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Target Cells Of Insulin And Glucagon

Blood Sugar Regulation

Blood Sugar Regulation

Most cells in the human body use the sugar called glucose as their major source of energy. Glucose molecules are broken down within cells in order to produce adenosine triphosphate (ATP) molecules, energy-rich molecules that power numerous cellular processes. Glucose molecules are delivered to cells by the circulating blood and therefore, to ensure a constant supply of glucose to cells, it is essential that blood glucose levels be maintained at relatively constant levels. Level constancy is accomplished primarily through negative feedback systems, which ensure that blood glucose concentration is maintained within the normal range of 70 to 110 milligrams (0.0024 to 0.0038 ounces) of glucose per deciliter (approximately one-fifth of a pint) of blood. Negative feedback systems are processes that sense changes in the body and activate mechanisms that reverse the changes in order to restore conditions to their normal levels. Negative feedback systems are critically important in homeostasis, the maintenance of relatively constant internal conditions. Disruptions in homeostasis lead to potentially life-threatening situations. The maintenance of relatively constant blood glucose levels is essential for the health of cells and thus the health of the entire body. Major factors that can increase blood glucose levels include glucose absorption by the small intestine (after ingesting a meal) and the production of new glucose molecules by liver cells. Major factors that can decrease blood glucose levels include the transport of glucose into cells (for use as a source of energy or to be stored for future use) and the loss of glucose in urine (an abnormal event that occurs in diabetes mellitus). Insulin and Glucagon In a healthy person, blood glucose levels are restored to normal level Continue reading >>

How Insulin And Glucagon Work

How Insulin And Glucagon Work

Insulin and glucagon are hormones that help regulate the levels of blood glucose, or sugar, in your body. Glucose, which comes from the food you eat, moves through your bloodstream to help fuel your body. Insulin and glucagon work together to balance your blood sugar levels, keeping them in the narrow range that your body requires. These hormones are like the yin and yang of blood glucose maintenance. Read on to learn more about how they function and what can happen when they don’t work well. Insulin and glucagon work in what’s called a negative feedback loop. During this process, one event triggers another, which triggers another, and so on, to keep your blood sugar levels balanced. How insulin works During digestion, foods that contain carbohydrates are converted into glucose. Most of this glucose is sent into your bloodstream, causing a rise in blood glucose levels. This increase in blood glucose signals your pancreas to produce insulin. The insulin tells cells throughout your body to take in glucose from your bloodstream. As the glucose moves into your cells, your blood glucose levels go down. Some cells use the glucose as energy. Other cells, such as in your liver and muscles, store any excess glucose as a substance called glycogen. Your body uses glycogen for fuel between meals. Read more: Simple vs. complex carbs » How glucagon works Glucagon works to counterbalance the actions of insulin. About four to six hours after you eat, the glucose levels in your blood decrease, triggering your pancreas to produce glucagon. This hormone signals your liver and muscle cells to change the stored glycogen back into glucose. These cells then release the glucose into your bloodstream so your other cells can use it for energy. This whole feedback loop with insulin and gluca 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 >>

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 >>

Bbc Bitesize - National 5 Biology - Control And Communication - Revision 4

Bbc Bitesize - National 5 Biology - Control And Communication - Revision 4

Communication between cells in a multicellular organism occurs by use of nerve impulses or hormones. The central nervous system produces electrical impulses for rapid response. Hormones are chemical messengers. Hormones are released into the bloodstream by groups of cells called endocrine glands . Hormones are transported in the blood plasma to target body tissues where they bind to cells to produce a response. A specific hormone can only affect cells if the cells have a receptor for it. The diagram below shows two cells targeted by two different hormones. Hormone one cannot affect the cell on the right because the cell does not have a receptor for it. The concentration of glucose in the blood must be kept at a set point. If the blood glucose concentration rises too high then the water concentration of the blood will fall and water will diffuse out of cells by osmosis. This may interfere with cell reactions. If the blood glucose concentration falls too much, then body cells will not receive as much glucose and so will not be able to release as much energy in respiration. The concentration of glucose in the blood is regulated by the action of the hormones insulin 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 >>

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 >>

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 >>

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 >>

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 >>

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 >>

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 >>

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 >>

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 >>

Is Liver A Primary Target For Insulin Action?

Is Liver A Primary Target For Insulin Action?

I am looking into the possible causes of metabolic syndrome. I have noticed on the web that some people consider a liver to be a primary target for the action of insulin, and as such, when it becomes insulin resistant, it can cause disruption in the glucose homeostasis in the whole body - in contrary with the traditional adipocentric view, by which it is the accumulation of excess fat that leads to inflammation and a whole cascade of biochemical and physiological events. Can insulin resistant liver produce enough glucose via gluconeogenesis to cause hyperinsulinemia and hyperglycemia in humans? I have read some studies, they did this in mice, dogs, humans... they reported hyperglycemia and hyperinsulinemia, but is this the same as in hyperinsulinemic people? Glucagon has been told to mediate gluconeogenesis. It cannot act on the tissues when insulin levels are high, but the lack of insulin mediation due to insulin resistant tissues, this can lead to gluconeogenesis. To what extend - in comparison to the action of glucagon? I have also read that in the portal vein there can be three times higher insulin concentration than in the systemic circulation. Is the regulation of insulin concentrations in these two compartments dependent on the pancreas, or how do these differ? When liver becomes insulin resistant, is it blind to the insulin in the portal vein as well? I personally believe that it is mainly the muscles that determine whether a person will become hyperglycemic and hyperinsulinemic, because these are the biggest organ that needs insulin to take glucose in on the every day basis. When people remain bed bound or physically inactive and overeat, the glucose and fat content of the muscles is mostly full and cannot take in anymore. Liver glycogen is also easily replenis Continue reading >>

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