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Target Cells Of Insulin And Glucagon

Physiologic Effects Of Insulin

Physiologic Effects Of Insulin

Stand on a streetcorner and ask people if they know what insulin is, and many will reply, "Doesn't it have something to do with blood sugar?" Indeed, that is correct, but such a response is a bit like saying "Mozart? Wasn't he some kind of a musician?" Insulin is a key player in the control of intermediary metabolism, and the big picture is that it organizes the use of fuels for either storage or oxidation. Through these activities, insulin has profound effects on both carbohydrate and lipid metabolism, and significant influences on protein and mineral metabolism. Consequently, derangements in insulin signalling have widespread and devastating effects on many organs and tissues. The Insulin Receptor and Mechanism of Action Like the receptors for other protein hormones, the receptor for insulin is embedded in the plasma membrane. The insulin receptor is composed of two alpha subunits and two beta subunits linked by disulfide bonds. The alpha chains are entirely extracellular and house insulin binding domains, while the linked beta chains penetrate through the plasma membrane. The insulin receptor is a tyrosine kinase. In other words, it functions as an enzyme that transfers phosphate groups from ATP to tyrosine residues on intracellular target proteins. Binding of insulin to the alpha subunits causes the beta subunits to phosphorylate themselves (autophosphorylation), thus activating the catalytic activity of the receptor. The activated receptor then phosphorylates a number of intracellular proteins, which in turn alters their activity, thereby generating a biological response. Several intracellular proteins have been identified as phosphorylation substrates for the insulin receptor, the best-studied of which is insulin receptor substrate 1 or IRS-1. When IRS-1 is activa Continue reading >>

Normal Regulation Of Blood Glucose

Normal Regulation Of Blood Glucose

The human body wants blood glucose (blood sugar) maintained in a very narrow range. Insulin and glucagon are the hormones which make this happen. Both insulin and glucagon are secreted from the pancreas, and thus are referred to as pancreatic endocrine hormones. The picture on the left shows the intimate relationship both insulin and glucagon have to each other. Note that the pancreas serves as the central player in this scheme. It is the production of insulin and glucagon by the pancreas which ultimately determines if a patient has diabetes, hypoglycemia, or some other sugar problem. In this Article Insulin Basics: How Insulin Helps Control Blood Glucose Levels Insulin and glucagon are hormones secreted by islet cells within the pancreas. They are both secreted in response to blood sugar levels, but in opposite fashion! Insulin is normally secreted by the beta cells (a type of islet cell) of the pancreas. The stimulus for insulin secretion is a HIGH blood glucose...it's as simple as that! Although there is always a low level of insulin secreted by the pancreas, the amount secreted into the blood increases as the blood glucose rises. Similarly, as blood glucose falls, the amount of insulin secreted by the pancreatic islets goes down. As can be seen in the picture, insulin has an effect on a number of cells, including muscle, red blood cells, and fat cells. In response to insulin, these cells absorb glucose out of the blood, having the net effect of lowering the high blood glucose levels into the normal range. Glucagon is secreted by the alpha cells of the pancreatic islets in much the same manner as insulin...except in the opposite direction. If blood glucose is high, then no glucagon is secreted. When blood glucose goes LOW, however, (such as between meals, and during Continue reading >>

