PSL201Y1 Lecture Notes - Orexin
Document Summary
Circadian modulation: hormone synthesis & secretion fluctuation; ex. But oscillator takes 24hrs anyway so don"t need retinal for 24hr oscillation. Pineal body: melatonin involved in sleep induction, enhances activated via sym system in darkness (cf. pupillary light reflex) secretes melatonin right into bloodstream; blocked by even small amts of light (esp blue-green) target neurons ex. In superchiasmic n. to deeper sleep, not actually necessary but promotes: maximal secretion at about 2 a. m. period of deep sleep, higher secretion in summer (much shorter nights so compensates w more melatonin) than winter. Sleep switch" in ventrolateral preoptic n. of anterior hypothal (beside cooling area): activated by 1) circadian clock, 2) sleep debt (as brain glycogen , or adenosine. (metabolite of atp broken down in extracellular fluid); inhibitory. Waking switch" in tuberomamillary nucleus in posterior hypothal. Histamine activating system: excitatory to brainstem activating systems: 2 centers of hypothal mutually inhibit each other, drive comes from superchiasmatic nucleus.
