Lesson 13 - Endogenous Pacemakers and Exogenous Zeitgebers Flashcards
What is an example of an Endogenous Pacemakers ?
The suprechiasmatic nuclei (SCN). The SCN is a tiny cluster of nerve cells in the hypothalamus. It acts as the body’s master clock
How does the SCN work ?
Neurone within the SCN synchronise with each other, so their target neurone in sites elsewhere in the body receive time-coordinated signals. The SCN is reseted by a change in external light
What is a strength of Endogenous pacemakers ?
Folkard studied a uni student who spent 25 days in a lab with no access to the stimuli of light to reset the SCN. However after 25 days core temp rhythm was still 24 hours. This study therefore shows the importance of endogenous pacemakers
What is a weakness of endogenous pacemakers ?
The uni students sleep cycle extended to 30 hours with periods of sleep up to 16 hours. Suggests we need exogenous zeitgebers more than endogenous pacemakers
What is an Exogenous Zeitgebers?
Environmental events thet are responsible for painting the biological clock of an organism
How does the SCN use exogenous zeitgebars?
Receptors in SCN are sensitive to changes in light levels during the day and use this information to synchronise the activity of the body organs and glands.
What is a strength of Exogenous Zeitgebers ?
Vast majority of blind people with light perception have normal circadian rhythms. Blind people without light perception show abnormal circadian rhythms.
What is a weakness of Exogenous Zeitgebers ?
Studies of individuals in arctic where sun doesn’t set in Summer shows normal sleeping patterns suggesting there are occasions where the exogenous zeitegeber of light has little bearing on biological rhythm.
