Ultradian and Infradian Rhythms Ultradian rhythms How do

Ultradian and Infradian Rhythms

Ultradian rhythms How do we measure this? Muscles, electrical activity, eye movements Guess how they match up • Electroencephalographs (EEGs) • Electro-Oculograms (EOGs) • Electromyograms (EMGs)

Outline or more examples of Ultradian rhythms. (4 marks) Ultradian rhythms are rhythms that have a cycle length of more than one cycle every _____. The sleep cycle is an ultradian rhythm and most people have _____ cycles of sleep that last approximately ___ minutes each night. There are two classifications of sleep, _____ and _____ consists of 4 stages and REM sleep is the final stage of the sleep cycle. In the first two cycles, the sleeper descends through the lighter stages of sleep (stages 1 -3) into the _____ stage of sleep (stage 4), then onto ____ sleep for around ____ minutes. In the last 3 cycles, the sleeper moves from stage 2 straight to REM and periods of REM get increasingly longer.

Outline or more examples of ultradian rhythms. (4 marks) Ultradian rhythms are rhythms that have a cycle length of more than one cycle every 24 hours. The sleep cycle is an ultradian rhythm and most people have five cycles of sleep that last approximately 90 minutes each night. There are two classifications of sleep, NREM & REM. NREM consists of 4 stages and REM sleep is the final stage of the sleep cycle. In the first two cycles, the sleeper descends through the lighter stages of sleep (stages 1 -3) into the deeper stage of sleep (stage 4), then onto REM sleep for around 10 minutes. In the last 3 cycles, the sleeper moves from stage 2 straight to REM and periods of REM get increasingly longer.

Research activity 1. Dement and Kleitman (1957) 2. Wehr (1992) 3. Ekirch (2001) Read through the study you have been asked to look at and ground it onto MWB. 7/8

Sleep is measured in a laboratory • Why does this way of studying the ultradian rhythm give objective and replicable evidence? • Also comment on why objectivity and replicability are positive qualities for evidence to have. Annotate points in pack

IDA Example for Ultradian Rhythms: The Sleep Cycle The Point: Biological determinism Nature nurture Reductionism Explain the Point: Little Free will Simplistic- ignores cultural/societal factors Simplistic- Does not fully exaplain external influences So What? Research methodology evaluation Implications Usefulness 8

IDA Example for Ultradian Rhythms: The Sleep Cycle The Point: The research into the sleep cycle shows that the rhythm is controlled purely by… Biological factors Explain the Point: This is because the research suggests that external factors have… Little influence over the sleep cycle, suggesting biological determinism So What? The fact that the rhythm is biologically controlled has implications for the way the sleep cycle is… researched Most of the research involves wiring participants up to an EEG to measure their brain waves during the various stages of sleep. This has been beneficial to our understanding of the sleep cycle as it leads to… Precise measurement of the ultradian rhythm

Infradian Rhythms • The Menstrual cycle • True or False

Menstrual cycle- T/F 1. The average a girl starts having menstrual periods is between 11 and 14 2. The average menstrual cycle is 28 days long. 3. Day 1 on the menstrual cycle is when the women has a period. 4. On average, ovulation occurs on day 14 (based on a 28 day cycle) 5. The menstrual cycle is controlled solely by hormones 6. Low weight is correlated with early start of periods 7. The most common cause of a missed period is taking prescription medication 8. Women who spend a lot of time together will tend to have their menstrual cycles synchronize over time.

Answers 1. 2. 3. 4. 5. 6. 7. 8. True False- Exogenous factors too (Pheromones) False- Being over weight is False- Pregnancy Maybe?

5 mins! Research and define – divide between people on your table Follicle stimulating hormone Oestrogen Luteinizing hormone Progesterone HCG Pheromones

Now you have defined the terms: 10 mins! Individually create a flowchart/diagram/mindmap to represent the outline of infradian rhythms that is in your pack. Remember to include pheromones

Research evidence Read the findings on page 9 and ground the evidence Extension: Read the article Highlight any agreement/disagreement to the studies and add to your packs.

• Timonen et al (1964) found that women were far more likely to conceive in lighter months of the year than in darker months. This was attributed to the effects of light on the pituitary gland, which exerts influence on the cycle via the ovaries. • Research in Germany showed that the onset of menstruation (menarche) was more likely to occur in the winter and menarche is reached earlier by blind girls than sighted girls.

Nature vs Nurture 1. What evidence is there for endogenous pacemakers (nature) in Infradian rhythms? 2. What evidence is there for exogenous zeitegebers (nurture) in Infradian rhythms? 3. Which evidence is stronger? 4. What does this suggest about the role of nature/nurture in Infradian rhythms?

Discuss • How could what we have discussed be explained through the evolutionary approach?

Evolutionary advantage • Bentley (2000) believed that synchronisation between women living in close proximity would ensure that the women would conceive and give birth at similar times. This would be beneficial since they could share breast feeding, a behaviour observed in other species. • Similarly, Mc. Clintock (1971) found that women who work in a mostly male environment have shorter menstrual cycles. In the past this would be of evolutionary advantage since it would provide more opportunities for pregnancy.

Choose an IDA • Nature vs Nuture • The evolutionary approach Write up in packs

Determinism as wider evaluation Premenstrual syndrome • PMS or Premenstrual syndrome is a disorder that affects many women during the week before menstruation begins. Symptoms can include acne, anxiety, depression, food cravings, fatigue, headaches, insomnia, water retention, mood swings and aggression Ms English was a woman who drove her car into her married lover after an argument, killing him. Her defence team used PMS as a legal defence and she was ultimately placed on Probation. • This deterministic approach assumes she had no free will of her own or any control and could therefore not be held liable for her actions. Why are infradian rhythms deterministic? Apply this to the above scenario. Explain one advantage and one disadvantage of taking this deterministic approach.