6-C homeostasis Flashcards
what is homeostasis?
maintenance of a stable internal environment.
what is negative feedback?
mechanism that restores a level back to normal
normal level -> level changes -> receptors detect change -> communication via nervous/hormonal system -> effectors respons -> normal level
what is positive feedback?
mechanism that amplifies a change away from the normal level in a system
normal level -> change level -> receptors detect change -> communication -> effectors respons -> back to changed level
what is the average conc. of glucose in the blood?
90 mg per 100cm3
where in the body is the blood glucose concentration controlled?
pancreas
what two hormones contol blood glucose concentration?
insulin and glucogen
what are hormones?
chemical messangers that travel in the blood to their tatget cells.
where in the pancreas is insulin and glucagon secreted?
the islets of Langerhans
what are the two cells in the islets of Langerhan and which hormone do the secrete?
beta cells - insulin
alpha cells - glucagon
what is glycogenolysis?
conversion of glycogen to glucose activated by glucogon and adrenaline
what is glycogenesis?
conversion of glucose to glycogen activated by insulin and inhibited by adrenaline
what is gluconeogenesis?
conversion of glycerol and amino acids to glucose activated by glucagon
what is the role of insulin?
lowers blood glucose conc when its too high
binds to specific receptors on the cell membranes of muscle and liver cells
increases permeability of muscle celles to glucose so more is uptaken
activates enzymes in muscle and liver cells to activate glycogenesis.
increases rate of respiration especially in muscel cells
what is the role of glucagon?
raises blood glucose conc when its too low
binds to receptors on liver cells and activates enzymes which control glycogenolysis
activates enzymes involved in gluconeogenesis
decreases rate of respiration
