Physiology lecture on endocrine system physiology details insulin functions.
Hi, welcome to physiology open. try to solve this question on functions of insulin. in this question you have to state which statement is true and which statement is false. you can pause the video and think about the answers. we will come back to the question at the end of the video again. okay now let’s discuss the
Concepts on functions of insulin or effects of insulin on metabolism. excess fuel during times of their availability for future use. thus insulin is released in the fed state when the availability of the fuel especially are absorbed from gastrointestinal tract, their concentration in blood rises. however with
The release of the insulin they are quickly moved from the blood into their storage depots. so how does insulin promote the storage of nutrients? well before we go into the concepts we will just see in brief which metabolic cycles will decrease the nutrient concentration in blood and which will increase the concentration
In blood. factors which cause increase in blood glucose concentration are intake of food and then digestion and absorption of nutrients into the bloodstream, then glycogenolysis meaning breakdown of stored glycogen into glucose and then gluconeogenesis which causes synthesis of new glucose mainly from amino
Acids. now factors which cause decrease in blood glucose concentration are storage of glucose as glycogen that is glycogenesis which occurs mainly in liver and skeletal muscles. also storage of excess glucose as fatty acids. this also occurs in liver and finally utilization of glucose by peripheral tissues. similarly
For fats and proteins concentration is increased by lipolysis and proteolysis respectively and decreased by promoting their entry into cells and causing fatty acid synthesis and protein synthesis respectively. so logically you can tell from this blood insulin should promote glycogenesis, utilization of
Glucose by peripheral tissues gluconeogenesis. similarly it should promote fatty acid synthesis and storage and inhibit lipolysis and it should also increase protein synthesis and inhibit proteolysis. so what it specifically does to have these effects. well this all happens skeletal muscles and adipose tissue. in
Liver it increases the activity of enzyme glucokinase which converts glucose to glucose 6-phosphate thus it keeps the concentration of glucose low in the liver so that glucose can enter the hepatocytes. the activity of the enzyme glycogen synthase while it inhibits glycogenolysis by inhibiting glycogen
Phosphorylase. also excess glucose which has not been converted into glycogen enters into glycolysis pathway and produces acetyl coenzyme a in liver. now this acetyl coenzyme a is used for synthesis of fatty acids. since insulin promotes the activity of the enzyme acetyl coa carboxylase- which is very important enzyme in
Lipogenesis and hence insulin promotes fatty acid synthesis also. in the process of synthesis of fatty acids malonylcoa is formed which inhibits carnitine palmitoyl transferase enzyme that is cpt enzyme present on the membrane of mitochondria which causes entry of fatty acids into the mitochondria. so when
This enzyme is inhibited beta oxidation of fatty acid doesn’t occur. so what is happening only synthesis of fats is occurring from extra glucose. well now the formed fatty acid should now go and get stored in their depots that is adipose tissue. so they are transported from liver to adipose tissue as triacylglycerol in
Vldl via blood. insulin increases the expression of lipoprotein lipase in the walls of capillaries of adipose tissue. this lipoprotein lipase releases which then enter into the adipose tissue and insulin in liver and some on adipose tissue. now insulin also promotes the entry of glucose in most cells except
Neurons and rbcs. it does which are present inside the cell to the membrane. since glucose is in higher concentration in blood it enters in those cells along its concentration gradient via these glut4 transporters by using glucose as a fuel in presence of insulin and hence usage of fats as fuel is spared. we
Have already seen that beta oxidation is not occurring insulin increases the entry of glucose into hepatocytes also but not by increasing these glut4 transporters instead by increasing the activity of glucokinase enzyme right ! anyways now in skeletal muscles excess glucose is also stored as glycogen while in
Adipose tissue the glucose which enters acts as a substrate for glycerol portion of triacylglycerol. we have already seen that fatty acids from vldl enter the adipose tissue so the glycerol from glucose and fatty acids combine to form triacylglycerol in adipose tissue. triacylglycerols in adipose tissue. also
In fat cells. this lipase breaks down stored triacylglycerol into fatty acids and glycerol. thus by inhibiting hormone sensitive lipase in adipose tissue. so we have seen two lipases of fatty acids into the adipose tissue- this is promoted by insulin and the one causing lysis of triacylglycerol from adipose tissue
-That is hormone sensitive lipase -it is inhibited by insulin. okay now what about its action on protein uptake by cells and promotes protein synthesis simultaneously inhibiting their breakdown. well now let’s come back to our original question. are correct -we have seen that glucose is fatty acids in
Liver and then fatty acids to adipose tissue where lipoprotein lipase facilitates the entry of fatty acids into the tissue. well the third statement is wrong since insulin spares the use of fatty acid instead it promotes its synthesis. fourth statement is also wrong since we have seen that in liver insulin
Increases the activity of the enzyme glucokinase due to which glucose entry into hepatocytes is increased. well thanks for watching the video to the channel physiology open. thank you
Transcribed from video
Insulin function physiology | Actions of insulin | Endocrine physiology By Physiology Open
