circadian rhythms

Question 1

what is a circadian rhythm

Answer 1

a biological rhythm that lasts about 24 hours, which regulates several bodily processes such as the sleep wake cycle and core Changes in body temp

Question 2

outline the sleep wake cycle

Answer 2

• circadian rhythms dictate when we should sleep and be awake
• controlled by the suprachiasmatic nucleus
• light and darkness are the external signals that determine when we feel the need to sleep and wake up
• it also dips and rises at different parts of the day and our strongest sleep drive is usually between 2-4 am and 1-3 pm
• the free running internal circadian clock maintains a cycle of 24-25 hours even in the absence of external cues such as light

Question 3

outline core body temperature

Answer 3

• one of the best indicators of the circadian rhythm
• its at its lowest at about 4:30 am and highest at about 6pm
• sleep occurs when the core temp begins to drop and body temp begins to rise during the last hours of sleep promoting alertness in morning
• a small body temp drop also occurs between 2-4 pm which explains sleepiness in afternoon

Question 4

discuss siffre study

Answer 4

• siffre isolated himself from all daylight by spending 6 months in a dark cave which only artificial light to help him navigate
• he had no clock or time but did have verbal contact with world
• found that his internal body clock was allowed to ‘free run’ and at first it was erratic however it eventually settled into a sleep wake cycle or 25-30 hours. he continued to fall asleep and wake up on a regular schedule however he lost track of his time spent in the cave believing it to be one month less than he had stayed in
• this suggests that in the absence of EZ’s such as natural light, circadian rhythms are roughly maintained which supports existence of internal body clock

Question 5

what is a strength of circadian rhythms (evidence)

Answer 5

supported by Siffre

Question 6

what is a limitation of circadian rhythms (case study)

Answer 6

siffres research- with himself as the only ppt it means it is unrepresentative and has low population validity. we can’t be certain that his findings in relation to the fact that exogenous zeitgeibers and endogenous pacemakers work together is valid, however siffre is a perfectly normal member of the human race so perfectly possible his findings apply to others

Question 7

what is a limitation of circadian rhythms (access to light)

Answer 7

siffre did have access to artificial light which he assumed would not affect his circadian rhythms, however, Czeizler et al managed to alter ppts circadian rhythms down to 22 hours and uo to 28 hours using artificial light alone. limitation of siffre as it may have been the artificial light maintaining his sleep wake cycle and therefore his conclusion may not be valid

Question 8

what is a strength of circadian rhythms (practical application)

Answer 8

for shift work- research has shown that night workers engaging in shift work experience a period of reduced concentration around 6 in the morning meaning that mistakes and accidents are more likely- this is a strength as research into sleep wake cycle may have economic implications in terms of how to best manage worker productivity and safety

Question 9

evaluate overall circadian rhythms

Answer 9

supporting evidence, evidence is case study, artificial light does affect rhythms, practical applications to shift work