Unit 4Bio Rhthyms1 Physiological Psychology Biological Rhythms

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Unit 4Bio Rhthyms3 What is a bio-rhythm? Which of the following diagrams would you consider to be showing a rhythmic pattern?

Unit 4Bio Rhthyms4 What is a biological rhythm? A periodic change in the behaviour or physiology of animals and plants –(eg sleep, hibernation and migration) People that study biological rhythms are known as ‘chronobiologists’

Unit 4Bio Rhthyms5 The Main Bio-Rhythms 1 Ultradian Rhythm (less than 24 hours) 2 Circadian Rhythm (24 hours) 3 Infradian Rhythm (1 month) 4 Circannual Rhythms (1 year)

Unit 4Bio Rhthyms6 The Circadian Rhythm A daily rhythmic activity cycle, based on 24-hour intervals

Unit 4Bio Rhthyms7 The Circadian Rhythm We have evolved to fit the 24 hour clock Even single celled organisms display a 24 hour cycle Mammals have evolved to fit the cycle –Nocturnal v Diurnal There are around 100 types of Circadian Cycles (Green 1994) Most commonly known is sleep wake cycle –Although this is different in infancy

Unit 4Bio Rhthyms8 Development of Circadian Rhythms in Infancy At what point would you say the infant’s rhythm becomes established?

ACTIVITY Describe your average day: What time do you wake? How do you feel? When do you get hungry? When do you have lunch? When do you start to feel tired? When do you go to sleep? Unit 4Bio Rhthyms9

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Unit 4Bio Rhthyms11 morning or night person? The Night Owl Shows “morning syndrome” i.e. awakens as day goes on … Goes to bed late – midnight or later Wakes late as possible in morning Feels ‘ill’ if has to get up at 6am Feels tired during the day due to too little sleep The Morning Lark Doesn’t show morning syndrome Tends to wake early before 7am Active soon after waking Struggles to stay up late Can fall asleep fast if goes to bed early e.g. 9pm

Unit 4Bio Rhthyms12 Other Circadian Rhythms Temperature regulation Cognitive functioning Pain tolerance Certain illnesses are worse at different times e.g. hay fever in the morning, or late at night Chronotherapeutics address this

Unit 4Bio Rhthyms13 Key Study: Siffre Spent some time in a cave Absence of all time givers Extended his circadian cycle to approx 27 hours Spent 179 days in cave (but he thought 151!) However, Lavie (2001) puts the shift at only a few minutes using careful controls What day is it?

Unit 4Bio Rhthyms14 The Circadian Shift

Unit 4Bio Rhthyms15 But what gives us our sense of time? Exogenous Zeitgeber Outside the body External cues –(e.g. your alarm clock) Environmental stimuli –(e.g. daylight, temperature change) Endogenous Pacemaker Within the body Specific bio-chemical changes –(e.g. melatonin, SCN, pineal gland)

Unit 4Bio Rhthyms16 Suprachiasmic Nucleus (SCN)

Unit 4Bio Rhthyms17 The Suprachiasmic Nucleus

Unit 4Bio Rhthyms18 Endogenous Pacemakers small cluster of cells in our hypothalamus called the: Suprachiasmatic nucleus (SCN). linked to our visual system influenced by the amount of light we detect.

Unit 4Bio Rhthyms19 Endogenous Pacemakers SCN can in turn cause the pineal gland to produce a hormone called melatonin This can make you feel sleepy.

Unit 4Bio Rhthyms20 24 Hours of Melatonin Secretion Ok, what conclusions would you draw from this chart. Can you explain why this happens?

Unit 4Bio Rhthyms21 The general scientific test for endogenous rhythms 1.Place the organism into an environment devoid of all external patterns 2.(e.g. constant light and temperature) 3.Observe if the rhythmic pattern continues. 4.This would be in a laboratory situation where a constant environment is maintained. 5.Endogenous rhythms are usually coded in the organisms DNA, and hence the endogenous pattern is usually inheritable.

