AQA BioPsychology 4.2.2

1. AQA BioPsychology 4.2.2 Biological rhythms

2. Recap - Key Concepts • Biological rhythms: regular variations in the biological activity of living organisms, such as sleep, body temperature, alertness, neurotransmitter levels, etc. • 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: 24 hrs periodicity • Ultradian rhythms: happen often within 24 hrs (sleep) • Infradian rhythms: take longer than 24hrs (menstruation)

3. Infradian rhythms • Cycles that are longer 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 5 mins for 5 things - List details that you remember from the menstrual cycle from GCSE Biology (PSHE)

4. Menstrual Cycle • Menstruation usually happens every 28 days – this is less than one cycle in 24 hours • Infra = below • Diem = day

5. Rising levels of oestrogencause the ovary to develop and release an egg. Progesterone leads to the thickening of the womb lining. If fertilization does not take place the womb lining comes away resulting in the menstrual flow

6. Mechanisms of menstration • The pituitary gland governs the phases of the menstrual cycle by activating hormones which cause changes in the endometrium (the walls of the uterus) and the preparation of the ovum • Timonen et al (1964) showed that conceptions increased during lighter months, and was less during the darker months

7. Exogenous zeitgebers and menstruation • It has been observed that menstruation starts for the first time mainly in winter, because the pineal gland is affected by melatonin secretion as is the reproduction system in general

8. Exogenous zeitgebers and menstruation The synchronisation of menstrual periods attributes to the hypothesis of the unconscious detection of chemical scents called pheromones secreted at certain times during the menstrual cycle (Sabbagh & Barnard, 1984; Russell et al., 1980)

9. Exogenous zeitgebers and menstruation Stern & McClintock (1998) Studied 29 women with irregular periods Pheromones collected Put on top of lips!!! 68% of the women experienced changes in their menstrual cycle bringing them in synch with the odour donor!!

10. Evaluation • Many factors could change a woman’s menstrual cycle including diet, stress etc. Length of cycles change regularly • Small sample sizes means lack of population validity • PPts have to self report when their menstruation starts – there are lots of potential sources of confounding variables

11. Evaluation Synchronised menstruation could have evolutionary advantages - offspring born at the same time could be cared for collectively increasing the chances of survival However if everyone is fertile at the same time it would increase competition for the fittest males – this could cause problems

12. Seasonal affective disorder (SAD): Seasonal changes in behaviour can also be found in human beings. Individuals may feel depressed during winter, and happier during summer. One suggestion is that the absence of light increases melatonin, which in turn reduces serotonin which is associated with depression. SAD is mostly seen in more northern than southern countries. Light therapy may help reduce the symptoms of SAD (Rosenzweig et al. 1999).

13. Evaluation Phototherapy - using light to help people with SAD can be effective. It is believed to help reset melatonin levels It relieves symptoms for 60% of sufferers but a placebo also relieved the symptoms of 30% of sufferers,

14. Task Use your text books to complete the work sheet

15. STAGES OF SLEEPLink to Spec 4.2.2 Ultradian Rhythms

16. STAGES OF SLEEP:Link to Spec 4.2.2

17. What are Ultradian Rhythms? • Biological rhythms with more than one cycle in 24 hours. (P) Ultra =more than Diem = day • Within a night’s sleep, we move systematically through 5 different phases of sleep, Each cycle taking approximately 90 minutes. (E) • Therefore a single sleep cycle is an Ultradian rhythm. (E) These can be measured using an EEG

18. EEG MACHINE

19. Wave Glossary Frequency (hz) Amplitude = size of wave

20. AWAKE EEG shows HIGH FREQUENCY and LOW AMPLITUDE waves known as ALPHA waves (less than 12 hz) ALERT

21. STAGE 1 ALPHA and BETA waves decrease, THETA waves begin which are lower frequency, greater amplitude (4-8 hz) RELAXED, EASY TO WAKE Lasts about 15 mins

22. Sleep stages 1-2 Described as light sleep The person can be easily awoken Brain activity becomes slower and more rhythmic, moving from alpha to beta waves

23. STAGE 2 From BETA in to THETA waves, some SLEEP SPINDLES (increased frequency) and K COMPLEXES (increased amplitude) 8-15 hz LIGHT SLEEP Lasts about 20 mins

24. STAGE 3 THETA waves continue, DELTA waves begin – lower frequency, greater amplitude. 2-4 hz DEEP SLEEP, SOME DREAMING Lasts about 15 mins

25. STAGE 4 Mainly DELTA waves 0.5-2 hz larger amplitude VERY DEEP SLEEP DIFFICULT TO WAKE UP SLEEPWALKING Lasts about 30 mins

27. Stage 5 REM SLEEP BETA waves return, similar to relaxed AWAKE state 12 hz+ VIVID DREAMING (Kleitman 1957) TEMPORARY MUSCLE PARALYSIS PARADOXICAL SLEEP. Lasts about 10-60 mins

28. Dreaming REM

29. Up and down the “sleep escalator” • 1, 2, 3, 4, 3, 2, REM • 2, 3, 4, REM • 2, REM • 2, REM • 2, REM • 10, 10, 40, 60 (how long the REM cycles are)

30. Brain Waves • Beta • Alpha • Theta • Delta

31. Evaluation Dement and Kleitman studied ppts in a sleep lab and found evidence for all the different stages of sleep. REM was associated with dreaming REM is a distinct ultradian rhythm