Exercise Metabolism We learned earlier this semester that the endocrine and nervous systems work together to maintain homeostasis within the body. As we have seen in previous chapters, the nervous system uses electrical impulses to communicate with the different muscles of the body and produce responses. The endocrine system, on the other hand, uses chemical signals called hormones that also produce responses. In this essay we will focus on the main hormones during exercise metabolism, therefore mainly on the endocrine system. Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an Original Essay One of the very first things we learned during this class unit is the definition of metabolism which is the sum of all chemical processes in the body. Now, before we get into the discussion of different hormones during exercise metabolism, we need to know more about hormones and how they work. There are many hormones in the body and each one is released by a specific gland in the body which is then circulated in the blood where they bind to specific receptors where they produce many chemical signals and, depending on the hormone released, this can speed up, increase or slow down the enzymatic activity. Enzymes are controlled by hormones and these control the rate of activity. There are two parts to metabolism. We have the breakdown of molecules which is catabolism and the synthesis of molecules which is called anabolism. You will see later that catabolic reactions usually have the word lysis which means to divide or break down while synthesis reactions usually do not always have the word genesis which basically means to create. During exercise our body produces work and to produce work we need energy which comes from adenosine triphosphate (ATP). By breaking down ATP we can obtain enough energy to meet our demands. We also need to consider how to replenish this ATP that has been used to produce energy and this occurs through phosphogen, glycolysis and the oxidative system. As a refresher, the phosphogen system is the fastest way to synthesize ATP and is used for very intense exercise. lasts up to 10 seconds and is based on creatine phosphate (enzyme) and when this runs out the body must use other systems. The glycolysis system is the next fastest and provides ATP for 1-3 minutes of intense exercise. Very quickly, as I said before, glycolysis is the final lysis, so it's the breakdown of glucose to provide energy and in the beginning it uses glucose directly from the blood. The oxidative system takes longer to create ATP but produces more of it and this is usually used for low intensity exercise. In prolonged exercise where the intensity is low, the body will likely use fat as an energy source instead of muscle glycogen (storage form of glucose) and blood glucose as a sort of backup plan. The catabolic hormones discussed in class that occur during resistance exercises were epinephrine, norepinephrine, glucagon, thyroxine, and cortisol (which also has some anabolic reactions). These hormones are called catabolic hormones because they break down molecules. Epinephrine and noepinephrine are very important hormones. Both are extremely important in helping the sympathetic nervous system, also known as fire and flight, produce energy and maintain bodily function during endurance exercise. Both of these hormones are called catecholamines and are very similar. Epinephrine, also sometimes called epinephrine, is produced by the medulla ofadrenal gland and this hormone increases blood glucose levels by breaking down glycogen stores in the liver and muscles for energy and this is called glycogenolysis. Both epinephrine and norepinephrine function as neurotransmitters which are chemical messengers that communicate with the brain and transmit signals between neurons. As for acting asThe effects of hormones last longer because their removal from the blood is slow compared to rapid reuptake. Once the exercise is finished, adrenaline returns to normal concentrations within a few minutes, while norepinephrine returns to normal only after several hours. In particular, adrenaline and norepinephrine bind to a specific receptor on the plasma membrane and this activates an enzyme called adenyl cyclase which breaks down ATP into cyclic AMP. Cyclic AMP then activates the protein kinase and this specific molecule causes the addition of a phosphate (high energy bond) to the phosphorylase and synthase. When a phosphate group is added to the phosphorylase, this will cause the phosphate to be activated, and once activated, this enzyme acts on glycogen to eliminate a glucose molecule in the muscle or liver and this glucose will be used for energy. On the other hand phosphate is also added to the synthase and this acts on the glycogen to add together a glucose molecule for glycogen storage. During exercise the amount of adrenaline increases and this accelerates phosphorylase and slows down synthase, so more energy is produced during exercise. So when there is more adrenaline there is an increase in blood glucose. Carbohydrate metabolism initially burns slowly and as the duration of exercise increases carbohydrates burn faster. Glucose available in the blood, released by the kidneys, and glucose released by the liver enter the cell via a