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GCSE Biology - Control of Blood Glucose Concentration #56 Regupation glucose regulation regulatio maintaining blood regulatiom levels regulatjon constant levels Effective post-workout nutrition the face of dynamic glucose intake and energy use by Glucose regulation body. Glucose, shown in figure 1 is key in Effective post-workout nutrition energy intake of Digestive health supplements. In Regulatiom to maintain this range there are two main hormones that control blood glucose levels: insulin and glucagon. Insulin is released when there are high amounts of glucose in the blood stream. Glucagon is released when there are low levels of glucose in the blood stream. There are other hormones that effect glucose regulation and are mainly controlled by the sympathetic nervous system. Blood glucose regulation is very important to the maintenance of the human body.Glucose regulation -
Glucagon and insulin are antagonistic hormones and somatostatin inhibits them both! It makes sense that they are all found close together. Before pancreatic hormones make it into circulation and act on tissues around the body, they first play a role in paracrine regulation of the pancreas itself. This paracrine feedback system is demonstrated in figure 3.
Take note of the signalling contrast between glucagon and insulin and somatostatin. Glucagon will always stimulate the release of the other two hormones, while insulin and somatostatin both have an inhibitory effect on the other hormones in this relationship.
Insulin and glucagon have opposing actions on one another, so if you learn one, you know the other! And remember that somatostatin will always inhibit both insulin and glucagon release.
Secretion of insulin, from beta cells within the islet of Langerhans, inhibits the surrounding alpha cells from releasing glucagon and the delta cells from releasing somatostatin. Secretion of glucagon, which is antagonistic to insulin, stimulates the delta cells to release somatostatin.
Interestingly, glucagon also activates the beta cells and stimulates insulin release. Considering insulin and glucagon have opposing actions throughout the body this may seem counterintuitive.
To better understand why this occurs imagine a runner nearing the end of a marathon — after running almost 42 kilometers, glucose within the body will be severely depleted. In order to correct this state of hypoglycaemia, alpha cells in the pancreas will release glucagon, resulting in the production and liberation of glucose from the liver and adipocytes.
Insulin is then needed to help cells around the body especially the skeletal muscle cells absorb the liberated glucose and use it for energy. This interplay between glucagon and insulin allows the runner to keep moving and finish the race!
It is also important to understand that not all regulatory signals are equal; the stimulatory effects that glucagon has on beta cells is much smaller than the stimulatory effects of increased blood sugar after eating a meal. Lastly, secretion of somatostatin within the islets inhibits the activity of both the beta and alpha cells.
Regulation of pancreatic hormones is a complex process, involving much more than just the paracrine feedback system within the islet of Langerhans.
Secretion of insulin and glucagon is controlled by the integration and interaction of multiple inputs including nutrients, hormones, neurotransmitters and drugs.
For both insulin and glucagon, changes in blood glucose concentrations are the primary stimuli that activates, or inhibits, their release.
Blood glucose is the regulated variable within this system, meaning it is constantly monitored by sensors i. receptors in the body and kept within a limited range through physiological mechanisms. When the body is in a state of hyperglycemia , and blood glucose levels are elevated, sensors in the pancreas detect this and stimulate the beta cells to increase their release of insulin.
When blood glucose levels drop, putting the body is in a state of hypoglycemia , the alpha cells are stimulated and glucagon is released.
The integration of blood glucose levels, and other regulatory stimuli, on alpha and beta cells is discussed in further detail below. The following figure depicts how insulin release is regulated by different inputs throughout the body.
Keep the big picture in mind. Which one of the following exhibits paracrine control? The following figure demonstrates how the release of glucagon from alpha cells is regulated by different inputs throughout the body.
Remember that both insulin and somatostatin will both inhibit the secretion of glucagon from alpha cells in the pancreas. The endocrine pancreas is always secreting some level of insulin and glucagon. Figure 6 below shows how plasma concentrations of glucose, glucagon and insulin change over a hour period.
Pay close attention to how these levels change before and after a meal and the relationships between the different plasma concentrations.