Pancreatic Regulation Of Glucose Homeostasis

Pancreatic Regulation Of Glucose Homeostasis

Go to: The pancreas is an exocrine and endocrine organ The pancreas has key roles in the regulation of macronutrient digestion and hence metabolism/energy homeostasis by releasing various digestive enzymes and pancreatic hormones. It is located behind the stomach within the left upper abdominal cavity and is partitioned into head, body and tail. The majority of this secretory organ consists of acinar—or exocrine—cells that secrete the pancreatic juice containing digestive enzymes, such as amylase, pancreatic lipase and trypsinogen, into the ducts, that is, the main pancreatic and the accessory pancreatic duct. In contrast, pancreatic hormones are released in an endocrine manner, that is, direct secretion into the blood stream. The endocrine cells are clustered together, thereby forming the so-called islets of Langerhans, which are small, island-like structures within the exocrine pancreatic tissue that account for only 1–2% of the entire organ (Figure 1).1 There are five different cell types releasing various hormones from the endocrine system: glucagon-producing α-cells,2 which represent 15–20% of the total islet cells; amylin-, C-peptide- and insulin-producing β-cells,2 which account for 65–80% of the total cells; pancreatic polypeptide (PP)-producing γ-cells,3 which comprise 3–5% of the total islet cells; somatostatin-producing δ-cells,2 which constitute 3–10% of the total cells; and ghrelin-producing ɛ-cells,4 which comprise <1% of the total islet cells. Each of the hormones has distinct functions. Glucagon increases blood glucose levels, whereas insulin decreases them.5 Somatostatin inhibits both, glucagon and insulin release,6 whereas PP regulates the exocrine and endocrine secretion activity of the pancreas.3, 7 Altogether, these hormones regul Continue reading >>

C2006/f2402 '11 Outline Of Lecture #16

C2006/f2402 '11 Outline Of Lecture #16

Handouts: 15A -- Lining of the GI Tract & Typical Circuit 15B -- Homeostasis -- Seesaw view for Glucose and Temperature Regulation; 16 -- Absorptive vs Postabsorptive state I. Homeostasis, cont. See handouts 15A & B & notes of last time, topic VI. A. Regulation of Blood Glucose Levels -- Seesaw View #1 (Handout 15B) B. Regulation of Human Body Temperature -- Seesaw #2 (Handout 15B) C. The Circuit View (Handout 15A) II. Matching circuits and signaling -- an example: How the glucose circuit works at molecular/signaling level Re-consider the circuit or seesaw diagram for homeostatic control of blood glucose levels -- what happens in the boxes on 15A? It may help to refer to the table below. A. How do Effectors Take Up Glucose? 1. Major Effectors: Liver, skeletal muscle, adipose tissue 2. Overall: In response to insulin, effectors increase both uptake & utilization of glucose. Insulin triggers one or more of the following in the effectors: a. Causes direct increase of glucose uptake by membrane transporters b. Increases breakdown of glucose to provide energy c. Increases conversion of glucose to 'stores' (1). Glucose is converted to storage forms (fat, glycogen), AND (2). Breakdown of storage fuel molecules (stores) is inhibited. d. Causes indirect increase of glucose uptake by increasing phosphorylation of glucose to G-P, trapping it inside cells 3. How does Insulin Work? a. Receptor: (1). Insulin works through a special type of cell surface receptor, a tyrosine kinase linked receptor; See Sadava fig. 7.7 (15.6). Insulin has many affects on cells and the mechanism of signal transduction is complex (activating multiple pathways). (2). In many ways, insulin acts more like a typical growth factor than like a typical endocrine. (Insulin has GF-like effects on other cells; is i Continue reading >>

Histologic Distribution Of Insulin And Glucagon Receptors

Histologic Distribution Of Insulin And Glucagon Receptors

M. Watanabe, H. Hayasaki, T. Tamayama and M. Shimada Department of Anatomy, Osaka Medical College, Takatsuki, Osaka, Japan Insulin and glucagon are the hormonal polypeptides secreted by the B and A cells of the endocrine pancreas, respectively. Their major physiologic effects are regulation of carbohydrate metabolism, but they have opposite effects. Insulin and glucagon have various physiologic roles, in addition to the regulation of carbohydrate metabolism. The physiologic effects of insulin and glucagon on the cell are initiated by the binding of each hormone to receptors on the target cells. Morphologic studies may be useful for relating biochemical, physiologic, and pharmacologic information on the receptors to an anatomic background. Receptor radioautography techniques using radioligands to label specific insulin and glucagon receptors have been successfully applied to many tissues and organs. In this review, current knowledge of the histologic distribution of insulin and glucagon receptors is presented with a brief description of receptor radioautography techniques. Key words: radioautography, insulin, glucagon, receptor, distribution Introduction Insulin is a hormone secreted by B cells, and glucagon is secreted by A cells of the pancreas. The two hormones play an important role in carbohydrate metabolism. However, the actions of insulin and glucagon in carbohydrate metabolism are opposite. Furthermore, insulin and glucagon have various physiologic roles in addition to the regulation of carbohydrate metabolism. The physiologic effects of insulin and glucagon on the cell are initiated by the binding of each hormone to target cell receptors. To relate biochemical, physiologic, and pharmacologic information on receptors to an anatomic background, morphologic studies Continue reading >>

What Are The Target Cells For Insulin And Glucagon?

