PHYSL402 Lecture Notes - Lecture 2: Signal Transduction, Hydrolysis, Pancreatic Polypeptide
13 Oct 2016
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Document Summary
Both hormones secreted by endocrine cells of pancreas. Short half-lives require continuous secretion insulin glucagon. Low blood glucose = evolutionarily bad (prevent survival/reproduce) Hourly regulation of metabolism dependent on: insulin and glucagon. Alpha cell = glucagon (25% of islet cells) D cells = somatostatin (~10% of islet cells) inhibits both glucagon and insulin. Pp cells (f cells): pancreatic polypeptide (role not well known) Extensive capillary network supplies islets reduced capillary network in diabetics (rarefaction) Loss of beta cells (chicken and egg problem) <2% of total organ mass (low % = interesting) Islets of langerhans: small cell clusters throughout pancreas. Islets contain 4 cell types: each = assoc with secretion of 1 or more peptide hormones. Close islet cell relationship direct control of hormone secretion by other hormones. W/o reg of enzymatic activity, pathway will simply cycle back and forth. Ps and s neurons terminate directly on islets. Nervous system influences metabolism (prob not to extent of endocrine)
