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What Do Insulin And Glucagon Regulate

Islets Of Langerhans

Islets Of Langerhans

Islets of Langerhans, also called islands of Langerhans, irregularly shaped patches of endocrine tissue located within the pancreas of most vertebrates. They are named for the German physician Paul Langerhans, who first described them in 1869. The normal human pancreas contains about 1,000,000 islets. The islets consist of four distinct cell types, of which three (alpha, beta, and delta cells) produce important hormones; the fourth component (C cells) has no known function. The most common islet cell, the beta cell, produces insulin, the major hormone in the regulation of carbohydrate, fat, and protein metabolism. Insulin is crucial in several metabolic processes: it promotes the uptake and metabolism of glucose by the body’s cells; it prevents release of glucose by the liver; it causes muscle cells to take up amino acids, the basic components of protein; and it inhibits the breakdown and release of fats. The release of insulin from the beta cells can be triggered by growth hormone (somatotropin) or by glucagon, but the most important stimulator of insulin release is glucose; when the blood glucose level increases—as it does after a meal—insulin is released to counter it. The inability of the islet cells to make insulin or the failure to produce amounts sufficient to control blood glucose level are the causes of diabetes mellitus. The alpha cells of the islets of Langerhans produce an opposing hormone, glucagon, which releases glucose from the liver and fatty acids from fat tissue. In turn, glucose and free fatty acids favour insulin release and inhibit glucagon release. The delta cells produce somatostatin, a strong inhibitor of somatotropin, insulin, and glucagon; its role in metabolic regulation is not yet clear. Somatostatin is also produced by the hypothalamu Continue reading >>

Regulation Of Body Processes

Regulation Of Body Processes

Hormonal Regulation of the Excretory System The contrasting actions of antidiruetic hormone and aldosterone work to regulate the level of water in the body. Learning Objectives Explain how the actions of different hormones regulate the excretory system Key Takeaways The hypothalamus monitors the amount of water in the body by sensing the concentration of electrolytes in the blood; a high concentration of electrolytes means that the level of water in the body is low. Antidiuretic hormone (ADH), produced by the hypothalamus and released by the posterior pituitary, causes more water to be retained by the kidneys when water levels in the body are low. ADH effects water retention by creating special channels for water, called aquaporins, inside the kidneys so that more water can be reabsorbed before it is excreted. Aldosterone, produced by the adrenal cortex, causes the retention of water in the body by increasing the levels of sodium and potassium ions in the blood, which causes the body to reabsorb more water. When blood pressure is low, the enzyme renin is released, which cleaves the protein angiotensinogen into angiotensin I, which is further converted into angiotensin II. Angiotensin II signals the adrenal cortex to release aldosterone, which then increases the retention of sodium ions, enhancing the secretion of postassium ions, resulting in water retention and an increase in blood pressure. renin: a circulating enzyme released by mammalian kidneys that converts angiotensinogen to angiotensin-I that plays a role in maintaining blood pressure mineralocorticoid: any of a group of steroid hormones, characterised by their similarity to aldosterone and their influence on salt and water metabolism electrolyte: any of the various ions (such as sodium or chloride) that regulat Continue reading >>

The Role Of Glucose, Insulin And Glucagon In The Regulation Of Food Intake And Body Weight.

The Role Of Glucose, Insulin And Glucagon In The Regulation Of Food Intake And Body Weight.