muscle transporter protein GLUT 4 where it is phosphorylated once inside the muscle and this causes entrapment. From here if the muscle is not active it will be stored as glycogen, when active the glucose will go through glycolysis where the end product will be 2 pyruvate and this will produce atp which can be used in cross bridges and pumps. On the other hand, when blood glucose decreases, muscle glycogen will be phosphorylated and also create pyruvate to go through glycolysis for energy. Furthermore, in fat metabolism we have lipolysis which is the breakdown of triglycerides into 3 free fatty acids and glycerol using the lipase enzyme, so this increases when adrenaline increases. Then free fatty acids can be oxidized to produce ATP for energy, or they can be used in the synthesis of glucose from non-carbohydrates (gluconeogenesis) which again can act as an energy source by increasing blood glucose levels. Adrenaline and norepinephrine build muscle and burn fat for hours after training and, assuming you have a good diet, could last about five days and are best used with high-intensity activity (). Finally, when you exercise you put stress on your body and with this stress comes an increase in epinephrine in the blood to speed up your heart rate, breathing, blood pressure and metabolism so there is an increase in your metabolic rate and more calories you get. they burn. If epinephrine and norepinephrine were high enough, this could stimulate glucagon which would increase (sort of take over) glucose to help fuel anaerobic metabolism(). This hormone comes from the alpha cells of the pancreas and is basically an antagonist of insulin (which is controlled by the beta cells of the pancreas). Glucagon is importantin the liver and prevents blood glucose from falling too low. This hormone will do this by converting glycogen stored in the liver into glucose that can be released into the blood (hepatic glycogenolysis). Remember from earlier we talked about phosphorylase where a phosphate group is added to the phosphorylase, this in return makes the phosphorylase active and will act on glycogen and remove glucose, so when glucagon increases, this phosphorylase enzyme will increase to increase glucose levels in the blood. Not only does it break down glycogen but it can also stop the amount of glucose entering the liver and this can be very helpful in maintaining blood glucose levels. Subsequently, glucagon increases blood glucose levels through gluconeogenesis and does so by breaking down amino acids into glucose. Glucagon can also break down triglycerides from stored fats into free fatty acids where it can be converted into glucose and produce energy. With exercise lasting thirty minutes or more, the body somehow tries to maintain glucose concentrations while insulin concentrations decline. During exercise glucagon will increase during exercise and does so through hepatic glycogenolysis. This happens because there is an increase in the ability to bind to receptors on muscle cells and this increases during exercise due to increased blood flow. During exercise lasting several hours there is a significant increase in glucagon which uses gluconeogenesis to provide more energy during carbohydrate metabolism, but tremendous glucose depletion occurs during the late phase of activity as liver glycogen depletes runs out. Thyroxine was mentioned a little but not much in class, but this hormone is released by the thyroid gland and releases two nonsteroidal hormones triiodothyronine and thyroxine T4. Both of these hormones increase the metabolic rate of all tissues and significantly increase it up to 60-100%. (105). These hormones not only do this, but increase protein synthesis, mitochondria, glucose uptake, glycolysis, gluconeogenesis, and the availability of free fatty acids. During physical activity, thyroxine increases, but during prolonged exercise, thyroxine increases significantly and remains constant. As for cortisol, this steroid hormone is produced by the adrenal cortex and we learned in class that it treats inflammation. Cortisol increases fuel by stimulating gluconeogenesis in the liver and increases the breakdown of triglycerides into free fatty acids and glycerol where it can be used to convert to glucose. There is also protein catabolism and as the name suggests, it is the breakdown of proteins into amino acids and these amino acids can be used to convert into glucose and are used to repair and create more enzymes. There is one exception where cortisol acts as an anabolic hormone and that is to decrease glucose uptake and one of the main reasons it does this is to save some of the glucose for the brain. Cortisol not only carries out gluconeogenesis, or the production of new glucose, but also plays a role in using free fatty acids for energy when performing endurance exercise. Cortisol peaks thirty to forty-five minutes of exercise and then drops to normal levels. The next three hormones I'll talk about are insulin, growth hormone, and testosterone, all of which are anabolic hormones, while insulin and growth hormone have exceptions. Testosterone wasn't mentioned much in class, but it is a steroid hormone that is produced in the ovaries in women and the testes in men along with the adrenal gland in both.