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Pancreas as endocrine organ:Glucose homeostasis & Insulin
Nermeen Bastawy
Physiology Department
Faculty of Medicine
Cairo University
F
60% 25 %
Pro insulin
Ribosomes ER /Golgi Golgi/Granules
Mechanism of insulin release• Phases :11stst phase phase: rapid, short, glucose dependent: rapid, short, glucose dependent2nd phase: slow,sustained, glucose independent
• Oscillation pattern:
every 5 min.
Insulin receptors & effects
IRSNa/K ATpase
Glucokinase
Lipase GLUT4
K, aa
Glucose transporters (9(
2ry active transp. Facilitated Diffusion
GROWTH & METABOLISM
• Proteins & growth (anabolic(• CHO : insulin sensitive tissues
( muscle, adipose, liver(• Fat & KB
INSULIN
FFAGlucose
Adipose
ATP
-- lipase
G6P
GK
GSTG & VLDL
lipase
FFA
Adipose
GLUT2
ATP
Lipase
Hs-Lipase
Insulin & K+ ???
• Insulin K shift into the cells by ++ Na/K ATPase. That's why insulin is used in the treatment of hyperkalemia.
• Hyperkalemia: more K will enter beta cell ++ insulin secretion
• Hypokalemia more K will leave beta cell -- insulin secretion.
• Why diuretics are contraindicated in DM?
Control of insulin secretion
• Hypothalamus/pituitary? NOT
• Feed back? Glucose / Insulin
• +++/- - - - ?
FOOD Hs ANS K+ cAMP
70 100 300
Insulin
Glucose mg %
Max
Basal
Control of insulin secretion
• Hypothalamus/pituitary? NOT
• Feed back? GLUCOSE/Insulin
• +++/- - - - ?
FOOD Hs ANS K+ cAMP
How dose food ++ insulin secretion?
W is better stimulant 4 insulin secretion: oral or IV glucose?
Control of insulin secretion
• Hypothalamus/pituitary? NOT
• Feed back? GLUCOSE/Insulin
• +++/- - - - ?
FOOD Hs ANS K+ cAMP
Glucagon
• Pancreas (A cells)
• GIT & brain ( A & L cells)
• Actions:
1. Oppose insulin
2. ++ insulin, GH, SS secretion
3. +ve inotrope.
• Regulation : Food Hs ANS stress & exercise glucocorticoids
Somatostatin
• GIT & Pancreas ( D cells)
• ++ by food & GIT hormones
• -- all hormones & GIT motility & secretions
Important Qs
• Why exercise is benefit for DM?
It lower blood by ++ cAMP-kinase w moves GLUT4.
• Why diuretics are contraindicated in DM?
K is important for insulin secretion, so
Diuretics -- K+ -- insulin secretion
Mechanism of Glucostasis
1. Liver (glycogenesis, glycogenolysis, gluconeogenesis).
2. Hormonal mechanism
• Insulin / glucagon
• Catecholamine, GH & cortisol
70-100 mg%
Glycogenolysis
Mechanism of Glucostasis
1. Liver 2. Hormonal mechanism• Insulin / glucagon• Catecholamine, GH & cortisol++ energy sources : ++ glucose (glycogenolysis,
gluconeogenesis with IR) ++ FFA, KB & aa