Unit 4Bio Rhthyms22 DeCoursey et al (2000 ) destroyed the SCN in some chipmunks. found that these chipmunks were much more active at night however they were also more likely to be taken by nocturnal predators Support for the ecological theory in sleep (more on that later) I may look cute, but just because researchers were a bit cruel to me, you can’t use that as an evaluation!

Unit 4Bio Rhthyms23 Internet Resources an interactive resource on sleep-wake cycle

Unit 4Bio Rhthyms24 Watching TV late at night? Staying indoors during the winter? Solar eclipse? What about the following: Summer in Norway? Flying from San Francisco to London?

Unit 4Bio Rhthyms25 Disruption of Circadian Rhythms Jet Lag (Spitzer et.al.) Body is out of phase You think/feel it’s a different time. Worse travelling from the west to an eastern time zone –(e.g. Los Angeles to London)

Unit 4Bio Rhthyms26 Prevention of Jet Lag Using artificial doses of melatonin can reduce the effect of jet lag

Unit 4Bio Rhthyms27 Internet resources levelpsychology.co.uk/online/a2/chapter04/i ntex2.asphttp:// levelpsychology.co.uk/online/a2/chapter04/i ntex2.asp An interactive resource on jet lag

Unit 4Bio Rhthyms28 Common Effects of Shift Work Lack of communication between staff Lack of ‘teamwork’ Poorer concentration on duty tasks Unsafe conditions Stress Shift lag

Unit 4Bio Rhthyms29 Shift Lag Mental symptoms: –Increased irritability –Overly emotional –Forgetfulness Physical Symptoms: –Fatigue –Loss of energy –Tiredness

Unit 4Bio Rhthyms30 Key Studies: Monk & Folkard (1985) Interviewed workers who regularly changed shift Found changing shifts was better for for: Subjective wellbeing Productivity

Unit 4Bio Rhthyms31 Key Studies: Czeisler (1982) Workers at a chemical plant in Utah took 16 days to adjust Conclusion; workers should move forward in time (clockwise) Job satisfaction increased Productivity rose Accident rates declined Workers report more satisfaction in leisure time

Unit 4Bio Rhthyms32 Infradian Rhythms for more than one day –e.g. the 28 day menstrual cycle, Tied in closely to the lunar month (the only external cue). Evolutionary adaptation? nocturnal predation

Unit 4Bio Rhthyms33 Menstruation Levels in female sex hormones change Ovulation Pre-menstrual syndrome –(changes in female sex hormones) Menstrual synchrony –(pheromone cues)

Unit 4Bio Rhthyms34 Key study: Rienberg (1967) Studied girl in cave for 3 months Menstrual cycle shortened to 25.7 days Took a year to get back to her normal cycle of 27 days (By the way, her day lengthened to 24.6 hours – support for Siffre)

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Unit 4Bio Rhthyms36 The Ovulation Cycle

Ultradian rhythms These are rhythms that are shorter than a day. Such rhythms occur during sleep, but other ultradian rhythms include excretion from the kidneys and heart rate. People addicted to nicotine will show an ultradian rhythm — smoking! Unit 4Bio Rhthyms37

Ultradian rhythms in sleep Electroencephalogram (EEG) recordings have revealed that the brain is still active during sleep, but different states of awareness have distinct patterns of electrical activity associated with them in the normal individual. Wakefulness, the immediate pre-sleep stage, light sleep, deep sleep and periods of dreaming (REM sleep) can all be identified through EEG recording – all ultradian rhythms! Unit 4Bio Rhthyms38

Unit 4Bio Rhthyms39 Circannual Rhythms Male hamsters testosterone levels change over the year Breeding season triggered by longer days Lesions in the SCN disrupt this Testosterone is secreted all year! (Rusak & Zuker 1975)

Unit 4Bio Rhthyms40 Fertility and Summer Reinberg (1967) study in 600 german schoolgirls They tend to start their menstruation during winter months Stable menstrual cycles occur more in summer, hence more conceptions

Unit 4Bio Rhthyms41 Seasonal Affective Disorder (S.A.D.) Lack of daylight Increases melatonin Fatigue Disordered sleep patterns Risk of depression Treated with UV light and/or melatonin therapy. –For more info follow the link: