Psy137Homeostasis Hunger

Leptin switches from carb(glucose to fat

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Unformatted text preview: Leptin switches from carb (glucose) to fat usage (lipolysis). Aided by catecholamines (CAT) via Sympathetic NS and T3 Leptin acts via a Gs receptor which via AC/cAMP/PKA prodution phosphorylates hormone sensitive lipase to start lipolysis (I.e burn fat) Long-Term Regulation of Body Weight & Feeding Body weight is generally stable around a “Set Point” but will change with long-term changes in feeding; primarily due to changes in adipose tissue. Regulation & Fat Regulation & Fat Hormones & Fat Hormones & Satiety Hormones & Satiety Figure 9.24 Neuroanatomical model Leptin affects Steroid hormone release via activation of GnRH neurons Fig. 1. Model for the dual roles of leptin in the regulation of adipose mass and reproduction. Leptin is secreted from adipocytes and finds its way to the arcuate region of the hypothalamus where it activates leptin-receptor-expressing neurons. Projections from these neurons will in turn stimulate melanocortin MC4 receptors and neuropeptide Y (NPY)-containing neurons to activate the sympathetic nervous system, which controls lipolysis in white adipose tissue. The firing of gonadotrophin releasing hormone (GnRH)-containing neurons and secretion of GnRH to the pituitary is elicited by leptin-mediated activation of leptin-receptor-expressing neurons and by other factors, such as growth hormone (GH), NPY, insulin and others that control the reproductive axis. The ultimate consequences of leptin activation are the regulation of lipolysis and the firing of the reproductive system. This oversimplification does not show the projections of other neurons, which might impact on either pathway stimulated by leptin. Abbreviations: FSH, follicle-stimulating hormone ; LH, luteinizing hormone. Brain Areas Hunger is associated with increases in rCBF in the hypothalamus, anterior cingulate cortex (ACC), insula, hippocampus Satiety is associated with increases in rCBF in the ventromedial prefrontal cortex (VMPFC), dorsolateral prefrontal cortex (DLPFC), & inferior parietal cortex Fig. 1. Effect of calorie content (HiCal–LoCal). A: Transversal view of significantly active brain areas ( p (FDR) < .05) for HiCal vs. LoCal overlaid on a canonical T1-weighted image. The percent signal change is displayed in the bar plots for each of the significantly active areas. Because these areas showed bilateral activation the results are only shown for one hemisphere. B: Activity in the right orbitofrontal cortex. C: Activity in the left insular cortex. D: Activity in the occipital lobe. Note the different scaling factors for graph 2D. (HM = hungry men, HW = hungry women, NHM = not hungry men, NHW = not hungry women, HiCal = high-caloric and LoCal = low-caloric). The bar plots represent mean percent signal change ± S.E.M....
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Leptin switches from carb(glucose to fat usage(lipolysis...

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