Endogenous Pacemakers & Exogenous Zeitgebers Essay Plan

Discuss the effect of endogenous pacemakers and exogenous zeitgebers on the sleep/wake cycle - 16 marks 

AO1 - (6 marks)

ENDOGENOUS PACEMAKERS AND SLEEP/WAKE CYCLE

- Suprachiasmatic nucleus in hypothamalmus influential in maintaining circadian rhythms. Receives info about light from optic chiasm and this continues when eyes closed which enables biological clock to adjust to changing patterns of daylight during sleep

- SCN gives info on daylight and length to pineal galnd that increases melatonin at night to induce sleep

- DeCoursey destroyed SCN connections in 30 chipmunks and observed in natural habitat for 80 days. Found s/w cycle gone and significant amount dead from predators. Emphasises role of SCN in maintaining circadian s/w cycle. 

EXOGENOUS ZEITGEBERS AND SLEEP/WAKE CYCLE 

- External factors that reset biological clocks through process of entrainment

- Light can reset SCN and so plays role in maintaining s/w cycle. Light has indirect influence of body processes that control functions e.g hormone secretion. 

- Light investiated by Campbell and…