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Biological Rhythms

Biological Rhythms. 6.2 Biological Psychology. Biological Rhythms. Aims – Be able to define and give examples of different types of biological rhythms. Objectives – Describe and give examples of the following types of rhythms: Circadian Infradian Ultradian Distinguish between:

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Biological Rhythms

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  1. Biological Rhythms 6.2 Biological Psychology

  2. Biological Rhythms Aims – • Be able to define and give examples of different types of biological rhythms. Objectives – • Describe and give examples of the following types of rhythms: • Circadian • Infradian • Ultradian Distinguish between: • Endogenous factors – internal biological clocks • Exogenous factors – external zeitgebers (time givers)

  3. Starter – think back to the quiz you did last week • Are you a lark or an owl? – Think about your own biological rhythms

  4. What you need to know about Biological Rhythms • Research studies into circadian, infradian, and ultradian biological rhythms, including the role of endogenous pacemakers and exogenous zeitgebers. • The consequences of disrupting biological rhythms (eg. shift work).

  5. What is a Biological Rhythm? It is a cyclical variation over some period of time in physiological or psychological processes.

  6. Types of Rhythms • Circadian – consistent cyclical variations that occur over a 24 hour period • Ultradian – shorter than one day • Infradian– longer than one day • Pair Activity – with a partner, write down examples of rhythms in nature. Try to identify the type of rhythm based on how often it occurs.

  7. Examples of Circadian Rhythms • The sleep/wake cycle • Heart rate, metabolic rate, breathing rate, body temperature all have maximum values in late afternoon and minimum values in the early morning. • Hormone concentrations also vary in the body over the course of the day. In women prolactin – a hormone that stimulates milk production – peaks at night. • The opening and closing of heliotropic plants.

  8. Circadian rhythms External control: Modification by Zeitgebers Endogenous control: Pacemaker (SCN) Research by: Fulton & Bailey Jouvet (rats) Inouye & Kawamura (rats) Ralph et al (mutant hamsters) Research by: Michel Siffre (cave) Aschoff & Wever (bunker)

  9. Examples of Infradian Rhythms • These rhythms occur less than once every 24 hours. • Hibernation in squirrels • Human menstrual cycle • Migration of birds

  10. Infradian Rhythms Modification by external Zeitgebers 1. Russell et al. – donor pheromones on lips of female test participants Regular production of hormones (FSH and LH) by the pituitary gland over a 28 day period, causes regular thickening and shedding of the uterus wall, together with ovulation (egg maturation and release) Menstrual cycle: Endogenous control Modification by external Zeitgebers 2. McClintick et al. – the effect of male pheromones Pacemaker = pituitary gland

  11. Examples of Ultradian Rhythms • These have a frequency of more than one complete cycle every 24 hours. • Stages during sleep.

  12. Ultradian rhythms Research by…. Dement & Kleitman

  13. Endogenous Pacemakers • Endogenous pacemakers = Internal Biological Clocks – these probably represent an inherited genetic mechanism. • For example, regular rhythms of activity and rest can be observed in unborn human embryos. These rhythms are controlled internally by biological mechanisms.

  14. Exogenous Zeitgebers = External time givers • Biological rhythms have to respond to zeitgebers, such as light, if the behaviour they control is to be fully coordinated with the external world • The role of light – fine-tuning bodily rhythms has been studied extensively. • Can you think of any other external time givers that could affect your biological clock?

  15. Ultradian Rhythms • Take less than 24 hours • E.g. the Sleep Stages cycle Biological Rhythms Infradian Rhythms • Take longer than 24 hours • E.g. the menstrual cycle Circadian Rhythms • Take just 24 hours • E.g. the Sleep –wake cycle

  16. Plenary Activity • Think of examples of two biological rhythms that could be reset by exogenous zeitgebers (external time givers). • What endogenous pacemakers (internal biological clocks) do you think could be controlling these rhythms? • For each example give the type of rhythm – circadian/ infradian/ ultradian.

  17. Homework • Using textbooks and/or Internet – Make a note of research into biological rhythms, and choose one study to describe as follows: • Aims – include type of rhythm and purpose of study • Procedure (Method) • Results (Findings) • Conclusions • Criticisms (at least one positive and one negative)

  18. Extension Work - Disruption of Biological rhythms – things to think about • Jet Lag – what happens when you travel East to West, or West to East? Which is easier? - Investigate this question by asking friends who have travelled and bring your results to lesson. • Shift work – What happens to workers who have to change shifts? Is it easier to change forwards or backwards in time? – Find someone who does shift work and ask them.

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