What Are The Target Cells For Insulin And Glucagon?

What are the target cells for insulin AND glucagon? Insulin targets all cells that have accumulated glucose right? What about glucagon? Are you sure you want to delete this answer? Best Answer: Glucagon is one of the many hormones that act through activation of adenyl cyclase, increasing the level of cyclic AMP in target cells. Glucagon receptors are found primarily in adipose tissue (where the hormone initials lipolysis and release of fatty acids) and the liver (where it promotes glucose release through activation of glycogenolysis and gluconeogenesis). Skeletal muscle does not have receptors for this hormone. Insulin stimulates glucose uptake in the liver, fat cells and skeletal muscle. liver produces glucagon which converts glycogen into glucose (opposite effect of insulin) which raises the blood level sugar. I think this question violates the Community Guidelines Chat or rant, adult content, spam, insulting other members, show more I think this question violates the Terms of Service Harm to minors, violence or threats, harassment or privacy invasion, impersonation or misrepresentation, fraud or phishing, show more If you believe your intellectual property has been infringed and would like to file a complaint, please see our Copyright/IP Policy I think this answer violates the Community Guidelines Chat or rant, adult content, spam, insulting other members, show more I think this answer violates the Terms of Service Harm to minors, violence or threats, harassment or privacy invasion, impersonation or misrepresentation, fraud or phishing, show more If you believe your intellectual property has been infringed and would like to file a complaint, please see our Copyright/IP Policy I think this comment violates the Community Guidelines Chat or rant, adult content, spam, i Continue reading >>

Glucagon

Glucagon

This article is about the natural hormone. For the medication, see Glucagon (medication). Glucagon is a peptide hormone, produced by alpha cells of the pancreas. It works to raise the concentration of glucose and fat in the bloodstream, and is considered to be the main catabolic hormone of the body [3]. It is also used as a medication to treat a number of health conditions. Its effect is opposite to that of insulin, which lowers the extracellular glucose.[4] The pancreas releases glucagon when the concentration of glucose in the bloodstream falls too low. Glucagon causes the liver to convert stored glycogen into glucose, which is released into the bloodstream.[5] High blood-glucose levels, on the other hand, stimulate the release of insulin. Insulin allows glucose to be taken up and used by insulin-dependent tissues. Thus, glucagon and insulin are part of a feedback system that keeps blood glucose levels stable. Glucagon increases energy expenditure and is elevated under conditions of stress.[6] Glucagon belongs to the secritin family of hormones. Function[edit] Glucagon generally elevates the concentration of glucose in the blood by promoting gluconeogenesis and glycogenolysis [7]. Glucagon also decreases fatty acid synthesis in adipose tissue and the liver, as well as promoting lipolysis in these tissues, which causes them to release fatty acids into circulation where they can be catabolised to generate energy in tissues such as skeletal muscle when required [8]. Glucose is stored in the liver in the form of the polysaccharide glycogen, which is a glucan (a polymer made up of glucose molecules). Liver cells (hepatocytes) have glucagon receptors. When glucagon binds to the glucagon receptors, the liver cells convert the glycogen into individual glucose molecules and re 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 >>

