Circadium Rhythms Flashcards
What are biological rhythms?
Period activity controlled by endogenous pacemakers and exogenous zeitgebers
What is an endogenous pacemaker?
Internal biological ‘clocks’ which govern biological rhythms.
What are exogenous zeitgebers?
External changes in the environment which govern biological rhythms.
What is a circadian rhythm?
A biological rhythm which lasts for 24 hours.
Give an example of a circadian rhythm?
The sleep / wake cycle.
Outline the endogenous pacemaker involved in the circadian rhythm: the sleep / wake cycle.
A biological clock without the influence of external stimuli eg light.
Outline the exogenous zeitgeber involved in the circadian rhythm: the sleep / wake cycle.
The fact we feel drowsy when it’s night time and alert during RH day shows the effects of daylight.
In what way can the exogenous zeitgebers influence the sleep / wake cycle?
The exogenous zeitgeber (light) can resent the SCN.
What is the importance of the SCN in the sleep / wake cycle?
The SCN receives info about light direct from the optic chiasm (this is just below the SCN).
Say what the research is into circadian rhythms?
Suffer spent long periods in darks caves.
Over a 2 month and then 6 month period, his free running circadian rhythm settled to 25 hours. And had a regular sleep / wake cycle.
Which has a stronger influence: endogenous pacemakers or exogenous zeitgebers?
Endogenous pacemaker
In what way do endogenous pacemakers have a greater influence over circadian rhythms than exogenous zeitgebers?
- Folkard et al studied 12 people who lived in a dark cave for 3 weeks, going to bed at 11:45 and waking up at 7:45.
- the researchers gradually sped up the clock (unbeknown to pps) so an apparent 24 hour day eventually lasted 22 hours.
- only one pp comfortably adjusted to the new regime. Suggesting that the existence of a strong free-running circadian rhythm cannot easily be overridden by changes in the external environment.
