condense ntoes on readings for lecture 5

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Department
Psychology
Course
PSYC 388
Professor
Ralph Mistlberger
Semester
Summer

Description
Chapter 5 search for the clock - motivation = dominant model range of homeostatic drives or motivations that determined behaviour, so if animal became increasingly hungry and at set point it would feed and if filled calories reservoir the hunger drive would diminish and replaced by another such as thirst drive = rotating repertories of drives and their concomitant behaviours, each drive take turn at top of hierarchy problem = why particular drives regularly appeared at certain times of day = answer = nocturnal animal active at night so uses up more energy during night than day so all physiological parameters are higher at night because adaptive and success and controlled by a clock - homeostatic mechanism takes care of environmental fluctuations (ex. Humidity),but its a fine turner rather than main controller - hypothalamus regulate blood pressure body temperature, fluid and electrolyte balance, metabolism of fats and carbohydrates and sugar levels, timing of release of hormones (egg) - lesions in front part of hypothalamus eliminated motile behaviour rhythms - hypothalamus and thalamus work together to generate sleepwake cycle - release of hormones linked to arousal sate of animals and coordination needed to bring it into line = circadian oscillator - suprachiasmatic nuclei (SCN) =lesion = abolished oestrous cycle and rhythms in behaviour such as drinking and locomotion - Moores approach = follow light beam as it came through eye and see where it went (known pathway that took light to optic nerve to visual processing ; optic nerves cut before optic chiasm then LD cycles no longer entrained biological clock; but cut just after optic chiasm LD cycle entrainment unaffected) = suggested distinct pathway separate form visual projection responsible for transmitting signals for setting clock ~ injected radioactive amino acid into eyes and follow tracer molecules ~ New pathway from eye to SCN = retinohypothalamic tract ~ scn lesion = loss of circadian rhythm of hormone corticosterone, involved in circadian timing of neurosecretion ~ Remove whole SCN destroyed behavioural and endocrine circadian rhythms - SCN in mammals was clock that regulated several functions with period of ~24hours - Mid 1970s well established destroying SCN affected timing of various behaviours in mammals but didnt abolish behaviours themselves = arrhythmic - SCN isolated (hard because cells locate very close t several major nuclei and tracts) within animal experiment = pattern continued with in SCN itself but rhythmicity abolished in nearby neurones outside cut suggest endogenous rhythm produced with in SCN an electrical signals carried by neural connections leading away from it (efferents) provided timing information to other brain regions - SCN neurones within SCN generate circadian rhythm of electrical activity high in day and low at night; neurones outside SCN showed circadian rhythmcity but out of phase =peaked in night and lowest during day - SCN dissected = generates stable rhythm with period of ~ 24 hours and self-sustaining oscillator - Schwartz found SCN metabolically active during light phase of 12 hours light12 hours dark cycle and relatively inactive during dark phase = rhythm = rhythm of glucose utilisation is circadian (evidence) + direct effect when restored circadian activity rhythms in SCNM-lesion rats and hamsters by transplant foetal SCN (no transplant = discernible pattern of sleep and wake, but regained activity rhythms when received transplant) + mutant golden hamster - Radioactive 2 deoxyglucose (2DG) = similar to glucose = insert in vein= slice brain the place on x-ray films = developed films clearly show location of radioacivley labelled 2DG and intensity of image indicated by amounts of moelculte present in tissue eof slice - Simple model of mammalian circadian organisation circadian clock in SCN produces rhythmic output that drives circadian rhythms of activity: drinking, feed, sleep, etc. The oscillator rhythm locked on to local time by daily entrainment of dawn, duskboth model show one master clock controlling all rhythmic activity - Neural projections from SCN = main ones are to areas in hypothalamus, thalamus and midbrain; neurones in scn send direct and indirect projections to neurosecretory CRF neurones in hypothalamus = corti
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