Endocrine Pancreas Flashcards
What are the four types of cells in the Islets of Langerhans and what do they secrete
alpha cells: glucagon
beta cells: insulin
delta cells: somatostatin
F cells: pancreatic polypeptide
What are the effects of ANS innervation of the pancreas
sympathetic: stimulates glucagon release and inhibits insulin release
parasympathetic: stimulates release of both insulin and glucagon n
What are the three methods by which the cells of the islets communicate
gap junctions
unique nature of blood supply
innervation
How are the islets vascularized
arteriole enters at the center of the islet
spread out a network of fenestrated capillaries
then converge into venules at the edge
How is there internal innervation in the islets
delta cells send dendritic like processes onto beta cells to aid in coordination and communication
How many disulfide bridges are there in insulin? how many are within the alpha chain and how many link the alpha and beta chain together
there are 3 disulfide bridges and one is within the alpha chain, the other two link the alpha and beta chain
describe the synthesis of insulin
1.translation of mRNA yields preproinsulin
2.signal peptide is cleaved yielding proinsulin
3.proinsulin is shuttled to ER and folded with the bridges
4.proinsulin is packaged into secretory granules in Golgi
5. inside the granules, proteases cleave the c peptide yielding insulin
If a patient is receiving exogenous insulin how could you measure their endogenous levels
by measuring the c-peptide in their plasma
Briefly describe glucose mediated insulin secretion
1.glucose enters B cell via GLUT2 transporter
2.Glucose is phosphorylated to G6P
3.G6P is oxidized to ATP
4. ATP closes ATP sensitive K channels
5. increasing K levels depolarize beta cells
6.depolarization opens voltage gated Ca2+ channels
7.Ca2+ concentration inside cell increases
8. increased Ca2+ concentration causes exocytosis of insulin containing granules
True/False: oral glucose is a more powerful stimulant for insulin secretion than intraveous
true
What two hormones are released from enteroendocrine cells in response to oral glucose
GIP and GLP-1
What are the effect of GIP and GLP-1 on insulin levels
stimulatory
True/False: GI AAs, fatty acids, ketoacids directly stimulate release of insulin
false, they indirectly stimulate via incretins
How does exercise inhibit insulin secretion
by stimulating alpha 1 andrenergic receptors on beta cells
True/False: insulin also binds to elements in the nucleus, golgi, and ER to influence gene transcription
true
Describe how insulin decreases blood glucose levels
-increases number of GLUT4 transporters in cell membranes
-promotes formation of glycogen in liver and muscle while inhibiting glycogenolysis
-inhibits gluconeogenesis
Describe how insulin decreases blood fatty acid concentration
-stimulates storage of fatty acids in adipose
-inhibits lipolysis
Describe how insulin decreases blood amino acid concentration
increases amino acid and protein uptake by tissues by activating transport systems in cell membranes
What is insulins effect on blood K+ concentrations
-it promotes K+ uptake into the cells by increasing Na/K ATPase activity
-has a direct effect on the hypothalamic satiety center
True/False: insulin has direct effect on the hypothalamic satiety center dependent on change in blood glucose levels
False, this action is independent of changes in blood glucose
What organ is the primary target of glucagon
the liver because it stimulates hepatic glycogenolysis and gluconeogenesis
