June 4, 2023

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