Think about the relationship between insulin, glucagon and glucose and what causes fluctuations to each. This diagram presents information that you have already learned in a new way! As one hormone increases its activity the other one decreases but is never completely shut off.
All inputs that regulate the activity of alpha and beta cells combine in the pancreas. The overall summation of these inputs determines if the system favours insulin or glucagon release. After eating a meal glucose levels rise.
In response to this the body increases the concentration of insulin in the blood and decreases the concentration of glucagon. The opposite effect is seen in between meals when blood glucose concentration decreases — now blood glucagon concentrations rise and insulin concentrations fall.
Take note that the concentration of both insulin and glucagon in the blood never reaches 0, there is always some level of hormone being secreted from the pancreas. We know that regardless of blood glucose levels, the concentrations of insulin and glucagon never reach zero.
Why do you think that is? Hint: Think about what would happen if you needed to produce a hormone quickly and it was not readily available. So far we have covered where insulin and glucagon come from, and how they are regulated.
Now we will dive into the effects these hormones have on the body. The absorptive state , or the fed state, occurs after a meal when your body is digesting the food and absorbing the nutrients.. Digestion begins the moment you put food into your mouth, as the food is broken down into its constituent parts to be absorbed through the intestine.
The digestion of carbohydrates begins in the mouth, whereas the digestion of proteins and fats begins in the stomach and small intestine. The constituent parts of these carbohydrates, fats, and proteins are transported across the intestinal wall and enter the bloodstream sugars and amino acids or the lymphatic system fats.
The ingestion of food and the rise of glucose concentrations in the bloodstream stimulate pancreatic beta cells to release insulin. For the purpose of this course we will focus on the effects of insulin in adipose tissue, skeletal muscle and the liver. Figure 7 below provides a visual representation of how the adipose tissue, skeletal muscle and liver respond to an increase in insulin, caused by high blood glucose levels.
Note the negative feedback that allows this response to be highly regulated. In adipose tissue, when insulin concentrations are low, glucose transport proteins are recycled slowly between the cell membrane and cell interior. Vesicles then fuse with the cell membrane and expose the GLUT4 transporters to the extracellular fluid.
Insulin also increases the activity of pyruvate dehydrogenase and acetylCoA carboxylase within adipocytes, facilitating the conversion of absorbed glucose into triglycerides for lipid storage.
In a similar fashion to adipose tissues, insulin causes the recruitment of GLUT4 transporters to the surface of skeletal muscle cells. Insulin further reduces blood glucose levels by stimulating glycolysis, the metabolism of glucose for generation of ATP, in the muscle.
This is achieved by activating the enzymes phosphofructokinase and pyruvate dehydrogenase. Insulin also stimulates skeletal muscle to convert excess glucose into glycogen for storage by activating glycogen synthase and it inhibits enzymes involved in glycogenolysis glycogen phosphorylase.
Lastly, insulin stimulates amino acids uptake and protein synthesis in the muscle tissue. Insulin increases absorption of blood glucose into hepatocytes by promoting the conversion of glucose into glucosephosphate G6P. This is achieved through activation of the enzyme glucokinase and inhibition of glucosephosphatase.
By immediately converting glucose into G6P, the cell can maintain a concentration gradient where glucose levels are higher in the blood and lower inside the cell. Insulin increases the activity of enzymes involved in glycogen synthesis glycogen synthase and inhibits enzymes used for glycogenolysis glycogen phosphorylase.
Once glycogen stores within the liver are filled, any remaining glucose is broken down and used for triglyceride synthesis and lipid storage. The figure below is an effective visual representation of the effects of insulin on liver, muscle and adipose cells in the absorptive state. Did you know not all cells require insulin for efficient uptake of glucose?
Red blood cells, as well as cells of the brain, liver, kidneys and lining of the small intestine do not require insulin for efficient uptake of glucose! The post-absorptive state , or the fasting state, occurs when food has been digested, absorbed, and stored.
