Discuss the role of circadian rhythms in human behaviour. (16 marks)
Outline:
Biological rhythm with 24 hour cycle, e.g. sleep/wake
Dominant exogenous zeitgeber – external influence that entrains biological rhythm – light
Light received by photoreceptors optic chiasm, located below SCN: main endogenous
pacemaker
SCN resets in light, synchrony between body and environment, photo-entrainment
SCN stimulates pineal gland, melatonin, induces sleep
Melatonin inhibited by light, more wakeful in daylight hours
Core body temperature, peaks at 6pm, lowest at 4am
Affects human behaviour, associated with cognitive performance
Gupta, IQ better at 7pm than 9am or 2pm
Evaluation:
P: Siffre
E: cave no light for two months, 25 hours
A: internal body clock strong regular, need entrainment by zeitgebers for synchrony with
environment
C: only one participants, not universal generalisable
L: repeated age 60, 48 hours, age
P: too much emphasis on light
E: Luce and Segal, social cues more important, people in arctic regular despite no/all light
L: Miles, man blind from birth, 25 hour cycle despite social cues, light dominant zeitgeber
P: practical applications to shift workers
E: Czeisler, Utah chemical plant, stress health and sleep problems
A: changing shifts to move forwards every 21 days, rather than back every 7 days, employee
output and satisfaction increased
L: can increase worker productivity, health and satisfaction
Outline:
Biological rhythm with 24 hour cycle, e.g. sleep/wake
Dominant exogenous zeitgeber – external influence that entrains biological rhythm – light
Light received by photoreceptors optic chiasm, located below SCN: main endogenous
pacemaker
SCN resets in light, synchrony between body and environment, photo-entrainment
SCN stimulates pineal gland, melatonin, induces sleep
Melatonin inhibited by light, more wakeful in daylight hours
Core body temperature, peaks at 6pm, lowest at 4am
Affects human behaviour, associated with cognitive performance
Gupta, IQ better at 7pm than 9am or 2pm
Evaluation:
P: Siffre
E: cave no light for two months, 25 hours
A: internal body clock strong regular, need entrainment by zeitgebers for synchrony with
environment
C: only one participants, not universal generalisable
L: repeated age 60, 48 hours, age
P: too much emphasis on light
E: Luce and Segal, social cues more important, people in arctic regular despite no/all light
L: Miles, man blind from birth, 25 hour cycle despite social cues, light dominant zeitgeber
P: practical applications to shift workers
E: Czeisler, Utah chemical plant, stress health and sleep problems
A: changing shifts to move forwards every 21 days, rather than back every 7 days, employee
output and satisfaction increased
L: can increase worker productivity, health and satisfaction
