Y13 Biopsychology - Biological Rhythms Flashcards
What are circadian rhythms?
They have cycles that generally occur once every 24hrs e.g. the sleep-wake cycle.
What are infradian rhythms?
They have cycles that occur less than once every 24hrs e.g. the menstrual cycle.
What are ultradian rhythms?
They have cycles that occur more than once every 24hrs e.g. the stages of the sleep cycle.
What are endogenous pacemakers?
The body’s internal body/biological clock that regulates biological rhythms.
What are exogenous zeitgebers?
Influences outside the body (external factors) that act like a prompt, which may trigger a biological rhythm (they reset our biological clocks) e.g. light.
What is the SCN?
A part of the hypothalamus which acts a an internal clock to keep the body on an approx. 24hr sleep-waking cycle.
Describe the sleep cycle.
1) Light is detected by the eye and a signal is sent to the SCN via the optic nerve.
2) The SCN will then send a signal to the pineal gland.
3) If there is low light the pineal gland will secrete melatonin but if there is more light the secretion of melatonin will be inhibited.
4) Melatonin is the hormone which makes you tired and encourages sleep.
It terms of the sleep cycle what is light, the SCN and the pineal gland?
Light = exogenous zeitgeber
SCN and pineal gland = endogenous pacemaker
Describe DeCoursey’s study (2000).
- Destroyed the SCN in 30 chipmunks who were then returned to their natural habitat.
- Their sleep-wake cycle disappeared and their sleep became random.
- By the end of the study a significant proportion were killed by predators (presumably because they were awake and vulnerable when they should of been asleep).
Describe Siffre’s study (1962/1975) - double check.
- Spent 61 days and nights in a cave with no exogenous zeitgebers.
- His only influence were endogenous pacemakers.
- When he emerged from the cave he believed it to be 20th August but it was in fact the 17th September.
- His sleep-wake cycle extended from a 24hr cycle to a 25-30hr cycle.
Describe Aschoff et al study (1971).
- Social stimuli, such as mealtimes and social activities, may also have a role as zeitgebers.
- Individuals are able to compensate for the absence of zeitgebers such as natural light by responding to social zeitgebers instead.
Describe Klein and Wegmann’s study (1974).
They found that the circadian rhythms of air travellers adjusted more quickly if they went outside more at their destination. This was thought to be because they were exposed to the social cues of their new time zone, which acted as a zeitgeber.
