AQA-A2 Unit 3/PSYA3: Topics AQA-A2 Unit 3/PSYA3: Topics in Psychologyin Psychology

Biological rhythms

Key Concepts 1Key Concepts 1

Biological rhythms: regular variations in the biological activity of living organisms, such as sleep, body temperature, alertness, neurotransmitter levels, etc.

Circadian rhythms: 24 hrs periodicity Infradian rhythms: more than 24hrs

periodicity Ultradian rhythms: less than 24 hrs

periodicity

Key concepts 2Key concepts 2

Endogenous pacemakers: Biological ‘clocks’ in the brain controlling biological rhythms. Most likely the suprachiasmatic nucleus in the hypothalamus

Exogenous Zeitgebers (Timegivers): External stimuli that help towards regulating biological rhythms to the outside world

Circadian rhythms 1Circadian rhythms 1

Etymology: circa (almost), dies (day)

Examples: sleep/waking, body temperature

Circadian rhythms are needed to balancing behaviour and body states to environmental changes

Circadian rhythms 2Circadian rhythms 2 Folkard et al., (1985) argues that bodily

rhythms (during circadian time) are primarily an endogenous property, which does not depend on exogenous cues. Example comes from the sleep and waking cycle. Some people may have 45 minutes of sleep each night?!, or only 5 to 6 hrs.

The effect of melatonin to serotonin, which is concentrated in a brain structure called raphe nuclei (the core group seam)

Circadian rhythms 3 Circadian rhythms 3 (in relation to (in relation to rache nuclei)rache nuclei)

Rache nuclei releases serotonin to the rest of the brain

Rache nuclei appears in the medial portion as a ridge of cells in the centre of the brain stem

Circadian rhythms 4Circadian rhythms 4 The symptoms of many illnesses fluctuate

over the 24hr cycle, such as hay fever, and are worst around dawn; heart attacks are likely to happen in the morning when blood is more prone to clotting (thickened blood)

Chronotherapeutics (Dobson, 1999): Description of drug effectiveness during night when blood is thinner in density (compactness)

Hormones such a prolactin (producing milk in women) also vary over the day

Infradian rhythms 1Infradian rhythms 1

Occurring to a period more than 24 hrs, such as the human menstrual cycle

Some of them may take place on a yearly basis and they are known as circannual rhythms, such as the migration of birds, and hibernation in squirrels bears, and hedgehogs

Infradian rhythms 2Infradian rhythms 2

Menstruation (likely to happen every 28 days). In a matter of months it gets established in the woman’s cycle. Menstruation is also influenced by environmental events. The synchronisation of menstrual periods attributes to the hypothesis of the unconscious detection of chemical scents called pheromones (relating to the physiology or the attraction of other species of the same or different sex) secreted at certain times during the menstrual cycle (Sabbagh & Barnard, 1984; Russell et al., 1980)

Infradian rhythms 3Infradian rhythms 3

The Pre-Menstrual Syndrome (PMS): The variety of behavioural and emotional effects taking place at several phases of the menstrual cycle (5 days before the onset of menstruation)

Large proportion of accidents and a decline in the quality of schoolwork were reported during the pre-menstrual interval (Dalton, 1964; Hardie, 1997)

Infradian rhythms 4Infradian rhythms 4

The pituitary gland governs the phases of the menstrual cycle by influencing changes in the endometrium (the walls of the uterus) and the preparation of the ovum

Timonen et al., (1964) showed that during lighter months conceptions increased, whereas not during darker months

Infradian rythms 5Infradian rythms 5

Menstruation in the absence of Zeitgebers: It has been observed that menstruation starts mainly in winter (for the first time), and that because the pineal gland is affected by the melatonin’s secretion and the reproduction system in general (conceptions in lighter months) (Reinberg, 1967)

Infradian rhythms 6Infradian rhythms 6

Seasonal affective disorder (SAD): Seasonal changes in behaviour can also be found in human beings. Individuals feel depressed during winter, and elated during summer. One suggestion is that absence of light increases melatonin, and what is suggested is light therapy (Rosenzweig et al., 1999). As an example, depression is mostly seen in northern than southern countries instead

Ultradian rhythms 1Ultradian rhythms 1

Shorter than 24 hrs, such as smoking, eating and drinking, renal excretion (discharging waste through kidneys), sleep (different stages studied through EEG-Electro-Encephalography), etc. (Loomis et al., 1937)

Ultradian rhythms 2Ultradian rhythms 2(Recording Sleep) (Recording Sleep)

EEG (Electro-EncephaloGraphy): It measures and records the electrical activity in a person’s brain

EOG (ElectrOculoGram) it records eye movements during sleep

EMG (ElectroMyoGram) it records muscle activity during sleep

Endogenous pacemakers and Endogenous pacemakers and exogenous zeitgebersexogenous zeitgebers

Endogenous pacemakers represent an inherited genetic mechanism towards rest, such as the ‘sleepy behaviour’ of an unborn baby that has never been exposed to the outside world (Pineal gland/Suprachiasmatic nucleus)

Exogenous zeitgebers refer to a behaviour fully controlled by the external world, such as the effect of light

The role of the pineal gland and the The role of the pineal gland and the suprachiasmatic nucleus (SCN) 1suprachiasmatic nucleus (SCN) 1

The role of the pineal gland and the The role of the pineal gland and the suprachiasmatic nucleus (SCN) 2suprachiasmatic nucleus (SCN) 2

Pineal gland: It contains light receptors that correspond to external light. Neurons in the pineal gland convert the neurotransmitter serotonin to melatonin, so sleep and waking cycles to be synchronised

Suprachiasmatic nucleus (SCN): It regulates the amount of melatonin in the pineal gland and it is also connected to the retina of the eye, controlling the light coming in. Light and melatonin are linked through the SCN

Research to biological rhythms 1Research to biological rhythms 1 Generally it is shown that the light/dark rhythm

of the outside world synchronises the pineal gland and the SCN.

