PAPER 2 - BIOPSYCHOLOGY - circadian, ultradian and infradian rhythms

Question 1

what is a circadian rhythm?

Answer 1

• a type of biological rhythm
• 24-hour cycle
• regulates body processes e.g. sleep-wake cycle and changes in core body temperature

Question 2

what was the study by Siffre?

Answer 2

• wanted to study the effects of his own biological rhythms
• subjected himself to long periods of time underground
• had no external cues to guide his rhythms (daylight/clocks/radio)
• only thing influencing his behaviour was his body clock

Question 3

what were the findings of the study by Siffre?

Answer 3

• after his first underground study of 61 days, he resurfaced on 17th September thinking it was 20th august
• second study of 6 months, his natural circadian rhythms settled to just over 24 hours

Question 4

what are the limitations of the study by Siffre?

Answer 4

still wears head lamp, could influence body clock, artificial light (turned off when asleep, turned on when awake)

Question 5

what are the strengths of the study by Siffre?

Answer 5

supports free running body clock

Question 6

what is homeostatic drive?

Answer 6

causes increase in need for sleep throughout the day

Question 7

what is the sleep-wake cycle affected by?

Answer 7

daylight

Question 8

when is sleep drive strongest?

Answer 8

between 2-4am and 1-3pm

Question 9

where is melatonin produced and why?

Answer 9

produced by pineal gland in response to darkness

Question 10

what is a free-running circadian rhythm?

Answer 10

• 24-25 hours
• cycle unaffected by external stimuli

Question 11

what are the strengths of temperature affecting circadian rhythms?

Answer 11

• body temperature fluctuates on a 24-hour circadian rhythm
• even small changes in body temp sends powerful signals to body clocks
• Buhr found these changes in set temp in cells in body

Question 12

what are the limitations of temperature affecting circadian rhythms?

Answer 12

extremes of daylight found in polar regions of the world may be responsible for circadian hormone release

Question 13

what is the research support of the importance of light on the sleep-wake cycle?

Answer 13

• after 3 months of continuous darkness, the pattern of cortisol levels changed to peaking at noon rather then when they woke up
• extremes of daylight found in polar regions may be responsible for circadian hormone release

Question 14

what is the research criticising the importance of light on the sleep-wake cycle?

Answer 14

other research using scientific communities in the Arctic who would be subject to similar, prolonged winter darkness found no such disruption of cortisol release patterns

Question 15

what research is there to support research that challenges circadian rhythms?

Answer 15

dim, artificial light wouldnt affect circadian rhythms - early study findings

Question 16

what research is there to criticise the research that challenges circadian rhythms?

Answer 16

research suggests that dim artificial light actually has been found to alter circadian rhythms by 2 hours each day