Endogenous pacemakers and zeitgebers Flashcards
What are endogenous pacemakers?
Innate mechanism that sets timing of biological rhythms and acts as the internal body clock
How is the sleep cycle regulated?
The suprachiasmatic nucleus (SCN)
What are exogenous zeitgebers?
Environmental factors reset our internal clock
What are examples of exogenous zeitgebers?
Entrainment, light and social cues
How is entrainment an exogenous zeitgeber?
It is an external factor that actually changes our internal body clock
How is light an exogenous zeitgeber?
It directly affects the SCN
How are social cues an exogenous zeitgeber?
Mealtimes and bedtimes can ‘entrain’ our bodies to differ sleep/wake cycles
How is the sleep cycle regulated by the SCN?
- Low light
- Opioid chiasm behind eye
- Stimulates SCN
- Stimulates the pineal gland
- Produces melatonin
- Affects production of serotonin
- Brain activity falls
- Sleep
What is research evidence for the role of the SCN?
Decoursey and Ralph
What was Decoursey’s research?
The SCN was removed from chipmunks and many of them died, showing evidence for how the SCN controls sleep/wake cycle as chipmunks died due to being awake at the wrong time - shows effects of sleep/wake cycle on survival
What was Ralph’s research?
SCN cells of mutant hamsters with a 20h sleep/wake cycle were implanted into normal hamsters and their sleep/wake cycle became 20h, showing evidence for how SCN effects sleep/wake cycle
What is research for the importance of zeitgebers?
Campbell and Murphy
What was Campbell and Murphy’s research?
They shone a light on the back of particpants knees which effected their sleep/wake cycle, showing the impact of light on the sleep/wake cycle not just for eyes
How may circadian rhythms be present at other levels?
The may work at a cellular level so individual cells and organs can display circadian rhythms
What does Campbell and Murphys’s research show evidence for zeitgebers?
Light is a powerful zeitgeber and can alter sleep.wake cycle even without effecting SCN
