Endogenous Pacemaker Flashcards
Endogenous pacemaker
Internal body clocks that keep biological processes to time
Circadian rhythm
Biological rhythm that lasts around 24 hours
Examples of circadian rhythm
Sleep wake cycle, hormone release etc
Scn
Endogenous pacemaker for sleep wake cycle, known as the master clock.
Part of hypothalamus, when light is detected it sends to the pineal gland which stops melatonin, a hormone that results in a sleep response
What is the role of endogenous pacemakers
To set the free running internal rhythms. It is an internal biological clock that allows organisms to control their internal rhythms and Antocipate cyclical events.
Scn and pineal gland
Scn is made up of neurons locates in hypothalamus, the scn gets info from light(exogenous zeitgeiber) from the eyes. Morning light activates the scn, which signals she pineal gland to decrease melatonin.
The scn keeps the circadian rhythm in synchrony with the external world
Research support for the role of scn MORGAN 1995
Found that I’d the scn of a hamster is removed, then their circadian rhythms will disappear completely. Furthermore, they can be reestablished by transplanting scn cells from foetal hamsters
Suggests the sleep wake cycle is controlled mainly by biological factors
Evidence against Morgan 1995
He used hamsters so findings may not be extrapolated and generalised for humans
Also unethical
Circadian rhythm ao1
Driven by our body clicks and synchronised by the master circadian pacemaker the scn.
Essay first ao1 point
Endogenous pacemaker definition
Circadian rhythm definition
Examples of circadian rhythm
Essay first ao3 point SIFFRE
Siffre- wanted to investigate the role of ep in controlling circadian rhythms.
Isolated himself in cave to see without internal or external factors dictated the circadian rhythm
Biological rhythm would run just over 24 hours
Provides evidence for ep but ez is also necessary
Essay first ao3 extra eval ASCHOFF AND WEAVER
Placed participants in underground bunker with no internal or external cues and the circadian rhythm ran to around 24 hours
Stephen and sucker: investigated role of scn
Rats who had damage to their scn, non existent normal circadian activity
Essay second ao1 point
Scn definition and function
Essay second ao3 point MORGAN
If the scn of hamster was removed then their circadian rhythms will disappear completely. Furthermore, it was found that the rhythms could be reestablished by transplanting scn cells from foetal hamsters
This provides evidence that the biological rhythms is controlled mainly by internal factors
Essay ao3 extra eval MORGAN
Objective scientific data
Difficult to extrapolate
Unethical
