biological rhythms: circadian rhythms Flashcards
what are biological rhythms
distinct patterns of changes in body activity that conforms to cyclical time periods
Biological rhythms are influenced by internal body clocks (endogenous pacemakers) as well as external changes to the environment (exogenous zeitgebers)
What is a circadian rhythm
They ate biological rhymes, subject to a 24 hour cycle, which regulates a number of body processes such as the sleep wake cycle and changes to core body temperature
What are biological rhythms governed by
They are governed by two things:
Endogenous pacemakers
Exogenous zeitgebers
What are enogenous pacemakers
These are the body’s internal biological clock
What are exogenous zeitgebers
These are external changes in the environment
What are ultradian rhythms
These are rhythms that pccur many times during the day
What is an infradian rhythm
These are rhythms that take longer than a day to complete (circannual rhythm)
What are two examples of a circadian rhythm
The sleep wake cycle
Body temperature
What exogenous zeitgeber governs the sleep wake cycle
Daylight is a powerful exogenous zeitgeber hence why we feel drowsy at night time an alert during the day.
This exogenous zeitgeber is incredible important in the sleep wake cycle
What is the endogenous pacemakers that governs that sleep wake cycle
The sleep cycle is also governed by internal endogenous pacemaker called the suprachiasmatic nucleus (SCN)
It acts a biological clock. It can be reset by exogenous zeitgebers
Where is the SCN
It lies just above the optic chasm which provides information from the eye about light
What happens if the SCN was let to its own devices
This is referred to as free running
Essentially there is no external stimuli such a light and we have no idea whether it was night or day
The question would be: would we still falk asleep and wake regulae times
The researcher Michael Siffre looked into this
What is the Siffre’s cave study
He spent several periods underground to study the effects on his own biological rhythms
He was deprived od exposure to natural light and sound, but with access to adequate food and drink.
Siffe resurfaced in midsurfced in mid September 1962 after 2 months jn the caves of the Douthern Alps believing it to be mid August
A decade later her performed a similar feat for six months in a Texan cave
In each case his free running biological rhythm settles to one just beyond the usual 24 hours though he did continue to fall asleep an wake on a regular schedule
