Biological Rhythms 6 2 Biological Psychology Biological Rhythms

Biological Rhythms 6. 2 Biological Psychology

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

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

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

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

Types of Rhythms n Circadian – consistent cyclical variations that occur over a 24 hour period n Ultradian – shorter than one day n Infradian – longer than one day n 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.

Examples of Circadian Rhythms n The sleep/wake cycle n Heart rate, metabolic rate, breathing rate, body temperature all have maximum values in late afternoon and minimum values in the early morning. n 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. n The opening and closing of heliotropic plants.

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

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

Infradian Rhythms 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 Pacemaker = pituitary gland Modification by external Zeitgebers 1. Russell et al. – donor pheromones on lips of female test participants Modification by external Zeitgebers 2. Mc. Clintick et al. – the effect of male pheromones

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

Ultradian rhythms Research by…. Dement & Kleitman

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

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

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

Plenary Activity n n n 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.

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

Extension Work - Disruption of Biological rhythms – things to think about n n 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.