Unformatted text preview: Neurohypophyseal hormone actions AVP = arginine vasopressin (AVP) = ADH produced primarily by neurons of the hypothalamic supraoptic nuclei sent to Posterior Pituitary Increases water permeability of late distal tubules/collecting ducts Direct vasoconstrictor effect: increase blood pressure & HR: V1 & V2 receptors Central osmoreceptors detect excessive osmolarity, stimulating release Oxytocin (OT) Produced primarily by neurons of the hypothalamic paraventricular nucleus Milk ejection reflex (suckling stimulates afferents from the nipples spinal cord (suckling hypothalamus OT release ; IV OT causes milk letdown; neural conditioning of babies' cry can initiate reflex (humans) Cervical dilation (entry into birth canal); sexual excitement & orgasm in males and females (Ferguson reflex-contraction of the vagina during stimulation) Uterine contractions (labor, decreased bleeding, and fetal nonstress testing used as fetal well-being diagnostic) Anterior pituitary hormones: GH GH GROWTH HORMONE Single chain peptide homologous in structure to PRL (Prolactin) Direct GH effects cell glucose uptake (diabetogenic) lipolysis lean muscle mass & protein synthesis* ILGF's (Insulin-Like Growth Factor) *Indirect (ILGF) effects Chondrocyte protein synthesis (I.e. pubertal linear growth spurt-augments early estrogen effects at puberty) lean muscle mass & protein synthesis protein synthesis and organ size of most organs GH deficiency and excess Deficiency disease: failure to grow--short stature, delayed puberty grow--short cause: lack of AP GH secretion or hypothalamic GHRH (GH Releasing Hormone), or GH receptor deficiency Excess disease: excess growth--gigantism (before puberty) growth--gigantism After puberty (acromegaly)-excess periosteal bone growth, organ size, and glucose intolerance Tx: octreotide- somatostatin The endocrine pancreas: Islets of Langerhans Endocrine cells: cells: at outer rim of islets cells: Produce glucagon cells: central cells of islets cells: Produce insulin cells: intermixed cells cells: Somatostatin & gastrin producing Other islet cells secrete... Pancreatic peptide (F cells), VIP... Rapid communications between cells: 1. Gap junctions make - , - , & - cell connections 2. cell blood effluent bathes & cells Glucagon (catabolic, 29 AA like VIP, secretin, GIP) blood glucose is the 1 stimulus for glucagon release (Receptor uses cAMP 2nd messenger at endorgans): Liver: glycogenolysis glucose storage gluconeogenesis* free glucose (by fructose 2, 6 bisphosphate & phosphofructokinase enzyme activity) Fat: circulating fatty and keto-acids (acetoacetate, -OH-butyrate from acetyl CoA of TCA cycle) lipolysis ( shunt to TCA cycle energy generation synthesis) ( *protein deamination to make glucose (excreting more urea) INSULIN (I): & chains joined by 2 disulfide bridges Proinsulin + C-peptide removal e. g. Assay C-peptide to monitor I release active insulin (I) glucose is major stimulus, others also glycemic hormones 2 arily stimulate I release by glucose levels also Sequence of events: glucose binds to Glut 2 receptor cell uptake in proportion to blood levels (Facil. diffusion) ATP* synthesis K+ efflux channels close open Ca2+ channels [Ca2+] synthesis channels cell depolarization I exocytotic secretion I circulates in blood I binds to tyrosine kinase blood receptor ( & subunits) in target tissue subunits autophophorylate, etc. ...effects tissue Meanwhile, the I-R complex internalizes, down-regulating target cells to I; e. g. I receptors Meanwhile, in starvation & in obesity ...
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- Spring '08
- Physiology, blood glucose, intermixed cells cells, GH GH GROWTH