BIOL2108H - Blood Glucose Regulation

our cells need…

a steady supply of glucose from the bloodstream

regulation of homeostasis involves

negative feedback (cycle with control center, effector organ, receptor)

receptors

monitor the physiological state (receive information)

control center

where information is processed and orders sent out

effectors

the organ that actually changes the physiological state

neurons

-some neurons are activated by glucose, while others are inhibited by glucose

-these neurons are connected to the pancreas to trigger insulin vs glucagon production

recall

glucose an only enter cells through glucose transporters

insulin causes glucose transporters to be moved to cell membrane

-insulin binds to its extracellular receptor changing its shape

-phosphorylation of intracellular portion of receptor

-chemical cascades send messages throughout the cell

-moves GLUT-4 transporter vesicle to the plasma membrane

-glucose channels open and glucose enters cell

-insulin breaks down and GLUT4 turns back into a vesicle channels close)

recall

excess glucose is stored as glycogen in liver cells

glucagon activates the enzyme that breaks down glycogen in the liver

-binds to extracellular receptor on liver cell

-receptor undergoes conformational change

-triggers a cascade of second messenger molecules

-activates the enzyme that converts glycogen into glucose

-glucose re-enters blood stream

-glucagon breaks down and enzyme turns back to inactive form