Abstract Glucose and related pancreatic hormones play a major role in the metabolism of monogastric mammals yet their influence on hunger and/or satiety is, as yet, poorly understood. Glucose, insulin and glucagon rise during a meal and gradually decline to baseline levels shortly after a meal. A sudden drop in plasma glucose as well as insulin have been reported just prior to the onset of a meal but the functional significance of this is not yet clear. Systemic injections of glucose have no acute satiety effects but intraduodenal and intrahepatic infusions reduce food intake and free-feeding and deprived animals respectively. Treatments which decrease cellular glucose utilization directly (2-DG) or indirectly (insulin) increase food intake while exogenous glucagon (which produces hyperglycemia) decreases it. There is considerable evidence that some or all of these effects may be due to a direct central action of glucose, 2-DG, insulin, and glucagon on brain mechanisms concerned with the regulation of hunger and satiety although influences on peripheral "glucoreceptors" have been demonstrated as well. The functional significance of glucoprivic feeding is, however, questioned. The feeding response to 2-DG and related compounds is capricious, and its temporal course does not parallel the hyperglycemic reaction which presumably reflects cellular glucopenia. Moreover, numerous brain lesions which increase, decrease, or have no effect on ad lib intake and often have no effect on the response to deprivation have been shown to severely impair or abolish feeding responses to systemic injections of 2-DG that produce severe central as well as peripheral glucopenia. Feeding responses to insulin are intact after most of these lesions, suggesting that this hormone may influence food Continue reading >>

What Is Glucagon?

What Is Glucagon?

Blood sugar levels are an important part of overall health. When blood sugar levels drop, an individual may feel lethargic. If they drop too low, the individual may become disoriented, dizzy or even pass out. Blood sugar control involves a complex system of hormones, and one of those hormones is glucagon. Glucagon is a hormone that works with other hormones and bodily functions to control glucose levels in the blood. It comes from alpha cells found in the pancreas and is closely related to insulin-secreting beta cells, making it a crucial component that keeps the body’s blood glucose levels stable. What does glucagon do? Although secreted by the pancreas, glucagon directly impacts the liver as it works to control blood sugar levels. Specifically, glucagon prevents blood glucose levels from dropping to a dangerous point by stimulating the conversion of stored glycogen to glucose in the liver. This glucose can be released into the bloodstream, a process known as glycogenolysis. Secondly, glucagon stops the liver from consuming some glucose. This helps more glucose to enter the bloodstream, rather than being consumed by the liver, to keep levels stable. Finally, glucagon works in a process known as gluconeogenesis, which is the production of glucose in the amino acid molecules. In each of these processes, glucagon and insulin work together. Insulin will prevent glucose levels from increasing to a point that is too high, while glucagon prevents it from dropping too low. Glucagon production is stimulated when an individual eats a protein-rich meal, experiences a surge in adrenaline, or has a low blood sugar event. Potential problems with glucagon function Glucagon function is crucial to proper blood glucose levels, so problems with glucagon production will lead to problems Continue reading >>

Insulin And Glucagon: Essential Hormones For Normal Blood Sugar

Insulin And Glucagon: Essential Hormones For Normal Blood Sugar

When it comes to regulating blood glucose levels there is an important interplay between two hormones in your body, insulin and glucagon. These two hormones counterbalance each other and allow for normal blood sugar balancing. When they are not working correctly people can develop insulin resistance and diabetes. Here are the major players. Glucose is a simple form of sugar that is used by our cells as fuel. When you eat a meal your food is broken down in your digestive system into its building blocks and ultimately converted into glucose. Glucose is then released into your blood stream so that your cells can use it for fuel to do their jobs in your body. When there is extra glucose in the blood stream it is taken up into the liver and muscle cells to be stored as glycogen for in between meals. Insulin is a hormone that is released from your pancreas in response to high amounts of glucose circulating in your blood. The purpose of insulin is to help the high glucose levels leave your bloodstream and enter your cells. Insulin acts as a key to open the cell membranes of the cells so glucose can enter. This causes the blood glucose levels in the blood to drop and become lower. Glucagon is a hormone that is also released from your pancreas but this time in response to low levels of glucose in your blood. It causes the stored glycogen to be broken down back into glucose. It's then released into the bloodstream to raise blood glucose levels during times when you are not eating. For example when you are sleeping or in-between meals. When insulin levels are high, glucagon is not released. When glucagon levels are high then insulin levels are not released. The interplay between insulin and glucagon keeps your blood glucose constant between 90-100ml/dl throughout the day. When som Continue reading >>

