endogenous pacemaker

• internal body clock regulate biological rhythms such as the scn on circadian rhythm
• scn:

  cells in the hypothalamus in each hemisphere maintaining circadian rhythm. nerves fibres connected to optic chiasm and receives info about light at night enabling bio clock to adjust to changing patterns of light
• pineal gland and melatonin:

  scn passes the info on day length and light that passes info to pineal gland. during night increase production melatonin chemical which induces sleep inhibited when awake
• decoursey 2000:

  destroyed scn connections in brain of 30 chipmunks returned to natural habitat observed 80 days. sleep wake cycle disappeared majority killed by predators
• ralph 1990:

  bred mutant hamsters 20hr sleep wake cycle. when scn cells from foetal tissue transplanted brain normal hamsters cycle went to 20hrs
• animals studies have been used to support role of scn. decoursey and ralph demonstrates the importance of scn in regulating circadian rhythm. using animal studies allow high degree experimental control as researchers able to control which part of brain/ genes they want to remove . therefore high internal validity . issues generalising to humans as animals simple whereas human complex therefore different behaviour
• total isolation studies e.g siffres cave study rare.made us artificial light to reset bio clock. everyday life endogenous and exogenous interact therefore makes little sense to separate for research. argued that researcher preoccupied separating bio and environmental to study them in isolation to conduct reductionist research to establish causal relationships. focus reductionism misled as both responsible for circadian rhythm. adopt interactionist approach
• Research has revealed that there are many circadian rhythm in many organs. these peripheral oscillators found in organs such as lungs, pancreas, and skins. they're influenced by the actions of the scn but also act independently. damiola 2000 demonstrated how changing feeding patterns in mice alter circadian rhythms of cells in liver by 12 hours while leaving scn rhythm unaffected. argued research heavily focused role on scn in sleep wake cycle at the expense of having an understanding of endogenous pacemakers. research like damiolas practical applications