Regulation Of Insulin And Glucagon Secretion

Regulation Of Insulin And Glucagon Secretion

Insulin and glucagon secretion is largely regulated by the plasma concentrations of glucose and, to a lesser degree, of amino acids. The alpha and beta cells, therefore, act as both the sensors and effectors in this control system. Since the plasma concentration of glucose and amino acids rises during the absorption of a meal and falls during fasting, the secretion of insulin and glucagon likewise fluctuates between the absorptive and postabsorptive states. These changes in insulin and gluca-gon secretion, in turn, cause changes in plasma glucose and amino acid concentrations and thus help to maintain homeosta-sis via negative feedback loops (fig. 19.6). As described in chapter 6, insulin stimulates the insertion of GLUT4 channels into the plasma membrane (due to the fusion of intracellular vesicles with the plasma membrane—see fig. 6.15) of its target cells, primarily in the skeletal and cardiac muscles, adipose tissue, and liver. This permits the entry of glucose into its target cells by facilitated diffusion. As a result, in- ■ Figure 19.6 The regulation of insulin and glucagon secretion. The secretion from the P (beta) cells and a (alpha) cells of the pancreatic islets is regulated largely by the blood glucose concentration. (a) A high blood glucose concentration stimulates insulin and inhibits glucagon secretion. (b) A low blood glucose concentration stimulates glucagon and inhibits insulin secretion. sulin promotes the production of the energy-storage molecules of glycogen and fat. Both actions decrease the plasma glucose concentration. Insulin also inhibits the breakdown of fat, induces the production of fat-forming enzymes, and inhibits the breakdown of muscle proteins. Thus, insulin promotes an-abolism as it regulates the blood glucose concentration. The me Continue reading >>

17.9 The Pancreas | Anatomy & Physiology

17.9 The Pancreas | Anatomy & Physiology

By the end of this section, you will be able to: Explain the role of the pancreatic endocrine cells in the regulation of blood glucose Describe the location and structure of the pancreas, and the morphology and function of the pancreatic islets Compare and contrast the function and regulation of insulin and glucagon The pancreas is a long, slender organ, most of which is located posterior to the bottom half of the stomach ( Figure 1 ). Although it is primarily an exocrine gland, secreting a variety of digestive enzymes, the pancreas also has endocrine cells. Its pancreatic isletsclusters of cells formerly known as the islets of Langerhanssecrete the hormones glucagon, insulin, somatostatin, and pancreatic polypeptide (PP). Figure 1. Pancreas endocrine function involves the secretion of insulin (produced by beta cells) and glucagon (produced by alpha cells) within the pancreatic islets. These two hormones regulate the rate of glucose metabolism in the body. The micrograph reveals pancreatic islets. LM 760. Also shown are the exocrine acinar cells. (Micrograph provided by the Regents of University of Michigan Medical School 2012) View the University of Michigan WebScope at to explore the tissue sample in greater detail. 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. Low blood glucose levels stimulate the release of glucagon. 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 al 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 >>

Insulin And Glucagon From The Pancreas

Insulin And Glucagon From The Pancreas

Sort Insulin and Glucagon from the Pancreas Endocrine function: Secretes hormones that enter the blood Islets of Langerhans 2-3% of the pancreas by weight Islets are vascularized, innervated; have four basic cell types: A cells B cells D cells F cells Insulin and Glucagon from the Pancreas: different cell types A cells: Make Glucagon Are about 20% of Islet cells Surround -cells B cells: = -cells Make Insulin 60-75% of Islet cells D cells: Make Somatostatin Are 3-5% of Islet cells F cells: Make Pancreatic Polypeptide Are found in one end lobe of the pancreas where they are the predominant cell type in the Islets Insulin - the first protein sequenced: Sanger, F., 1945 The free amino groups of insulin. Biochem. J. 39: 507-515 Sanger, F., 1949 The terminal peptides of insulin. Biochem. J. 45: 563-574 Sanger, F., and H. Tuppy, 1951a The amino-acid sequence in the phenylalanyl chain of insulin. 1. The identification of lower peptides from partial hydrolysates. Biochem. J. 49: 463-481 Sanger, F., and H. Tuppy, 1951b The amino-acid sequence in the phenylalanyl chain of insulin. 2. The investigation of peptides from enzymic hydrolysates. Biochem. J. 49: 481-490 Sanger, F., and E. O. P. Thompson, 1953a The amino-acid sequence in the glycyl chain of insulin. 1. The investigation of lower peptides from partial hydrolysates. Biochem. J. 53: 353-366 Sanger, F., and E. O. P. Thompson, 1953b The amino-acid sequence in the glycyl chain of insulin. 2. The investigation of peptides from enzymic hydrolysates. Biochem. J. 53: 366-374 Ryle, A. P., F. Sanger, L. F. Smith and R. Kitai, 1955 The disulphide bonds of insulin. Biochem. J. 60: 542-556 "It has frequently been suggested that proteins may not be pure chemical entities but may consist of mixtures of closely related substances with no a Continue reading >>

