Bio Rhythms: Infradian & Ultradian Rhythms Flashcards
What are endogenous pacemakers?
Internal body clocks that regulate many of our biological rhythms, such as the influence of the suprachriasmatic nucleus on the sleep/wake cycle.
What is the suprachriasmatic nucleus?
A tiny bundle of nerve cells located in the hypothalamus in each hemisphere of the brain, it is one of the primary endogenous pacemakers in mammalian species.
Where is the suprachriasmatic nucleus and what does it do?
The SCN lies just above the optic chiasm and receives information about the light directly from this structure, this continues even when eyes are closed enabling the biological clock to adjust to changing patterns of daylight whilst we are asleep.
What have animal studies showing about the SCN?
Decoursey et al. (2000) destroyed the SCN connections in the brains of 30 chipmunks – they were returned to the wild and observed for eighty days – the sleep wake cycle of the chipmunks disappeared – a large proportion of them were killed likely because they were awake and vulnerable when they should’ve been asleep.
What does the pineal gland do and where is it?
It is a pea like structure in the brain just behind the hypothalamus, it receives information from the SCN and during night it increases production of melatonin a chemical that induces sleep and is inhibited during periods of wakefulness.
What are exogenous zeitgebers?
External cues that may affect or entrain our biological rhythms, such as the influence of light on the sleep/wake cycle.
What do exogenous zeitgebers do?
They reset our biological clocks through a process known as entrainment – it seems sleeping and wakefulness are determined by an interaction of internal and external factors.
Give two examples of exogenous zeitgebers?
Light and social cues .
How is light an exogenous zeitgeber?
It can reset the bodies main indigenous pacemaker, the SCN, so helps maintain the sleep/wake cycle it also indirectly influence hormone secretion and blood circulation.
What study did Scott Campbell and Patricia Murphy (1998) do into light?
They demonstrated that the light may be detected by skin receptors sites on the body even when the same information is not received by the eyes. 15 participants were woken on various times in the night with light shone on the back of their knees. The researchers found the sleep wake cycle varied by as much as three hours showing how light is a powerful endogenous zeitgeber
How are social cues an exogenous zeitgeber?
The schedules imposed by parents are likely to be influential in maintaining circadian rhythm also meal times and bed times will have an effect, research suggests that adapting to local time for eating and sleeping is an affective way of entraining circadian rhythm and beating jetlag when travelling long distances.
How does the sleep/wake cycle develop from infancy?
The initial sleep/wake cycle is pretty much random, at about six weeks circadian rhythm begin and at about 16 weeks babies are entrained.
What is a problem with the SCN as an influencer of the sleep/wake cycle? (Eval -)
Research has revealed there are numerous circadian rhythm in many organs and cells of the body, these are called peripheral oscillators and are found in the lungs, liver, pancreas and more. These clocks are highly influenced by the SCN but they can act independently this suggests that there may be other complex influences on the sleep/wake cycle.
What are the potential problems with the use of animal studies for investigating the sleep/wake cycle?
There may be ethical issues involved in some animals studies – some animals were exposed to considerable harm and subsequent risk – the chipmunks - can we justify this?
What methodological issues have caused problems in research? (Eval –)
Findings from the Campbell and Murphy study are yet to be replicated and some psychologists believe there may have been a confounding variable with some limited light being exposed to the participants eyes this reduces the validity/reliability of the results.
