17. Endogenous Pacemakers And Exogenous Zeitgebers AO1 Flashcards
What is the SCN
The suprachiasmatic nucleus
What is the suprachiasmatic nucleus
A primary endogenous pacemaker
Explain what an SCN is
A tiny bundle of nerve cells in the hypothalamus which helps maintain circadian rhythms
Where is the SCN located
Lies just above the optic chiasm and receives information about light
What did DeCoursy et al study?
Destroyed SCN connections in the brains of 30 chipmunks which were returned to their natural habitat and observed for 80 days
What did DeCoursy et al find?
Their sleep/wake cycles disappeared and many were killed by predators
Give two examples of endogenous mechanisms
Pineal glands and melatonin
What does the SCN do?
Passes information on day length to the pineal gland which increases production of melatonin during the night
What is melatonin
A hormone that induces sleep and is inhibited during periods of wakefulness
What are exogenous zeitgebers
External environmental factors that reset biological clocks
What happens without external cues?
The free running biological clock continues to take in a cyclical pattern
What do zeitgebers do?
Reset the sleep/wake cycle, and interaction of internal and external factors
What is a key exogenous zeitgeber and what does it do
Light - influences the sleep/wake cycle
What can light do
Reset the bodies main endogenous pacemaker, and have an indirect influence on key processes in the body controlling hormone secretion, blood circulation…
What did Campbell and Murphy study?
Woke 15 participants at various times and shone the light on the back of the knees, producing a deviation in the sleep/wake cycle of up to 3 hours
What was found about light?
Light is a powerful exogenous zeitgeber detected by skin receptor sites and does not necessarily rely on the eyes to influence the DCN
Describe newborns sleep/wake cycle
Fairly random in newborns but most babies are entrained by about six weeks
What entrails babies?
Schedules imposed by parents or a key influence including adult determined meal times and bed times
What does research show about adapting times?
People adapt to local times for eating and sleeping (not responding to one’s own feelings of hunger and fatigue) tackles jetlag