Histologic Distribution Of Insulin And Glucagon Receptors.

Histologic Distribution Of Insulin And Glucagon Receptors.

Histologic distribution of insulin and glucagon receptors. Department of Anatomy, Osaka Medical College, Japan. [email protected] Insulin and glucagon are the hormonal polypeptides secreted by the B and A cells of the endocrine pancreas, respectively. Their major physiologic effects are regulation of carbohydrate metabolism, but they have opposite effects. Insulin and glucagon have various physiologic roles, in addition to the regulation of carbohydrate metabolism. The physiologic effects of insulin and glucagon on the cell are initiated by the binding of each hormone to receptors on the target cells. Morphologic studies may be useful for relating biochemical, physiologic, and pharmacologic information on the receptors to an anatomic background. Receptor radioautography techniques using radioligands to label specific insulin and glucagon receptors have been successfully applied to many tissues and organs. In this review, current knowledge of the histologic distribution of insulin and glucagon receptors is presented with a brief description of receptor radioautography techniques. Continue reading >>

Insulin And Glucagon

Insulin And Glucagon

Transcript of Insulin and Glucagon Insulin and Glucagon Introduction The Functions of Insulin and Glucagon and their contribution to Homeostasis Both Glucagon and Insulin maintain the balance of blood glucose levels in our bodies. Glucose provides fuel and energy for our body. Insulin helps the glucose in the blood to enter in the cells. Without the role of Insulin, our body cells can not take up the glucose from the blood, causing difficulties to perform tasks. When there is a shortage of glucose, alpha cells release glucagon. The target organs/structures of the hormone Insulin is secreted by the beta cells of the pancreas mostly when there is high blood sugar. After a meal, the total amount of insulin secreted by the pancreas increases along with the blood glucose. When the blood glucose decreases, the amount of insulin secreted by the pancreas also decreases. The pancreus detects the amount of glucose in the blood by its cells which release insulin when it is too high and release glucagon when it is too low. Insulin and Glucagon Production Insulin is made in the pancreas. It is produced by beta cells in the langerhans(groups of pancreatic cells that maintain normal levels of blood sugar). Insulin takes the sugar from food we consume into cells so we can use that sugar for energy. Glucagon is produced by alpha cells also found in the pancreas. Regulation and Control of Insulin Regulation and Control of Glucagon Noah Golub, Sapir Meoded, Megan Horwitz, and Michal Chetrit The pancreas is an organ found behind the stomach, in the back of the abdomen. It is part of the digestive and endocrine systems. It has multiple different jobs, one is to secrete digestive enzyme juices for the digestive system and the other is to produce insulin, glucagon and other hormones for the b Continue reading >>

What Are The Target Cells Of Insulin And Glucagon?

What Are The Target Cells Of Insulin And Glucagon?

Science Human Anatomy The liver contains glucagon receptors. When stimulated by glucagon, these receptors enable glucose release through the activation of glycogenolysis and gluconeogenesis. These processes activate adenal cyclase, which raises cyclic adenosine monophosphate in target cells. When affected by insulin, liver cells are stimulated to conduct glucose uptake. Insulin binds to the target cells and allows the cell to pull glucose in through its membranes via signal transduction. The glucose is then used as an energy source for the cell. Learn more about Human Anatomy Continue reading >>

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