Endogenous Pacemakers and Exogenous Zeitgebers 0.0 / 5 ? PsychologyBiopsychA2/A-levelAQA Created by: lauraking20Created on: 13-06-17 13:22 2 Endogenous? SCN & Pineal gland 1 of 17 Where is the SCN? Hypothalamus 2 of 17 What ensures that all biological clocks receive correctly timed co-ordinated signals? Spontaneous synchronicity of SCN neurones 3 of 17 What brain regions does it link? Those that control sleep and arousal 4 of 17 Changes in external light? Info about the changes are sent along the optic nerve to the SCN 5 of 17 What does it regulate? The manufacture and secretion of serotonin 6 of 17 What does the pineal gland release? Melatonin 7 of 17 What does this hormone do? Inhibits brain mechanisms that promote wake (therefore increases at night) 8 of 17 2 types of exogenous? Light and social cues 9 of 17 What detects light intensity in the eyes? Photoreceptors 10 of 17 How is the sleep wake cycle maintained in blind ppl? Connections between eye & SNC still present (so still influenced by light) 11 of 17 What do social cues compensate for? A lack of natural zeitgebers (e.g. meal times) 12 of 17 Animal studies Bred hamsters with 20 hr CR, implanted SCN neurones in health hamsters, CR also extended to 20 hrs 13 of 17 Separate rhythms Aldcroft - 25 dears with no access to zeitgebers = core body temp maintained 24 hr cycle / sleep wake increased to 30 hrs 14 of 17 Jet lag Pps exposed to continuous bright light - CR shifted back 2.1 hours = so exposure to bright before tale to decrease readjustment time? 15 of 17 Artificial light Ppl working under normal 'warm' light = synchronisation to natural sunrise on days off / blue enriched light = office hours on free days 16 of 17 Therefore what does this suggest? Light is the dominant zeitgeber 17 of 17
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