How Insulin And Glucagon Work To Regulate Blood Sugar Levels

How Insulin And Glucagon Work To Regulate Blood Sugar Levels

The pancreas secretes insulin and glucagon, both of which play a vital role in regulating blood sugar levels. The two hormones work in balance. If the level of one hormone is outside the ideal range, blood sugar levels may spike or drop. Together, insulin and glucagon help keep conditions inside the body steady. When blood sugar is too high, the pancreas secretes more insulin. When blood sugar levels drop, the pancreas releases glucagon to bring them back up. Blood sugar and health The body converts carbohydrates from food into sugar (glucose), which serves as a vital source of energy. Blood sugar levels vary throughout the day but, in most instances, insulin and glucagon keep these levels normal. Health factors including insulin resistance, diabetes, and problems with diet can cause a person's blood sugar levels to soar or plummet. Blood sugar levels are measured in milligrams per decilitre (mg/dl). Ideal blood sugar ranges are as follows: Before breakfast - levels should be less than 100 mg/dl for a person without diabetes and 70-130 mg/dl for a person with diabetes. Two hours after meals - levels should be less than 140 mg/dl for a person without diabetes and less than 180 mg/dl for a person with diabetes. Blood sugar regulation Blood sugar levels are a measure of how effectively an individual's body uses glucose. When the body does not convert enough glucose for use, blood sugar levels remain high. Insulin helps the body's cells absorb glucose, lowering blood sugar and providing the cells with the glucose they need for energy. When blood sugar levels are too low, the pancreas releases glucagon. Glucagon forces the liver to release stored glucose, which causes the blood sugar to rise. Insulin and glucagon are both released by islet cells in the pancreas. These cells Continue reading >>

The Endocrine Pancreas

The Endocrine Pancreas

Cells and Secretions of the Pancreatic Islets The pancreatic islets each contain four varieties of cells: The alpha cell produces the hormone glucagon and makes up approximately 20 percent of each islet. Glucagon plays an important role in blood glucose regulation; low blood glucose levels stimulate its release. The beta cell produces the hormone insulin and makes up approximately 75 percent of each islet. Elevated blood glucose levels stimulate the release of insulin. The delta cell accounts for four percent of the islet cells and secretes the peptide hormone somatostatin. Recall that somatostatin is also released by the hypothalamus (as GHIH), and the stomach and intestines also secrete it. An inhibiting hormone, pancreatic somatostatin inhibits the release of both glucagon and insulin. The PP cell accounts for about one percent of islet cells and secretes the pancreatic polypeptide hormone. It is thought to play a role in appetite, as well as in the regulation of pancreatic exocrine and endocrine secretions. Pancreatic polypeptide released following a meal may reduce further food consumption; however, it is also released in response to fasting. Regulation of Blood Glucose Levels by Insulin and Glucagon Glucose is required for cellular respiration and is the preferred fuel for all body cells. The body derives glucose from the breakdown of the carbohydrate-containing foods and drinks we consume. Glucose not immediately taken up by cells for fuel can be stored by the liver and muscles as glycogen, or converted to triglycerides and stored in the adipose tissue. Hormones regulate both the storage and the utilization of glucose as required. Receptors located in the pancreas sense blood glucose levels, and subsequently the pancreatic cells secrete glucagon or insulin to mai Continue reading >>

What Is Glucagon?

What Is Glucagon?