You commonly fast overnight, but skipping meals during the day puts your body in the post absorptive state as well. During this state, the body must rely initially on stored glycogen.
Glucose levels in the blood begin to drop as it is absorbed and used by the cells. In response to the decrease in glucose, insulin levels also drop. Glycogen and triglyceride storage slows.
In response to a drop in blood glucose concentration, the hormone glucagon is released from the alpha cells of the pancreas. Glucagon acts upon primarily the liver and adipose cells. This diagram has a lot of processes and it can be a bit overwhelming to make sense of all of it at once. It is helpful to look at the big picture first, and then add in more details as you become more and more comfortable with the material.
When blood sugar levels drop glucagon stimulates the liver to convert its stores of glycogen back into glucose. This response is known as glycogenolysis and is achieved by increasing the activity of glycogen phosphorylase and decreasing the activity of glycogen synthase.
This glucose is then released from the liver to be used by the peripheral tissues and the brain. Glucagon responds to too low of a blood glucose level; it informs the tissue to release some glucose from the glycogen stores. Epinephrine prepares the muscles and respiratory system for activity in the case of a "fight or flight" response.
Lastly, cortisol supplies the body with fuel in times of heavy stress. If blood sugar levels remain too high the body suppresses appetite over the short term.
Long-term hyperglycemia causes many health problems including heart disease, cancer, [23] eye, kidney, and nerve damage. Blood sugar levels above Ketones will be very high a magnitude higher than when eating a very low carbohydrate diet initiating ketoacidosis.
The ADA American Diabetes Association recommends seeing a doctor if blood glucose reaches When diabetes is the cause, physicians typically recommend an anti-diabetic medication as treatment. From the perspective of the majority of patients, treatment with an old, well-understood diabetes drug such as metformin will be the safest, most effective, least expensive, and most comfortable route to managing the condition.
Treatment will vary for the distinct forms of Diabetes and can differ from person to person based on how they are reacting to treatment. Some medications may cause a rise in blood sugars of diabetics, such as steroid medications, including cortisone, hydrocortisone, prednisolone, prednisone, and dexamethasone.
Low blood sugar is very frequent among type 1 diabetics. There are several causes of low blood sugar, including, taking an excessive amount of insulin, not consuming enough carbohydrates, drinking alcohol, spending time at a high elevation, puberty, and menstruation.
Symptoms may include lethargy , impaired mental functioning; irritability ; shaking, twitching, weakness in arm and leg muscles; pale complexion; sweating; loss of consciousness. Mechanisms that restore satisfactory blood glucose levels after extreme hypoglycemia below 2. Without discounting the potentially quite serious conditions and risks due to or oftentimes accompanying hyperglycemia, especially in the long-term diabetes or pre-diabetes, obesity or overweight, hyperlipidemia , hypertension , etc.
This is especially the case for those organs that are metabolically active or that require a constant, regulated supply of blood sugar the liver and brain are examples. Symptomatic hypoglycemia is most likely associated with diabetes and liver disease especially overnight or postprandial , without treatment or with wrong treatment, possibly in combination with carbohydrate malabsorption, physical over-exertion or drugs.
Many other less likely illnesses, like cancer, could also be a reason. Starvation, possibly due to eating disorders, like anorexia, will also eventually lead to hypoglycemia. Hypoglycemic episodes can vary greatly between persons and from time to time, both in severity and swiftness of onset.
For severe cases, prompt medical assistance is essential, as damage to brain and other tissues and even death will result from sufficiently low blood-glucose levels.
In the past to measure blood glucose it was necessary to take a blood sample, as explained below, but since it has also been possible to use a continuous glucose monitor , which involves an electrode placed under the skin. Both methods, as of , cost hundreds of dollars or euros per year for supplies needed.
Glucose testing in a fasting individual shows comparable levels of glucose in arterial, venous, and capillary blood. But following meals, capillary and arterial blood glucose levels can be significantly higher than venous levels.
Glucose is measured in whole blood, plasma or serum. Historically, blood glucose values were given in terms of whole blood, but most laboratories now measure and report plasma or serum glucose levels.
