in this video we're going to examine the postabsorptive state that is usually all night early in the mornings late at night more than 4 hours after the meal and during this period of time the catabolism of fat glycogen and proteins is far exceeding the anabolism of the same three so the ultimate goal is to ensure that you maintain a fairly consistent blood glucose level in between meals and that you're making glucose available via the blood to the cells of the body that primarily use glucose as an energy source so during this time we're sort of promoting the use of fats for energy and we're more sparingly using glucose via uh the reason being is that we're saving that glucose for the cells that absolutely need it that only use glucose as an energy source like the neurons in the brain so what are some of the sources of glucose well glycogenolyis which is a process we talked about earlier this is going to occur in the liver and the skeletal muscle so recall glycogenolyis is really the conversion ultimately of glycogen into glucose now during this chemical reaction we actually generate glucose 6 phosphate which is the first step of glycolysis so this actually gets us one extra ATP through this process than if we had just use glucose alone we also have lipolyis which is the breakdown of lipids in the liver as well as in the atapose tissue now when we're breaking down lipids remember we're primarily focusing on triglycerides as that's what we're storing fats as and those triglycerides get broken down into glycerol and into fatty acids so the glycerol is primarily going to be used as that intermediate right because we can convert that into G3P and then reverse engineer glucose so it allows for gluconneogenesis we could also break down cellular proteins at a higher rate than we're building them up and so proteins can be a major source of energy during prolonged periods of fasting so ultimately it's the amount of fat in a person's body that determines how long one can survive without food so here we have again the flowchart and a lot of it is central or centralized along the liver so the liver is going to be integral in glycogenolis it's integral in gluconneioenesis it's integral in protein catabolism uh it's helping to regulate ultimately those pools of nutrients that are available to all the other cells so what are some of the hormonal controls that are involved well the reverse is going to happen remember with the absorptive state it was primarily the parasympathetic nervous system so here it's going to be the sympathetic nervous system that is going to be controlling and interacting with hormones during this more complex post-absorptive state now a glut of insulin excuse me a glut of glucose so high levels of glucose was sort of the trigger for the absorptive state the post-absorptive state is going to be triggered by a reduction of glucose as measured by a reduction in insulin release so there are instances where moderate intakes of wine beer gin during or before a meal that can lead to more efficient use of insulin they help to lower the blood glucose level without a corresponding increase in insulin release but ultimately the hormone that matters here is glucagon so this is the antagonistic hormone to insulin so glucagon is referred to as a hyperglycemic hormone because it helps to stimulate a rise in glucose levels and it is stimulated by a hypoglycemic state or when you have declining blood glucose levels so let's examine the effects of glucagon so glucagon signals to the hpatoytes to promote glycogenolyis the breakdown of glycogen as well as gluconneogenesis it triggers the atapose cells to promote lipolyis so you generate fatty acids so you have fatty acids in circulation and then lastly it's going to target tissues like the muscle and it's going to start to break down or promote the breakdown of cellular protein so you can have a higher amount of amino acids which you in turn use for gluconneogenesis now we can when we look at glucagon glucagon does help modulate the effects glucose has after a high protein low high protein low carbohydrate meal so rising blood amino acid levels is going to trigger both insulin and glucagon release now there really really isn't an issue if the meal is well balanced but let's look at that scenario where you have a high protein low carbohydrate meal you're going to have an increased stimulus of insulin and because of that if it's not counterbalanced it can lead to hypoglycemia so lower blood glucose levels and that impacts the nervous system specifically in the brain so it can ultimately lead to brain damage since we're not providing an adequate amount of sugar to those neural cells now if it's fairly balanced uh and counterbalanced by glucagon that helps to stabilize glucose levels since glucagon is promoting glycogenolis and gluconneogenesis now the atapost cells are inervated by the sympathetic nervous system so it can help to supply quickly that stimulation of those atapost tissues can stimulate the breakdown of lipids and therefore provide glucose if blood glucose levels are low so low plasma levels of glucose uh or the fightor-flight response or even exercise can lead to a greater breakdown of fats or what we call fat mobilization and glycogenolis uh so the hormone associated with fight or flight is epinephrine or some some people might know it as adrenaline okay so the metabolism and the nutrients are also going to be impacted by other hormones like growth hormone thyroxine which is the metabolic hormone released by the thyroid sex hormones and corticosteroids