Tweet The effects of glucagon are the opposite of the effects induced by insulin. The two hormones need to work in partnership with each other to keep blood glucose levels balanced. Glucagon is a hormone that is produced by alpha cells in a part of the pancreas known as the islets of Langerhans. The role of glucagon in the body Glucagon plays an active role in allowing the body to regulate the utilisation of glucose and fats. Glucagon is released in response to low blood glucose levels and to events whereby the body needs additional glucose, such as in response to vigorous exercise. When glucagon is released it can perform the following tasks: Stimulating the liver to break down glycogen to be released into the blood as glucose Activating gluconeogenesis, the conversion of amino acids into glucose Breaking down stored fat (triglycerides) into fatty acids for use as fuel by cells Glucagon and blood glucose levels Glucagon serves to keep blood glucose levels high enough for the body to function well. When blood glucose levels are low, glucagon is released and signals the liver to release glucose into the blood. Glucagon secretion in response to meals varies depending on what we eat: In response to a carbohydrate based meal, glucagon levels in the blood fall to prevent blood glucose rising too high. In response to a high protein meal, glucagon levels in the blood rise. Glucagon in diabetes In people with diabetes, glucagon’s presence can raise blood glucose levels too high. The reason for this is either because not enough insulin is present or, as is the case in type 2 diabetes, the body is less able to respond to insulin. In type 1 diabetes, high levels of circulating insulin can inhibit the release of glucagon in response to hypoglycemia. Medications which affect gluca Continue reading >>

How Diabetes Works

How Diabetes Works

Since diabetes is a disease that affects your body's ability to use glucose, let's start by looking at what glucose is and how your body controls it. Glucose is a simple sugar that provides energy to all of the cells in your body. The cells take in glucose from the blood and break it down for energy (some cells, like brain cells and red blood cells, rely solely on glucose for fuel). The glucose in the blood comes from the food that you eat. When you eat food, glucose gets absorbed from your intestines and distributed by the bloodstream to all of the cells in your body. Your body tries to keep a constant supply of glucose for your cells by maintaining a constant glucose concentration in your blood -- otherwise, your cells would have more than enough glucose right after a meal and starve in between meals and overnight. So, when you have an oversupply of glucose, your body stores the excess in the liver and muscles by making glycogen, long chains of glucose. When glucose is in short supply, your body mobilizes glucose from stored glycogen and/or stimulates you to eat food. The key is to maintain a constant blood-glucose level. To maintain a constant blood-glucose level, your body relies on two hormones produced in the pancreas that have opposite actions: insulin and glucagon. Insulin is made and secreted by the beta cells of the pancreatic islets, small islands of endocrine cells in the pancreas. Insulin is a protein hormone that contains 51 amino acids. Insulin is required by almost all of the body's cells, but its major targets are liver cells, fat cells and muscle cells. For these cells, insulin does the following: As such, insulin stores nutrients right after a meal by reducing the concentrations of glucose, fatty acids and amino acids in the bloodstream. See the next Continue reading >>

Glucose Metabolism And Regulation: Beyond Insulin And Glucagon

Glucose Metabolism And Regulation: Beyond Insulin And Glucagon

Insulin and glucagon are potent regulators of glucose metabolism. For decades, we have viewed diabetes from a bi-hormonal perspective of glucose regulation. This perspective is incomplete and inadequate in explaining some of the difficulties that patients and practitioners face when attempting to tightly control blood glucose concentrations. Intensively managing diabetes with insulin is fraught with frustration and risk. Despite our best efforts, glucose fluctuations are unpredictable, and hypoglycemia and weight gain are common. These challenges may be a result of deficiencies or abnormalities in other glucoregulatory hormones. New understanding of the roles of other pancreatic and incretin hormones has led to a multi-hormonal view of glucose homeostasis. HISTORICAL PERSPECTIVE Our understanding of diabetes as a metabolic disease has evolved significantly since the discovery of insulin in the 1920s. Insulin was identified as a potent hormonal regulator of both glucose appearance and disappearance in the circulation. Subsequently, diabetes was viewed as a mono-hormonal disorder characterized by absolute or relative insulin deficiency. Since its discovery, insulin has been the only available pharmacological treatment for patients with type 1 diabetes and a mainstay of therapy for patients with insulin-deficient type 2 diabetes.1–7 The recent discovery of additional hormones with glucoregulatory actions has expanded our understanding of how a variety of different hormones contribute to glucose homeostasis. In the 1950s, glucagon was characterized as a major stimulus of hepatic glucose production. This discovery led to a better understanding of the interplay between insulin and glucagon, thus leading to a bi-hormonal definition of diabetes. Subsequently, the discovery of Continue reading >>

