Biological rhythms: infradian and ultradian rhythms

Question 1

What is an infradian rhythm:

Answer 1

• biological rhythm that has a frequency of less than one cycle in 24 hours
• menstruation and seasonal effective disorder (SAD)

Question 2

What is an ultradian rhythm?

Answer 2

• biological rhythm with a frequency of more than one cycle in 24 hours
• stages of sleep

Question 2

What is the menstrual cycle?

Answer 2

• cycle is when woman womb starts lining= 1st day of period, to day before her next period
• lasts 28 days

Question 3

Hormone changes of the menstrual cycle?

Answer 3

• rising levels of oestrogen= ovary develops an egg and releases it
• after ovulation progesterone= womb lining grows thicker so ready for pregnancy
• if pregnancy doesn’t happen egg absorbed and lining comes away

Question 4

Synchronisation of the menstrual cycle: Stern and Mcklintock procedure

Answer 4

• studied 29 women with history of irregular periods
• pheromones gathered from 9 women in diff stages of their cycle
• pads under armpits worn for at least 8 hours
• pads frozen and rubbed on upper lip of other pp

Question 5

Synchronisation of the menstrual cycle: Stern and Mcklintock findings

Answer 5

• pads from the start of the cycle rubbed on 20 of pp
• then given pad from the second day and so on…
• found 68% of women experienced changes to their cycle bringing them closer to their ‘odour donor’

Question 6

What is seasonal affective disorder? (SAD)

Answer 6

• depressive disorder with a seasonal pattern
• ’ winter blues’= triggered when daylight hours become shorter

Question 7

How is SAD infradian as well as circadian?

Answer 7

• infradian= yearly cycle (circannual)
• circadian= SAD may be due to disruption to sleep/wake cycle because of longer days during winter

Question 8

what are the hormones that cause SAD?

Answer 8

• during the night the pineal gland excretes melatonin until morning= increase in light
• lack of light in winter= excretion process is longer
• knock on effect to the production of serotonin= linked to depressive symptoms

Question 9

what is the stages of sleep cycle?

Answer 9

• ultradian rhythm
• 5 stages of sleep that together span 90 minutes and continues throughout the course of the night
• characterised by diff levels of brain activity shown by EEG’s

Question 10

Stage 1 and 2

Answer 10

• light sleep and easily woken
• brain waves are high frequency and short amplitude= alpha waves
• stage 2= alpha waves but random changes called sleep spindles

Question 11

Stage 3 and 4

Answer 11

• deep sleep or slow wave sleep
• brain waves are delta= lower frequency and higher amplitude
• hard to wake

Question 12

Stage 5= REM sleep

Answer 12

• body is paralysed but brain is pretty much awake
• produce theta waves
• rapid eye movements are produced (REM)
• dreams usually experienced

Question 13

Infradian rhythms evaluation: strength evolutionary bias

Answer 13

• synchronisation has evolutionary value
• women who menstruate together can become pregnant at the same time
• babies who lost their mothers are able to have milk
• increasing their chances of survival

Question 14

Infradian rhythms evaluation limitation: methodological limitations

Answer 14

• stress changes in diet and exercise all affect menstrual cycle
• these are all confounding variables
• any synchronisation could have occurred by chance
• hard to replicate findings

Question 15

Ultradian rhythms evaluation: strength improved understanding

Answer 15

• sleep scientists found the SWS reduced with age
• Growth hormone produced in SWS, so reduced in old people
• this can lead to reduced alertness
• drugs and relaxation can be used to increase SWS

Question 16

Ultradian rhythms evaluation: limitations individual differences

Answer 16

• Tucker et al. found big differences between duration of each sleep stage (especially 3+4)
• likely biologically determined
• hard to describe ‘normal’ sleep in meaningful way