Endogenous pacemaker='biological clock' Exogenous zeitgebers=external cues: light, social etc.
Interaction of proteins that regulate the biological clock of a fruit fly in a cycle (DARLINGTON): Morning- 2 proteins CLOCK & CYCLE bind -->prompts prod. PER & TIM --> PER & TIM render CLOCK & CYCLE inactive (as PER & TIM increase CLK & CYC decrease) --> as CLK & CYC decrease prod. of PER & TIM decreases (negative feedback) --> cycle starts again.. morning LIGHT prompting prod. CLK &CYC --> cycle takes 24 hours
High reliability b/c biological evidence provides objective, scientific evidence --> replicated many times.. different species, various forms--> H/W reductionist view: ignores most other factors .. looks at proteins in isolation --> basis of system 2 identifiable proteins (reductionist appropriate) but importance of light should be taken into account
Main endogenous pacemaker: Superchiasmatic Nucleus (SCN) in hypothalamus --> info. from light (optic nerve even eye shut) --> SCN responds to light levels & resets sleep wake cycle ... morning light wake up --> directs pineal gland: produces melatonin at night prompt us sleep
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