Blood Glucose Regulation

Blood Glucose Regulation

Glucose is needed by cells for respiration. It is important that the concentration of glucose in the blood is maintained at a constant level. Insulin is a hormone produced by the pancreas that regulates glucose levels in the blood. How glucose is regulated Glucose level Effect on pancreas Effect on liver Effect on glucose level too high insulin secreted into the blood liver converts glucose into glycogen goes down too low insulin not secreted into the blood liver does not convert glucose into glycogen goes up Use the animation to make sure you understand how this works. You have an old or no version of flash - you need to upgrade to view this funky content! Go to the WebWise Flash install guide Glucagon – Higher tier The pancreas releases another hormone, glucagon, when the blood sugar levels fall. This causes the cells in the liver to turn glycogen back into glucose which can then be released into the blood. The blood sugar levels will then rise. Now try a Test Bite- Higher tier. Diabetes is a disorder in which the blood glucose levels remain too high. It can be treated by injecting insulin. The extra insulin allows the glucose to be taken up by the liver and other tissues, so cells get the glucose they need and blood-sugar levels stay normal. There are two types of diabetes. Type 1 diabetes Type 1 diabetes is caused by a lack of insulin. It can be controlled by: monitoring the diet injecting insulin People with type 1 diabetes have to monitor their blood sugar levels throughout the day as the level of physical activity and diet affect the amount of insulin required. Type 2 diabetes Type 2 diabetes is caused by a person becoming resistant to insulin. It can be controlled by diet and exercise. There is a link between rising levels of obesity (chronic overweight) and i Continue reading >>

What Is Glucagon?

What Is Glucagon?

Tweet The effects of glucagon are the opposite of the effects induced by insulin. The two hormones need to work in partnership with each other to keep blood glucose levels balanced. Glucagon is a hormone that is produced by alpha cells in a part of the pancreas known as the islets of Langerhans. The role of glucagon in the body Glucagon plays an active role in allowing the body to regulate the utilisation of glucose and fats. Glucagon is released in response to low blood glucose levels and to events whereby the body needs additional glucose, such as in response to vigorous exercise. When glucagon is released it can perform the following tasks: Stimulating the liver to break down glycogen to be released into the blood as glucose Activating gluconeogenesis, the conversion of amino acids into glucose Breaking down stored fat (triglycerides) into fatty acids for use as fuel by cells Glucagon and blood glucose levels Glucagon serves to keep blood glucose levels high enough for the body to function well. When blood glucose levels are low, glucagon is released and signals the liver to release glucose into the blood. Glucagon secretion in response to meals varies depending on what we eat: In response to a carbohydrate based meal, glucagon levels in the blood fall to prevent blood glucose rising too high. In response to a high protein meal, glucagon levels in the blood rise. Glucagon in diabetes In people with diabetes, glucagon’s presence can raise blood glucose levels too high. The reason for this is either because not enough insulin is present or, as is the case in type 2 diabetes, the body is less able to respond to insulin. In type 1 diabetes, high levels of circulating insulin can inhibit the release of glucagon in response to hypoglycemia. Medications which affect gluca Continue reading >>

