5.1.4 hormonal communication NOT ON MOCK Flashcards Preview

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what is endocrine communication

specialised glands secrete hormones into bloodstream

circulatory system carries hormone to target cell

lipid-double steroid hormones diffuse into cell and bind to complementary receptor in cytoplasm. peptide hormones bind to complementary receptor on cell surface membrane


describe the structure of the adrenal glands

located above kidneys


what hormone does the medulla secrete

adrenaline in response to danger, stress or excitement as part of the fight or flight response


which hormones does the cortex secrete

mineralocorticoids eg aldosterone which targets kidney and gut to control concentration of Na+ and K+ ions in blood

glucocorticoids eg cortisol and corticosterone which stimulate an increase in blood glucose concentration


why is it important that blood glucose concentration remains stable

maintain constant blood water potential: prevent osmotic lysis / cremation of cells

maintain constant concentration of respiratory substrate : organism maintains constant level of activity regardless of environmental conditions


define negative feedback

self-regulatory mechanisms return internal environment to optimum when there is a fluctuation

different mechanisms are responsible for dealing with an increase / decrease in normal level for greater control


define glycogenesis

liver converts glucose into the storage polymer glycogen


define glycogenolysis

liver hydrolyses glycogen into glucose which can diffuse into blood


define gluconeogenesis

liver converts glycerol and amino acids into glucose


outline the role of glucagon when blood glucose concentration decreases

alpha cells in islets of langerhans in pancreas detect decrease and secret glucagon into bloodstream

glucagon binds to surface receptors on liver cells and activates enzymes for glycogenolysis and gluconeogenesis

glucose diffuses from liver into blood stream

alpha cells detect that blood glucose concentration has returned to optimum and stop producing glucagon (negative feedback) cells


use the secondary messenger model to explain how glucagon works

hormone receptor complex forms

conformational change to receptor activates g-protein

activates adenylate cyclase, which converts ATP to cAMP (cyclic AMP)

cAMP activates protein kinase A pathway

results in glycogenolysis


outline what happens when blood glucose concentration increases

beta cells in islets of langerhans in pancreas detect increase and secrete insulin into bloodstream

insulin binds to surface receptors on target cells to : increase cellular glucose uptake, activate enzymes for glycogenesis (liver and muscles), stimulate adipose tissue to synthesise fat.


describe how insulin leads to a decrease in blood glucose concentration

increases permeability of cells to glucose

increases glucose concentration gradient

triggers inhibition of enzymes for glycogenolysis


how is insulin secretion controlled

beta cells have K* and Ca2+ ion channels to maintain potential difference -70mV

as glucose concentration increases, glucose enters beta cells via facilitated diffusion

respiration of glucose produces ATP. ATP-gated K+ ion channels close, so K+ ions not longer diffuse out of cell

potential difference in cell becomes more positive = depolarisation . Ca 2+ ion channels open. Ca2+ triggers exocytosis of insulin


describe the exocrine function of the pancreas

secretes digestive enzymes eg amylase, trypsin and lipase to the duodenum via the pancreatic tract


explain the causes of type 1 diabetes mellitus and how it can be controlled

body cannot produce insulin eg due to autoimmune response which attacks beta cells of islets of langerhans

treat by injecting insulin from animal source of genetically modified bacteria. possible future treatment: use stem cells to produce new beta cells


explain the causes of type 2 diabetes mellitus and how it can be controlled

glycoprotein receptors are damaged or become less responsive to insulin

strong positive correlation with poor diet / obesity

treat by controlling diet and exercise regime