biology - topic 6 - control of blood glucose

exocrine glands

secrete substances into duct that carries them to site of action

endocrine glands

ductless, secrete hormones directly into blood in capillaries inside gland

hormones

molecules released by endocrine glands that affect activity of specific target cells/tissues/organs

steroid hormones

e.g. oestrogen - receptors located in cytoplasm as oestrogen is non polar

polypeptide hormones

e.g. insulin - receptors located in CSM as insulin is polar

hormone process

transported through body, bind to specific receptor on target cell that has complementary shape. transmission of signal inside cell by receptor or by second messenger leading to a cell response.

alpha cells

secrete glucagon

beta cells

secrete insulin

rise in blood glucose…

detected by b cells in islets of langerhans. b cells secrete insulin into blood, detected by receptors on liver and muscle cells. liver and muscle cells remove glucose from blood by increasing the number of glucose carrier proteins on surface, glycogenesis, increasing the rate of respiration.

fall in blood glucose…

detected by a cells in islets of langerhans. a cells secrete insulin into blood, detected by receptors on liver cells. hydrolytic enzymes carry out glycogenolysis, and glucose production activated from glycerol and amino acids = gluconeogenesis. decreased rate of respiration in cells.

adrenaline increases blood glucose conc by…

activating glycogenolysis, inhibiting glycogenesis, activating glucagon secretion, inhibiting insulin secretion

insulin secretion

glucose levels rise and diffuse into b cells via facilitated diffusion where it is phosphorylated and enters glycolysis, generating atp. atp closes k+ channels. k+ cannot diffuse out of cell so membrane potential changes. ca2+ channels open so more enters down conc gradient, causing vesicles to move to CSM and insulin secreted via exocytosis