Homeostasis Of Glucose Levels: Hormonal Control And Diabetes

Homeostasis Of Glucose Levels: Hormonal Control And Diabetes

Homeostasis According to the Centers for Disease Control and Prevention, there are almost 26 million people in the United States alone that have diabetes, which is 8.3% of the total U.S. population. With so many Americans suffering from diabetes, how do we treat all of them? Do all of these people now need insulin shots, or are there other ways to treat, or prevent, diabetes? In order to answer these questions, we must first understand the fundamentals of blood glucose regulation. As you may remember, homeostasis is the maintenance of a stable internal environment within an organism, and maintaining a stable internal environment in a human means having to carefully regulate many parameters, including glucose levels in the blood. There are two major ways that signals are sent throughout the body. The first is through nerves of the nervous system. Signals are sent as nerve impulses that travel through nerve cells, called neurons. These impulses are sent to other neurons, or specific target cells at a specific location of the body that the neuron extends to. Most of the signals that the human body uses to regulate body temperature are sent through the nervous system. The second way that signals can be sent throughout the body is through the circulatory system. These signals are transmitted by specific molecules called hormones, which are signaling molecules that travel through the circulatory system. In this lesson, we'll take a look at how the human body maintains blood glucose levels through the use of hormone signaling. Homeostasis of Blood Glucose Levels Glucose is the main source of fuel for the cells in our bodies, but it's too big to simply diffuse into the cells by itself. Instead, it needs to be transported into the cells. Insulin is a hormone produced by the panc Continue reading >>

Insulin And Glucagon

Insulin And Glucagon

Acrobat PDF file can be downloaded here. The islets of Langerhans The pancreatic Islets of Langerhans are the sites of production of insulin, glucagon and somatostatin. The figure below shows an immunofluorescence image in which antibodies specific for these hormones have been coupled to differing fluorescence markers. We can therefore identify those cells that produce each of these three peptide hormones. You can see that most of the tissue, around 80 %, is comprised of the insulin-secreting red-colored beta cells (ß-cells). The green cells are the α-cells (alpha cells) which produce glucagon. We see also some blue cells; these are the somatostatin secreting γ-cells (gamma cells). Note that all of these differing cells are in close proximity with one another. While they primarily produce hormones to be circulated in blood (endocrine effects), they also have marked paracrine effects. That is, the secretion products of each cell type exert actions on adjacent cells within the Islet. An Introduction to secretion of insulin and glucagon The nutrient-regulated control of the release of these hormones manages tissue metabolism and the blood levels of glucose, fatty acids, triglycerides and amino acids. They are responsible for homeostasis; the minute-to-minute regulation of the body's integrated metabolism and, thereby, stabilize our inner milieu. The mechanisms involved are extremely complex. Modern medical treatment of diabetes (rapidly becoming "public enemy number one") is based on insight into these mechanisms, some of which are not completely understood. I will attempt to give an introduction to this complicated biological picture in the following section. Somewhat deeper insight will come later. The Basics: secretion Let us begin with two extremely simplified figur Continue reading >>

Pancreas And Insulin

Pancreas And Insulin

Your pancreas is one of the organs of your digestive system. It lies in your abdomen, behind your stomach. It is a long thin structure with 2 main functions: producing digestive enzymes to break down food; and producing the hormones insulin and glucagon to control sugar levels in your body. Production of digestive enzymes The pancreas produces secretions necessary for you to digest food. The enzymes in these secretions allow your body to digest protein, fat and starch from your food. The enzymes are produced in the acinar cells which make up most of the pancreas. From the acinar cells the enzymes flow down various channels into the pancreatic duct and then out into the duodenum. The secretions are alkaline to balance the acidic juices and partially digested food coming into the duodenum from the stomach. Production of hormones to control blood sugar levels A small proportion (1-2 per cent) of the pancreas is made up of other types of cells called islets of Langerhans. These cells sit in tiny groups, like small islands, scattered throughout the tissue of the pancreas. The islets of Langerhans contain alpha cells which secrete glucagon and beta cells which secrete insulin. Insulin and glucagon are hormones that work to regulate the level of sugar (glucose) in the body to keep it within a healthy range. Unlike the acinar cells, the islets of Langerhans do not have ducts and secrete insulin and glucagon directly into the bloodstream. Depending on what you’ve eaten, how much exercise your muscles are doing, and how active your body cells are, the amount of glucose in your bloodstream and cells varies. These 2 hormones have the job of keeping tight control of the amount of glucose in your blood so that it doesn’t rise or fall outside of healthy limits. How insulin works I Continue reading >>

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