Biopsychology-Biological rhythms- TB Flashcards
What are biological rhythms?
Patterns of change in body activity that conforms to a cyclical period
What is a circadian rhythm?
A biological rhythm that lasts around 24 hours
What is the main circadian rhythm?
Sleep-wake cycle
What drives biological rhythms?
Internal body clock
What is the internal body clock that drives biological rhythms?
Endogenous pacemaker
What are external changes in the environment that drives biological rhythms?
Exogenous zeitgebers
What synchronises circadian rhythms?
Master circadian pacemaker= Suprachiasmatic nuclei (SCN) in the hypothalamus
What is photoentrainment?
Light providing the main input to the body clock
How does light impact the body clock?
Light sensitive cells in eyes detect brightness & send messages to SCN, which uses info to coordinate activity of circadian rhythm (e.g. more awake)
How many points are there when explaining the sleep-wake cycle as a circadian rhythm?
6
What is the first point of the sleep-wake cycle?
Light & dark= main external signals for sleep/wake
What is the second point of the sleep-wake cycle?
Dips and rises in key times- strong sleep = 2-4am & 1-3pm
What is the third point of the sleep-wake cycle?
Homeostatic control- tells us to sleep if awake for long
What is the fourth point of the sleep-wake cycle?
Circadian system helps keep us awake in daylight but homeostatic=sleepier
What is the fifth point of the sleep-wake cycle?
Influenced by daylight too
What is the sixth point of the sleep-wake cycle?
If left to own devices & no external cues present, it is “free running” e.g. Michel Siffre
What are two other circadian rhythms?
1) Core body temperature- lowest at 4:30am, highest at 6pm, sleep starts as temp drops
2) Hormone production- Pineal gland in brain produces & releases melatonin- peak during dark & encourages sleep
What was the aim of Michel Siffre’s study?
To study the influences on circadian rhythms
What was Michel Siffre’s procedure?
2nd study- lived in a cave (no light) for 6 month, so that the only thing influencing him was his internal body clock
What were Michel Siffre’s findings?
His natural circadian rhythm was 48 hours when young, and just over 24 hours when older (66) but with dramatic variations
What does the homeostatic drive do?
Causes increase in need for sleep, throughout the day
When is sleep drive strongest?
Between 2-4am and between 1-3pm
What is melatonin?
Produced by the pineal gland in the brain in response to darkness (sleepier)
How long are ‘free running’ circadian rhythms?
24-25 hrs
What do some suggest is the most important factor in circadian rhythms other than light?
Body temperature more important as it sets timings for cells
What support is there for the importance of light in circadian rhythms (criticises temp importance)?
Extremes of daylight in polar regions (Antarctica) responsible forvariations in circadian hormone release
What is the importance of individual difference in circadian rhythms?
Research supports that they can vary between 13 and 65 ours- innately different on when their circadian rhythms reach their peak too
What research challenges circadian rhythms?
Dim artificial light doesn’t affect circadian rhythms- early study findings
What research challenges the criticism of circadian rhythms?
Zeisler et al (1999) suggested it isn’t true, by altering circadian rhythms by 2-4 hrs each way using dim artificial lighting
What real world application is there for circadian rhythms?
Chronotherapetics- Understand how timing affects drug treatments, better for patient now
What are ultradian rhythms + example?
Biological rhythms that last under 24 hrs e.g. 5 stages of sleep
What are infradian rhythms + example?
Biological rhythms that last over 24 hrs e.g. menstrual cycle
What research supports the explanations of ultradian/infradian rhythms?
Tucker (2007)- sleep lab experiment. found differences in stages of sleep and ease of sleep so concluded differences must be biological, not environmental
What are 2 strengths of Tucker’s study as support for ultradian/infradian rhythms?
1) Control over variables- lab study
2) Showed nature of rhythm is biological, not environmental
What is a limitation of Tucker’s study as support for ultradian/infradian rhythms?
Different environment may alter sleep as it is artificial & individual differences
What is the research support for BRAC? (Ericsson 1980)
Studied elite violinists, athletes & musicians and found they practised for 90 mins segments and had naps to recover, which was consistent with Kleitmans BRAC cycle
What are endogenous cues?
Internal cues
What are exogenous cues?
External cues
What is an examples of endogenous cues?
Hormones
What is an examples of exogenous cues?
Phermones
Why are studies about the menstrual cycle problematic when evaluating infradian rhythms problematic?
Confounding variable- no cause and effeect
What is the real world application of research into the area?
Seasonal affective disorder
What is an advantage of real world application of research into rhythms?
Treatment for many is now available
What is an disadvantage of real world application of research into rhythms?
Treatment can have side affects
What are 3 ways that research into ultradian rhythms has improved understanding of age-related changes in sleep?
1) Slow-wave sleep (SWS)
2) Can explain why elderly people are slower/other age related conditions
3) Development of treatment for medical conditions
What are endogenous pacemakers?
Internal biological clocks in the brain e.g. SCN
What are exogenous zeitgebers?
Environmental events that influence the biological clock e.g. light
What does endogenous mean?
Anything whose origins are within the organism
What do endogenous pacemakers do?
Allow us to keep pace with changing cycles in the environment
What is the suprachiasmatic nucleus and where is it?
Most important endogenous pacemaker, in the hypothalamus
What does the SCN do?
Generates the body’s circadian rhythm
What influences the SCN in setting our body clock?
Light
What’s the link between the SCN and melotonin?
The SCN regulates the manufacture & secretion of melatonin in the pineal gland
What does melatonin do?
Induces sleep by inhibiting the brain mechanisms that promote wakeness
What is the link between the SCN & pineal gland to the outside world?
Their activity must be synchronised with the light-dark rhythm of the world outside
Explain light as an exogenous zeitgeber
Receptors in SCN sensitive to light changes as light resets internal body clock daily
Rods and cones in retina detect light & the protein melanopsin takes signals to SCN
Explain social cues as an exogenous zeitgeber
Meal times & social activities
Blind people have same circadian rhythm due to social cues
What research did Morgan (1995) do?
Research with hamsters & the SCN
What was Morgan’s aim?
To investigate the importance of the SCN as an endogenous pacemaker
What was Morgan’s procedure?
Bred a strain of hamsters with abnormal circadian rhythms (20 hrs not 24)
Transplanted SCN neurons from abnormal to normal hamsters and transplanted SCN neurons from normal to abnormal too
What were Morgan’s findings?
Normal hamsters circadian rhythms became abnormal and vice versa for originally abnormal circadian rhythmed hamsters
What do Morgan’s findings suggest about the role of the SCN?
Confirms their importance in determining the circadian rhythm in animals
What further evidence is there for the role of exogenous zietgebers from Burgess et al (2003)
Exposure to bright light before east to west flight decreases time needed to adjust to local time on arrival
Suggests light exposure prior to flight allows travellers to arrive with circadian rhythms already partially re-entrained to local time
How does the research by Vetter et al (2011) show light as the dominant zeitgeber for the SCN?
Warm artificial light vs light close to daylight (blue light) used, participants kept daily log of sleep
Warmer light= sunrise advanced by 42 mins
Blue enriched light= no 42 min adjustment- synchronised to office hours
