Biological rhythms: Infradian and Ultradian rhythms

Question 1

What is an example of an infradian rhythm

Answer 1

• the menstrual cycle

Question 2

Describe what occurs in the menstrual cycle

Answer 2

• during each cycle rising levels of oestrogen cause the ovaries to develop n egg and release it (ovulation)
• after ovulation the hormone progesterone helps the womb lining to grow thicker
• if pregnancy does not occur the egg is absorbed into the body, the womb lining ext]its the body

Question 3

Outline Stern and McClintock’s study

Answer 3

• it involved 29 women with a history of irregular periods, samples of pheromones were gathered from 9 of the women at different stages of their menstrual cycles, via a cotton pad placed under the armpits
• pads were worn for 8 hours, then treated with alcohol and frozen to be rubbed on the upper ip of the other ppts
• McClintock found that 68% of the women experienced changes to their cycle

Question 4

Why can SAD be classed as a circadian rhythm

Answer 4

• the experience may be due to the disruption of the sleep/wake cycle and this can be attributed to prolonged periods of daily darkness during winter
• psychologists have hypothesised that the hormone melatonin is implicated in the cause of SAD

Question 5

Why have psychologists hypothesised that the hormone melatonin is implicated in the cause of SAD

Answer 5

• because during the night melatonin is secreted until dawn where there is an increase in light, however during the winter it gets brighter later meaning this secretion process lasts for longer
• this is thought to have a knock-on effect on the production of serotonin in the brain, a hormone linked to the onset of depressive symptoms

Question 6

Outline stages 1 and 2 of the Ultradian rhythm

Answer 6

• light sleep where someone can be easily awoken, at the beginning of sleep brainwave patterns begin to become slower and more rhythmic (alpha waves)

Question 7

Outline stages 3 and 4 of the Ultradian rhythm

Answer 7

• involves delta waves which are slower and have a greater amplitude than earlier wave patterns, this is deep sleep and it is difficult to wake someone up at this point

Question 8

Outline stage 5 (REM sleep)

Answer 8

• the body is paralysed, but brain activity speeds up significantly in a manner that resembles the awake brain, this part of sleep is related with the experience of dreaming

Question 9

What is a limitation of the evolutionary basis of the menstrual cycle

Answer 9

• would’ve been beneficial in the past for females to menstruate together and fall pregnant around the same time, meaning new-borns could’ve been cared for collectively
• Schank argued that this would’ve increased competition for the highest quality males and therefore lowering the fitness of potential offspring and so avoidance of synchrony would be the most adaptive evolutionary strategy

Question 10

Methodological limitation of synchronisation studies include….

Answer 10

• the fact that there are many factors effecting menstrual cycles, stress, exercise etc that may act as confounding variables

Question 11

What evidence is there to support the idea of distinct stages of sleep

Answer 11

• Dement and Kleitman monitored the sleep patterns of nine individuals, brain wave activity was recorded through EEG and the researchers controlled for the effects of caffeine and alcohol, REM was highly correlated with the experience of dreaming, ppts who woke up during dreaming reported very accurate recall of their dreams
• replications of this study showed similar results