unit 4bio rhthyms1 physiological psychology biological rhythms

Unit 4 Bio Rhthyms 1

Physiological Psychology

Biological Rhythms


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


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’


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)


The Circadian Rhythm

A daily A daily rhythmic rhythmic activity activity cycle, cycle,

based on based on 24-hour 24-hour intervalsintervals


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


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?



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


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


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?


The Circadian Shift


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)


Suprachiasmic Nucleus (SCN)


The Suprachiasmic Nucleus


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.


Endogenous Pacemakers

• SCN can in turn cause the

• pineal gland to produce a hormone called

• melatonin • This can make

you feel sleepy.


24 Hours of Melatonin SecretionOk, what

conclusions would you draw from this chart. Can you explain

why this happens?


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.


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!


Internet Resources

http://www.a-levelpsychology.co.uk/online/a2/chapter04/intex1.asp

an interactive resource on sleep-wake cycle


• 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?


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)


Prevention of Jet Lag

Using artificial doses of melatonin can reduce the effect of jet lag


Internet resources

• http://www.a-levelpsychology.co.uk/online/a2/chapter04/intex2.asp

• An interactive resource on jet lag


Common Effects of Shift Work

• Lack of communication between staff

• Lack of ‘teamwork’ • Poorer concentration

on duty tasks • Unsafe conditions • Stress • Shift lag


Shift Lag

• Mental symptoms: – Increased irritability

– Overly emotional

– Forgetfulness

• Physical Symptoms: – Fatigue

– Loss of energy

– Tiredness


Key Studies: Monk & Folkard (1985)

• Interviewed workers who regularly changed shift

• Found changing shifts was better for for:

• Subjective wellbeing • Productivity


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


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


Menstruation

• Levels in female sex hormones change

• Ovulation • Pre-menstrual

syndrome – (changes in female sex

hormones)

• Menstrual synchrony– (pheromone cues)


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)


The Ovulation Cycle

Ultradian rhythmsThese 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!


Ultradian rhythms in sleepElectroencephalogram (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!



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)


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


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: http://hcd2.bupa.co.uk/fact_sheets/html/sad.html

unit 4bio rhthyms1 physiological psychology biological rhythms

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