Because red blood cells erythrocytes have a higher concentration of protein e. To convert from whole-blood glucose, multiplication by 1. To prevent contamination of the sample with intravenous fluids , particular care should be given to drawing blood samples from the arm opposite the one in which an intravenous line is inserted.
Alternatively, blood can be drawn from the same arm with an IV line after the IV has been turned off for at least 5 minutes, and the arm has been elevated to drain infused fluids away from the vein. The actual concentration of glucose in blood is very low, even in the hyperglycemic.
Two major methods have been used to measure glucose. The first, still in use in some places, is a chemical method exploiting the nonspecific reducing property of glucose in a reaction with an indicator substance that changes color when reduced. Since other blood compounds also have reducing properties e.
The more recent technique, using enzymes specific to glucose, is less susceptible to this kind of error.
The two most common employed enzymes are glucose oxidase and hexokinase. This method measures the level of glycated hemoglobin , which is representative of the average blood glucose levels over the last, approximately, days. In either case, the chemical system is commonly contained on a test strip which is inserted into a meter, and then has a blood sample applied.
Test-strip shapes and their exact chemical composition vary between meter systems and cannot be interchanged. Formerly, some test strips were read after timing and wiping away the blood sample by visual comparison against a color chart printed on the vial label.
Strips of this type are still used for urine glucose readings, but for blood glucose levels they are obsolete. Their error rates were, in any case, much higher. Errors when using test strips were often caused by the age of the strip or exposure to high temperatures or humidity.
Urine glucose readings, however taken, are much less useful. In properly functioning kidneys, glucose does not appear in urine until the renal threshold for glucose has been exceeded.
This is substantially above any normal glucose level, and is evidence of an existing severe hyperglycemic condition. However, as urine is stored in the bladder, any glucose in it might have been produced at any time since the last time the bladder was emptied. Since metabolic conditions change rapidly, as a result of any of several factors, this is delayed news and gives no warning of a developing condition.
Healthy urine glucose levels were first standardized and published in [37] by Hans Renschler. A noninvasive method of sampling to monitor glucose levels has emerged using an exhaled breath condensate.
However this method does need highly sensitive glucose biosensors. The fasting blood glucose level, which is measured after a fast of 8 hours, is the most commonly used indication of overall glucose homeostasis, largely because disturbing events such as food intake are avoided.
Conditions affecting glucose levels are shown in the table below. Abnormalities in these test results are due to problems in the multiple control mechanism of glucose regulation. The metabolic response to a carbohydrate challenge is conveniently assessed by a postprandial glucose level drawn 2 hours after a meal or a glucose load.
In addition, the glucose tolerance test, consisting of several timed measurements after a standardized amount of oral glucose intake, is used to aid in the diagnosis of diabetes.
Error rates for blood glucose measurements systems vary, depending on laboratories, and on the methods used. Colorimetry techniques can be biased by color changes in test strips from airborne or finger-borne contamination, perhaps or interference e.
Electrical techniques are less susceptible to these errors, though not to others. In home use, the most important issue is not accuracy, but trend. In the US, home use blood test meters must be approved by the federal Food and Drug Administration before they can be sold.
Finally, there are several influences on blood glucose level aside from food intake. Infection, for instance, tends to change blood glucose levels, as does stress either physical or psychological.
Exercise, especially if prolonged or long after the most recent meal, will have an effect as well. In the typical person, maintenance of blood glucose at near constant levels will nevertheless be quite effective. Contents move to sidebar hide. Article Talk. Read Edit View history.
At this point, you may be diagnosed with a condition called prediabetes. The pancreas tries to compensate by making more insulin, but over time, it becomes exhausted and eventually produces less insulin, leading to full-blown type 2 diabetes. According to the CDC, million Americans are living with diabetes Although people of all shapes and sizes can get Type 2 diabetes, it is strongly associated with abdominal obesity.
