occur (e.g. sleep)
• Basic Rest Activity Cycle (takes place when we are awake)
  
  • Ericsson (2006) studied group of violinists and found that each practise session was 90 mins long
  • violinists frequently napped to recover
  • this was found among other musicians, athletes, chess players
  • ** 90 mins of practice allows for max performance **

Question 12

What are the weaknesses of ultradian rhythms?

Answer 12

• individual differences
  
  • Tucker (2007) suggested that there are differences in sleep patterns which may be genetics
  • ppts were studied over 11 days/nights and found that there were differences in all of the characteristics
  • hard to generalise results from other studies

Question 13

What are infradian rhythms (menstrual cycle)?

Answer 13

• biological rhythm that lasts longer than 24 hours, can last weeks, months or a year
• female menstrual cycle promotes ovulation or stimulates uterus for fertilisation
  
  • ovulation = halfway through cycle (high oestrogen) and lasts 16-32 hours
  • progesterone levels then rise after ovulation
  • usual cycle is around 28 days
• ** endogenous system but may be influenced by exogenous factors **

Question 14

What are strengths of menstrual cycle?

Answer 14

• research support influence of exogenous zeitgebers (external factors)
  
  • Reinberg (1967) examined menstrual cycle of woman with only a small lamp
  • found that her cycle had shortened to 25.7 days (lack of light affected her cycle)
  • Russel (1980) found that cycles become synchronised with other women through odour exposure
  • sweat from one group of women was rubbed onto upper lip of another group and they found that their cycles were in sync despite being separated
• psychologists claim that synchronised cycles provided an evolutionary advantage
  
  • multiple pregnancies at once means that childcare can be shared amongst many mothers
• important regulators of behaviour
  
  • Penton-Volk (1999) found that women preferred feminine faces at least fertile stage of cycle and more masculine faces when most fertile
  • indicates that women’s sexual behaviour is motivated by their infradian rhythms

Question 15

What are weaknesses of menstrual cycle?

Answer 15

• methodological limitations
  
  • many factors can affect menstrual cycle like stress, diet, exercise (confounding variables)
  • due to this, other studies have failed to replicate the findings of the synchronised cycles
• ignores other factors
  
  • only focuses on the influence of exogenous zeitgebers such as pheromones and not endogenous pacemakers
  • this makes it environmentally determinist

Question 16

What are infradian rhythms (SAD)?

Answer 16

• seasonal affective disorder is an infradian cycle governed by yearly cycle
  
  • melatonin (pineal gland) is partly responsible as the lack of light during winter months results in a longer period of melatonin secretion (linked to depressive symptoms)

Question 17

What are the strengths/weaknesses of SAD?

Answer 17

• research support for role of melatonin (+)
  
  • Terman (1988) found that rate of SAD is more common in Northern countries where winter nights are longer
  • suggests that SAD is affected by light (exogenous zeitgeber)
• practical applications (+)
  
  • effective treatments for SAD include phototherapy (light box that stimulates very strong light in morning/evening)
  • this helps to reset melatonin levels, which then regulates serotonin levels and improves symptoms i around 60% of sufferers
• placebo effect (-)
  
  • 30% of ppts showed improvement when treated with placebo

Question 18

What are endogenous pacemakers?

Answer 18

• internal body clock that centres in the brain and plays the main role in controlling biological rhythms
• e.g. SCN, which is a cluster of nerves in the hypothalamus
  
  • helps generate circadian rhythms as neurons within the SCN synchronise with each other (receive coordinated signals)
  • also secretes melatonin in the pineal gland by sending a signal to increase its production at night

Question 19

What are strengths of endogenous pacemakers?

Answer 19

• research support
  
  • Morgan (1995) bred hamster with a circadian rhythm of 20 hours and its SCN neurons were transferred to other hamsters
  • they then display circ. rhythms of around 20 hours
  • the SCN of normal hamsters were transplanted into abnormal hamsters and their circ. rhythms changed to 24 hours
• DeCoursey (2000) destroyed SCN connections to the brains of 30 chipmunks
  
  • sleep/wake cycle disappeared and significant proportion of them were killed as they were awake when they should have been asleep

Question 20

What are weaknesses of endogenous pacemakers?

Answer 20

• unethical
  
  • animal studies conducted are unethical
  • they are also not ecologically valid as people do not have their circadian rhythms deliberately tampered with
• exogenous zeitgebers
  
  • Folkard (1996) found that Kate’s sleep cycle had extended to 30 hours with 16 hours of sleep recorded
  • suggests that exogenous zeitgebers like light and social cues may have a greater effect than endogenous pacemakers

Question 21

What are exogenous zeitgebers?

Answer 21

• environmental factors that help synchronise biological rhythms with the outside world (e.g. light)
• light
  
  • receptors in SCN are sensitive to changes in light levels
  • melanopsin = protein in retina
  • moving to country with diff. time zone leads to disrupted sleep patterns as endogenous pacemakers impose their inbuilt system of sleep which is not in synch with exogenous zeitgebers
• social cues
  
  • Aschoff (1971) showed that individuals are able to compensate for the absence of natural light by responding to social cues
  • circ. rhythm of blind people were the same as sighted people as they were exposed to the same social cues

Question 22

What are strengths of exogenous zeitgebers?

Answer 22

• research support on the role of melanopsin
  
  • Skene and Arendt (2007) estimate that most blind subjects who have some light perception have normal circ. rhythms
  • shows how exogenous zeitgebers are still important in the sleep wake cycle
• Burgess (2003) found that light exposure could be used to avoid jet lag (important application)

Question 23

What are weaknesses of exogenous zeitgebers?

Answer 23

• not all studies support the influence of light on sleep wake cycle
  
  • Vetter (2011) compared sleep wake cycle/activity rest of 2 groups of ppts
  • those under warm light synchronised their rhythms with the natural light of dawn, blue light ppts synchronised to office hours
  • shows how important the shade of light is as well as whether it is natural/artificial
• ** natural light is more influential than artificial **