Michel Siffre in 1972 went to live in a cave for 6 months. When he was awake the lights in the cave were on, when he went to bed the lights were off. His sleep/wake cycle regulated between 25 and 30 hrs (more than 24 hrs). When he reached the 179th day, his days were only 151 since he started living underground

Research to biological rhythms 2Research to biological rhythms 2

Kleitman (1963): Student partcipants went to live to an underground bunker, with no cues of light or dark. They had to choose their own sleep/wake times. Their circadian rhythms were extended between 25 to 27 hrs

Research to biological rhythms 3 Research to biological rhythms 3 (Evaluation) (Evaluation)

Research findings: Endogenous pacemakers and exogenous zeitgebers play an important role in regulating the human behaviour

Generalizability of research: Endogenous mechanisms can control sleep/waking in the absence of light/Exogenous zeitgebers use light to reset the clock of our biological rhythms

Research to biological rhythms 4Research to biological rhythms 4(Evaluation)(Evaluation)

Individual differences: Biological rhythms do not operate the same in all people, or in subjects of different parts of the world

Number of participants: Because most of the research was carried out with single participants, the findings are generalised with great care

The consequences of disrupting The consequences of disrupting biological rhythms 1biological rhythms 1

Jet lagTravelling to different parts of the world for

some days after the journey the sleep/wake cycle is disrupted (body temperature fails/body arousal may increase or decrease)

Shift workEmployees required to a shift work, normally go

to sleep when others are awake. When biological rhythm is disrupted (endogenous pacemakers/exogenous zeitgebers), sleep/wake cycle is disrupted too

Consequences of disrupting Consequences of disrupting biological rhythms 2biological rhythms 2

Research: Melatonin has been studied to treat jet lag and other desynchronisation problems (Takahashi et al., 2002)

The problems of jet lag and shift work disregulate our biological clocks from working properly. Coren (1996) argues that because of all those changes in our lives we end up sleeping 11/2 less than in a century ago

Evaluation of research on disrupting Evaluation of research on disrupting biological rhythmsbiological rhythms

Research findingsDisrupting our biological rhythms has cognitive and

emotional effects, as well as drastic consequences Methodological issuesStudies have great ecological validity, however

personality and individual differences are not controlled in those studies

Real-life significance?Does it matter? Effects on cognitive abilities, such

as attention and concentration negatively influence our intellectual and emotional well-being

SummarySummary

Biological rhythms play an important role in our sleep and wake cycle, as well as our cognitive and emotional preoccupations

Pineal gland, and suprachiasmatic nucleus relate endogenous pacemakers to exogenous zeitgebers

Disruption of biological rhythms bear catastrophic consequences

Questions to considerQuestions to consider

In 100 words outline what we mean by ‘endogenous pacemaker’

What is the name given to external events that play a role in rhythmic activities? Give an example

Discuss the association between SAD and exogenous zeitgebers?

Evaluate the research in biological rhythms

References 1References 1 Coren, S. (1996): Sleep Thieves. New York: Free PRess Dalton, K. (1964): The Premenstrual Syndrome. London:

Heinemann Dobson, R. (1999): Slaves to the rhythm. The Sunday Times

(Lifestyle), 25/04, pp. 33-34 Folkard, S., Hume, K. I., Minors, D. S., Waterhouse, J. M.,

Watson, F. L. (1985): Independence of the circadian rhythm in alertness from the sleep/wake cycle. Nature, 313, pp. 678-679

Hardie, E. A. (1997): PMS in the workplace: Dispelling the myth of the cyclic dysfunction. Journal of Occupational and Organisational Psychology, 70, pp. 97-102

Kleitman, N. (1963): Sleep and Wakefulness. Chicago: University of Chicago Press

References 2References 2

Loomis, A. L., Harvey, E. N., Hobart, A. (1937): Cerebral states during sleep as studied by human brain potentials. Journal of Experimental Psychology, 21, pp. 127-144

Reinberg, A. (1967): Eclairement et cycle menstruel de la femme. Rapport au Coloque International du CRNS, la photoregulation de la reproduction chez les oiseaux et les mammiferes. Montpelier

Rosenzweig, M. R., Leiman, A. L., Breedlove, S. M.(1999): Biological Psychology. Sunderland, MA: Sinauer Associates, Inc.

Russell, M. J., Switz, G. M., Thompson, K. (1980): Olfactory influences on the human menstrual cycle. Pharmacology, Biochemistry and Behaviour, 13, pp. 737-738

Sabbagh, K., Barnard, C. (1984): The Living Body. London: MacDonald Takahashi, T., Sasaki, M., Itoh, H., Yamadera, W., Ozone, M., Obuchi, K., Hayashida,

K., Matsanuga, N., Sano, H. (2002): Meletonin alleviates jet lag symptoms caused by an 11-hour eastward flight. Psychiatry and Clinical Neurosciences, 56, pp. 301-302

Timonen, S., Franzas, B., Wischmann, K. (1964): Photosensibility of the human pituitary. Annales Chirurgiae et Gynaecologiae Feminae, 53, pp. 156-172