18 12 p 679 fig 18 11 p 677 hipwwwanatomyatlasesorg

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Unformatted text preview: from again? •  And how are those hormones regulated? •  And where are the regulators released from? –  growth hormone–releasing hormone (GHRH) –  growth hormone–inhibi=ng hormone (GHIH or somatosta=n) Major inputs Blood amino acids, Blood fatty acids Exercise, stress, blood glucose Ghrelin Diurnal rhythm Minor inputs Hypothalamus Somatostatin (growth hormone–inhibiting hormone; GHIH) Growth hormone– releasing hormone (GHRH) Anterior pituitary somatotrope Growth hormone Liver IGF-I Growth-promoting actions cell division protein synthesis ( blood amino acids) bone growth Metabolic actions unrelated to growth fat breakdown (blood fatty acids) glucose uptake by muscles (blood glucose) glucose output by liver (blood glucose) Fig. 18-10, p. 676 GH Dysregula=on: Timing MaIers Gigan4sm •  Caused by excess GH secre=on during childhood •  Epiphyseal plate is s=ll present in long bones •  Long bones are s=ll able to grow longer Acromegaly •  Caused by excess GH secre=on during adulthood •  Long bones are not able to elongate because epiphyses have fused •  All bones grow thicker, soX =ssues proliferate Gigan4sm Acromegaly Fig. 18- 12, p. 679 Fig. 18- 11, p. 677 hIp://www.anatomyatlases.org/ Circadian Rhythms •  Like many hormones, GH secre=on displays a diurnal rhythm –  How does the hypothalamus “know” what =me it is? •  The suprachiasma4c nucleus (SCN) of the hypothalamus is the body’s biological clock. –  Slow changes in the concentra=on of clock proteins in the SCN cause 24h- ish cycles of neural ac=vity –  Specialized ganglion cells from the re4na project directly to the SCN, causing photentrainment: sebng the clock to match light/dark cycles at 24h exactly Photoentrainment and “free run”...
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