Biological Rhythms Notes

HideShow resource information
Preview of Biological Rhythms Notes

First 568 words of the document:

Biological Rhythms & Sleep
Humans, in general, get up in the morning and go to bed at night. We tend to stick to this pattern
even when we have the opportunity to change our behaviour, for instance, on holiday. We also see
difficulties in sleeping if we break our usual cycle, for instance, travelling abroad by air. Animals,
including humans are controlled by a regular cycle of bodily changes. This can be endogenous
(internally controlled) or exogenous (externally controlled)
Biological rhythms help animals to measure time, enabling them to anticipate changes and
respond in advance of seeing them and to synchronise behaviours. (example; a bee will know when
to go to a patch of flowers that only open at night, and female moths can release pheromones at
different times to other species of moth to avoid confusion when trying to attract a mate.)
Types of Biological Rhythms;
Circadian Rhythms ­ bodily cycles that occur every 24 hours (example; sleep/wake cycle)
Ultradian Rhythms ­ bodily cycles that occur several times a day (example; cycles of sleep)
Infradian Rhythms ­ bodily cycles that occur less than once a day (example; menstrual
Circannual Rhythms - bodily cycles that are repeated yearly
The sleep/wake cycle is an example of a circadian rhythm. We can `lie in' however; we cannot sleep
indefinitely or go completely without sleep. Along with this, we also have a rhythmical variation in
awareness. Our cognitive processing drops when our body clock expects us to be asleep. Other
functions are also affected, these include; sensitivity to pain, manual dexterity and reaction time,
as well as behaviours like eating and drinking (tend to eat less, as energy is required to digest food)
our emotions (more emotional) and physiological processes (for example; the metabolism of
alcohol is slower, therefore you get drunk quicker and may react differently)
Folkard (1996) reported the case of Kate Aldcroft, a university student, who was placed in a lab for
25 days with no information about the time of day. She was asked to play her bagpipes twice a
day at what she believe was the same time. She began to sleep for longer (up to 16 hours at a
time) and her sleep/wake cycle extended to 30 hours. This suggests a strong role for exogenous
cues, as the normal sleep/wake cycle is 24 hours. However, there are also endogenous factors
(pacemaker) present as a cycle still remained. This is a case study of a university student, therefore
there are problems with generalisabiliy as the findings may not be representative of the whole
population. The study was also conducted in a lab, this was necessary for controls, however it
means that there was a lack of mundane realism and therefore real-life behaviour may not be
Groblewski et al (1980) supported the spontaneous lengthening of the circadian cycle, finding that
rats advanced by an hour a day without exposure to daylight .As this research uses animal
research, there are ethical and generalisabiliy concerns, however in this situation it may be
necessary to use animals as they are less complex and confounding variables are eliminated.
Empson (1993) found that humans can keep their body clock in time through daily exposure to

Other pages in this set

Page 2

Preview of page 2

Here's a taster:

research suggests an endogenous clock, but also recognises the important of exogenous factors.
Both internal and external factors appear to be involved in the control of circadian rhythms. The
most obvious zeitgeber (external factor that indicates time) is light, where the levels are detected in
the eyes and passed onto the brain and endocrine system. The retina detects the light level, which
passes it on to the retinal ganglion cells (Provencio et al, 2000).…read more

Page 3

Preview of page 3

Here's a taster:

The SCN is therefore considered an endogenous pacemaker.…read more


No comments have yet been made

Similar Psychology resources:

See all Psychology resources »See all resources »