Hormonal communication Flashcards
Endocrine gland
Exocrine gland
-release hormones directly into blood (ductless)
-release hormones into a duct
Types of hormone
-Protein eg. insulin/glucagon can’t pass through bilayer so bind to membrane and release 2nd messenger
-Steroid eg. testosterone/ oestrogen can pass through bilayer as are fat soluble
Activation of 2nd messengers
-protein hormone binds to receptor on membrane activation G protein
-G protein activates adenyl cyclase (effector)
-adenyl cyclase converts ATP to cAMP (2nd messenger)
-cAMP initiates cascade of enzyme reactions or acts on proteins
Adrenal glands
-2 triangular shaped glands
-above each kidney
-adrenal cortex, adrenal medulla
Adrenal cortex
-controlled by hormones from pituitary gland
-secrete steroid hormones
3 layers
-zona glomerulosa- outer layer, secretes mineralocorticoids eg. aldosterone- controls Na and K conc. in blood+ blood pressure
-zona fasiculata- middle layer, secretes glucocorticoids eg. cortisol- controls metabolism
-zona reticularis- inner layer, secretes precursor molecules which taken up by ovaries/testes to make sex hormones, can secrete cortisol
How hormones from adrenal cortex enter cells
-steroid hormone passes plasma membrane
-binds to receptor in cytoplasm
-steroid hormone- receptor complex forms and moves through nuclear envelope + binds with receptor on chromosomal material
-stimulates mRNA production for protein synthesis
Adrenal medulla
-releases protein hormones eg adrenaline/ noradrenaline
-adrenaline polar so can’t pass through plasma membrane
-instead its detected by receptors on plasma membrane
Adrenaline causes
-smooth muscle in bronchioles to relax
-increase stroke volume of heart
-increase heart rate
-vasoconstriction to increase BP
-conversion of glycogen to glucose
-dilate pupils
-inhibiting gut action
Pancreas
-Endocrine function- releases hormones eg. insulin, glucagon from islets of langerhan into blood
-Exocrine function- enzymes eg. lipase, amylase, trypsinogen
Islets of langerhan
-control blood glucose
-majority is B cells which secrete insulin
-a cells secrete glucagon
Secretion of insulin
-membrane has K+ and Ca2+ channels
-K+ channels open so K+ diffuses out of cell, making negative(-70mV)
-blood glucose conc. rises, glucose enters cell
-glucose converted to ATP in respiration
-ATP causes K+ channels to close, so K+ accumulates in cell
-This causes potential doffernce to be less negative
-this opens voltage gated Ca2+ channels, so Ca2+ diffuses in
-Ca2+ causes vesicles to fuse with surface membrane and release insulin via exocytosis
Acini
-cells outside of islet of langerhan
-they secrete enzymes into tubule
Action of insulin on liver cell
-insulin binds to receptor
-enzyme tyrosine kinase is activated
-causes phosphorylation of inactive enzymes to active enzymes
-this causes cascade of enzyme controlled reactions eg. vesicle containing glucose transporter is inserted into membrane so more glucose leaves blood and enters cell
Effects of insulin on cell
-more transporter proteins on surface membrane
-glucose converted to glycogen
-more glucose enters cell
-more glucose converted to fats
-more glucose used in respiration
Blood glucose high
-detected by B cells
-these secrete insulin into the blood
-A cells secrete less glucagon
-their target cells are liver + muscle cells
-target cells have insulin receptors
-when insulin binds, tyrosine kinase is activated
-this causes phosphorylation of inactive enzymes
-this leads to a cascade of enzyme controlled reactions
Blood glucose low
-detected by A cells
-A cells secrete glucagon
-B cells secrete less insulin
-glucagon binds to receptors on liver cells
-this activates enzyme that catalyses conversion of glycogen to glucose via a cascade of enzyme controlled reactions
-this is called glycogenolysis
-glucagon also stimulates the conversion of amino acids and glycerol to glucose
-this is called gluconeogenesis
