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Negative Feedback Regulation of the Secretion of
Glucagon and Insulin
Process Diagrams Step-by-Step
Copyright © 2007 by John Wiley & Sons, Inc.
Low blood glucose(hypoglycemia)stimulates alphacells to secrete
1
GLUCAGON
Glucagon acts onhepatocytes(liver cells) to:
• convert glycogen into glucose (glycogenolysis)• form glucose from lactic acid and certain amino acids (gluconeogenesis)
Low blood glucose(hypoglycemia)stimulates alphacells to secrete
GLUCAGON
1
2
Glucagon acts onhepatocytes(liver cells) to:
• convert glycogen into glucose (glycogenolysis)• form glucose from lactic acid and certain amino acids (gluconeogenesis)
Glucose releasedby hepatocytesraises blood glucoselevel to normal
Low blood glucose(hypoglycemia)stimulates alphacells to secrete
GLUCAGON
1
2
3
Glucagon acts onhepatocytes(liver cells) to:
• convert glycogen into glucose (glycogenolysis)• form glucose from lactic acid and certain amino acids (gluconeogenesis)
Glucose releasedby hepatocytesraises blood glucoselevel to normal
If blood glucosecontinues to rise,hyperglycemia inhibitsrelease of glucagon
Low blood glucose(hypoglycemia)stimulates alphacells to secrete
GLUCAGON
1
2
3
4
Glucagon acts onhepatocytes(liver cells) to:
• convert glycogen into glucose (glycogenolysis)• form glucose from lactic acid and certain amino acids (gluconeogenesis)
Glucose releasedby hepatocytesraises blood glucoselevel to normal
If blood glucosecontinues to rise,hyperglycemia inhibitsrelease of glucagon
Low blood glucose(hypoglycemia)stimulates alphacells to secrete
High blood glucose(hyperglycemia)stimulates beta cellsto secrete
GLUCAGON
1 5
2
3
4
INSULIN
Insulin acts on variousbody cells to:
• accelerate facilitated diffusion of glucose into cells• speed conversion of glucose into glycogen (glycogenesis)• increase uptake of amino acids and increase protein synthesis• speed synthesis of fatty acids (lipogenesis)• slow glycogenolysis• slow gluconeogenesis
Glucagon acts onhepatocytes(liver cells) to:
• convert glycogen into glucose (glycogenolysis)• form glucose from lactic acid and certain amino acids (gluconeogenesis)
Glucose releasedby hepatocytesraises blood glucoselevel to normal
If blood glucosecontinues to rise,hyperglycemia inhibitsrelease of glucagon
Low blood glucose(hypoglycemia)stimulates alphacells to secrete
High blood glucose(hyperglycemia)stimulates beta cellsto secrete
INSULINGLUCAGON
1 5
2
3
4
6
Insulin acts on variousbody cells to:
• accelerate facilitated diffusion of glucose into cells• speed conversion of glucose into glycogen (glycogenesis)• increase uptake of amino acids and increase protein synthesis• speed synthesis of fatty acids (lipogenesis)• slow glycogenolysis• slow gluconeogenesis
Blood glucose level falls
Glucagon acts onhepatocytes(liver cells) to:
• convert glycogen into glucose (glycogenolysis)• form glucose from lactic acid and certain amino acids (gluconeogenesis)
Glucose releasedby hepatocytesraises blood glucoselevel to normal
If blood glucosecontinues to rise,hyperglycemia inhibitsrelease of glucagon
Low blood glucose(hypoglycemia)stimulates alphacells to secrete
High blood glucose(hyperglycemia)stimulates beta cellsto secrete
INSULINGLUCAGON
1 5
2
3
4
6
7
Insulin acts on variousbody cells to:
• accelerate facilitated diffusion of glucose into cells• speed conversion of glucose into glycogen (glycogenesis)• increase uptake of amino acids and increase protein synthesis• speed synthesis of fatty acids (lipogenesis)• slow glycogenolysis• slow gluconeogenesis
If blood glucose continuesto fall, hypoglycemiainhibits release ofinsulin
Blood glucose level falls
Glucagon acts onhepatocytes(liver cells) to:
• convert glycogen into glucose (glycogenolysis)• form glucose from lactic acid and certain amino acids (gluconeogenesis)
Glucose releasedby hepatocytesraises blood glucoselevel to normal
If blood glucosecontinues to rise,hyperglycemia inhibitsrelease of glucagon
Low blood glucose(hypoglycemia)stimulates alphacells to secrete
High blood glucose(hyperglycemia)stimulates beta cellsto secrete
INSULINGLUCAGON
1 5
2
3
4
6
7
8