In the past, it was mainly diagnosed in older adults, but it is becoming more and more common in children and adolescents as well, as obesity has increased in all age groups. In the maps below, you can see that as obesity has increased in states around the country, so has diabetes. The complications of type 2 diabetes result from long-term exposure to high blood glucose, or hyperglycemia.
This causes damage to the heart, blood vessels, kidneys, eyes, and nerves, increasing the risk of heart disease and stroke, kidney failure, blindness, and nerve dysfunction.
People with uncontrolled Type 2 diabetes can also end up with foot infections and ulcers because of impaired nerve function and wound healing. If left untreated, this results in amputation. This video reviews the causes, complications, and treatments for type 2 diabetes.
Gestational diabetes is diabetes that develops during pregnancy in women that did not previously have diabetes. It affects approximately 6 percent of pregnancies in the U. It can cause pregnancy complications, mostly associated with excess fetal growth because of high blood glucose.
Although it usually goes away once the baby is born, women who have gestational diabetes are more likely to develop type 2 diabetes later in life, so it is a warning sign for them.
This video does a nice job of explaining the causes of the different types of diabetes. All of the following have been shown to help manage diabetes and reduce complications.
Nutrition Science and Everyday Application Callahan, Leonard, and Powell. Search site Search Search. Go back to previous article. Sign in. Hormones Involved in Blood Glucose Regulation Central to maintaining blood glucose homeostasis are two hormones, insulin and glucagon , both produced by the pancreas and released into the bloodstream in response to changes in blood glucose.
Insulin is made by the beta-cells of the pancreas and released when blood glucose is high. It causes cells around the body to take up glucose from the blood, resulting in lowering blood glucose concentrations.
Glucagon is made by the alpha-cells of the pancreas and released when blood glucose is low. It causes glycogen in the liver to break down, releasing glucose into the blood, resulting in raising blood glucose concentrations. Remember that glycogen is the storage form of glucose in animals.
In this image, cell nuclei are stained blue, insulin is stained red, and blood vessels are stained green. You can see that this islet is packed with insulin and sits right next to a blood vessel, so that it can secrete the two hormones, insulin and glucagon, into the blood.
This allows glucose to enter the cell, where it can be used in several ways. If the cell needs energy right away, it can metabolize glucose through cellular respiration, producing ATP step 5.
Alternatively, it can be converted to fat and stored in that form step 6. You receive messages from your brain and nervous system that you should eat. Glucagon is released from the pancreas into the bloodstream. In liver cells, it stimulates the breakdown of glycogen , releasing glucose into the blood.
In addition, glucagon stimulates a process called gluconeogenesis , in which new glucose is made from amino acids building blocks of protein in the liver and kidneys, also contributing to raising blood glucose. Glucose can be used to generate ATP for energy, or it can be stored in the form of glycogen or converted to fat for storage in adipose tissue.
Glucose, a 6-carbon molecule, is broken down to two 3-carbon molecules called pyruvate through a process called glycolysis. Pyruvate enters a mitochondrion of the cell, where it is converted to a molecule called acetyl CoA.
Acetyl CoA goes through a series of reactions called the Krebs cycle. This cycle requires oxygen and produces carbon dioxide. It also produces several important high energy electron carriers called NADH 2 and FADH 2.
These high energy electron carriers go through the electron transport chain to produce ATP—energy for the cell!
This section will give us reggulation look refulation Glucose regulation importance of maintaining blood glucose levels in the regulatjon and how Glucose regulation is regulated. Citrus aurantium and blood sugar control Effective post-workout nutrition learn about the processes Garlic for digestion hormones Gluten-free recipes in changing glucose concentrations in regulwtion blood. Effective post-workout nutrition will gain an understanding of the difference between insulin and glucagon and how and when they work to modify blood glucose levels to maintain homeostasis. Furthermore, you will learn how glucose is synthesized by various enzymes through gluconeogenesis and how glucose is broken down through the process of glycolysis. We will also explore the role of the pancreas in generating and secreting hormones necessary for glucose regulation. Several real-world examples will be given to further your understanding.
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