sleep and wake cycle -circadian rhythm Flashcards
What is the difference between endogenous pacemakers and exogenous zietgebers?
EP- internal body clocks that keep biological processes on time
EZ- external cues that entrain internal body clocks, altering body clocks to match the environment
What is a circadian rhythm?
What do we have circadian rhythms for? (3)
Biological rhythm that lasts around 24 hours
Regulating sleep and wake, the release of hormones, varying our body temperature and blood pressure
What is the sleep wake cycle?
What must there be to keep this pattern?
Pattern of sleep and wakefulness that repeats every 24 hours
An internal body clocks (EP)
What is the SCN (suprachiasmatic nucleus)?
What is it aka?
What is it a part of?
What happens when it detects light?
The EP for the sleep wake cycle
Aka the master clock
Part of the hypothalamus within the limbic system
When light is detected by the SCN, it sends light to the pineal gland, stopping production of melatonin
What is the circadian sleep wake cycle EP is thought to be?
How did Siffre test this?
Free running, maintaing a predictable cycle without constant entertainment by EZ
Spent 6 months in a cave, with no natural light or other potential EZs
His body clock (EP) maintained a regular cycle of around 25 hours without EZs, longer than the expected 24 hour cycle
What does Siffre’s case study suggest?
Critisism of this study?
The EP for the sleep wake cycle is free running, but needs entertainment to keep to the 24 hour night cycle
- articial lights disrupted measurements of free-running circadian rhythm, acting as an EZ, another study found that the circadian rhythm was closer to 24 hours without the artifical light
How is Vetter’s study evidence that light is EZ?
27 office workers were exposed to strong blue light>would shift their circadian rhythms to match the office lighting
Control group of 27 office workers with normal office lighting rhythm’s matched the shifting time of the natural light of dawn
How is Vetter’s study suggest?
Strongly suggests both light is an EZ and artificial lights can disrupt the EP by over-riding natural light as the primary EZ
How is Ralph’s study evidence that the SCN is an EP?
Golden hamsters with the Tau mutation have a circadian rhythm of 20 hours, compared with 24 hours for normal golden hamsters
When the SCN from normal hamsters was transplanted into the brain of Tau’s, these hamsters gained a sleep wake cycle of 24 hours
Normal hamsters gained a 20 hour cycle when given the SCN from TAU’s
What does Ralph’s study suggest?
SCN is the main EP in the sleep wake cycle
Strength of circadian rhythm
Sleep pattern disruption>anxiety, decreased alertness
A psychological understanding>solutions to the negative effects of jet lag and shift work, ^ economy
Understanding the circadian blood pressure rhythm helps with timing drug and health treatments
Whats an alternative explanation/weakness to the sleep and wake cycle?
Evolutionary explanation- we are not specialized for night time activities
We have a sleep period at night to protect us from accidental harm and predators
This is ignored
