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How Does Homeostasis Control Blood Sugar Levels?

The Pancreas, Insulin And Glucagon Fact Sheet

The Pancreas, Insulin And Glucagon Fact Sheet

HOMEOSTASIS The Pancreas, Insulin and Glucagon Fact Sheet Insulin and Glucagon INSULIN GLUCAGON A protein made of two short polypeptide chains linked by disulphide bridges. It is synthesised at the ribosome as a single polypeptide (proinsulin) and is later activated by enzymatic cleavage into the two chains. A small protein made up of 29 amino acids. It is made by the alpha cells in the Islets. It is also made in an inactive form proglucagon before it is released. Action of Insulin Action of Glucagon Increases the entry of glucose into the body cells. Notable exceptions being brain tissue, red blood cells, kidney tubule. and intestinal lining. Inhibits glycogen breakdown in liver and muscle. Glucagon binds to liver cells, stimulating the breakdown of glycogen into glucose. It does not affect glycogen in muscle tissue. Inhibits lipid breakdown in liver and adipose tissue. Increases lipid breakdown though its influence is small. Increases the uptake of amino acids by cells and increases the rate of protein synthesis (here it is acting as a growth hormone) Stimulates the formation of glucose from amino acids in the liver. The action of insulin is very rapid, so is its breakdown (t½ = 10 to 25 min). Once released into the blood stream insulin binds with the receptor sites on its target cells' plasma membrane. This stimulates vesicles carrying glucose pores which lie in the cytoplasm of these cells, to fuse with the plasma membrane. Insulin is broken down by enzyme action in many tissues. Glucagon is also very short lived (t½ = 5 to 10 min). Glucagon is broken down particularly by the liver tissue. As the hormone is secreted into the blood flowing into the liver little glucagon is seen circulating in the rest of the body. Control of Insulin Secretion Control of Glucagon Se Continue reading >>

Homeostasis

Homeostasis

Homeostasis is the maintenance of a constant internal environment of a cell or an organism, despite fluctuations in the external environment. It has evolved because it gives some organisms a survival advantage. Maintaining a constant body temperature, where enzyme activity is at its optimum level, enables animals to hunt even in freezing conditions. Homeostasis is therefore energy consuming. Some animals prefer not to waste energy maintaining body systems constantly at the ready and reduce their level of activity during cold months by hibernating, such as bears, or remaining dormant as in the case of insects. Homeostasis works by way of feedback mechanisms. Examples include the maintenance of the blood at a specific pH range and body temperature. Systems such as the urinary and respiratory systems work in isolation or in concert to maintain homeostasis. Feedback mechanisms involve: - Receptors in the body that pick up specific changes. this may include heat or blood glucose levels. - A control centre, in most cases it is the brain, that regulates the response. - Effectors, muscles or organs, that are stimulated to cause an effect that corrects the deviation in the internal conditions. The effectors are stimulated until the response has returned the body back to a state of balance and the receptors are no longer active. Two types of feedback mechanisms exist, negative and positive feedback. Negative feedback acts in such a way as to reverse the change that has occurred, while a positive feedback acts to enhance the change that has taken place. In fact most of the life sustaining processes in our body operate on negative feedback. One example of negative feedback is maintenance of the blood glucose level. Click to see the video on the right. Insulin is a hormone,like all Continue reading >>

Brain May Play Key Role In Blood Sugar Metabolism And Diabetes Development

Brain May Play Key Role In Blood Sugar Metabolism And Diabetes Development

A growing body of evidence suggests that the brain plays a key role in glucose regulation and the development of type 2 diabetes, researchers write in the Nov. 7 ssue of the journal Nature. If the hypothesis is correct, it may open the door to entirely new ways to prevent and treat this disease, which is projected to affect one in three adults in the United States by 2050. In the paper, lead author Dr. Michael W. Schwartz, UW professor of medicine and director of the Diabetes and Obesity Center of Excellence, and his colleagues from the universities of Cincinnati, Michigan, and Munich, note that the brain was originally thought to play an important role in maintaining normal glucose metabolism With the discovery of insulin in the 1920s, the focus of research and diabetes care shifted to almost exclusively to insulin. Today, almost all treatments for diabetes seek to either increase insulin levels or increase the body’s sensitivity to insulin. “These drugs,” the researchers write, “enjoy wide use and are effective in controlling hyperglycemia [high blood sugar levels], the hallmark of type 2 diabetes, but they address the consequence of diabetes more than the underlying causes, and thus control rather than cure the disease.” New research, they write, suggests that normal glucose regulation depends on a partnership between the insulin-producing cells of the pancreas, the pancreatic islet cells, and neuronal circuits in the hypothalamus and other brain areas that are intimately involved in maintaining normal glucose levels. The development of diabetes type 2, the authors argue, requires a failure of both the islet-cell system and this brain-centered system for regulating blood sugar levels . In their paper, the researchers review both animal and human studies tha Continue reading >>

Homeostatic Mechanisms Function To Maintain The Body In A State Of Equilibrium And Allow A Degree Of Independence From The Environment

Homeostatic Mechanisms Function To Maintain The Body In A State Of Equilibrium And Allow A Degree Of Independence From The Environment

BYA7 SECTION 16.11 Homeostatic mechanisms function to maintain the body in a state of equilibrium and allow a degree of independence from the environment Principles of Homeostasis EXCESS NORM DEFICIENCY Change detected by β-cells in pancreas Change detected by α-cells in pancreas Increase in insulin secretion - Activates enzymes converting glucose to glycogen - Increases rate of glucose uptake Increase in glucagon secretion - Activates enzymes converting glycogen to glucose Levels return to norm Levels return to norm Features that influence internal environment have a set level → norm Negative feedback / caused by deviation from norm / change results in return to norm External environment is changing → experienced by body Homeostatic system even out variations experienced by body Liver can store or release glucose Blood is kept at a constant, ideal state Tissue fluid surrounds working cell with constant ideal conditions Optimum glucose for respiration Homeostasis is achieved by a negative feedback and involves Change in level of an internal factor (change from norm level) Detected by receptors / impulse send to hypothalamus Level of factor returns to norm Factors in blood and tissue fluid must be kept constant: Temp and pH Change affects rate of enzyme-controlled/biochemical reactions Extreme changes denatures proteins Humans maintain constant core body temp between 36-37.8°C Body temp refers to core body temp → limbs may be cooler than 37°C Water potential / avoids osmotic problems → cellular disruption Conc of ions (Na, K, Ca) Blood flows through receptors in the hypothalamus Deviation causes the autonomic nervous system to initiate an appropriate response Receptors in hypothalamus detect increase in core temp/temp of blood Heat conversation centre stimula Continue reading >>

Negative Feedback And Blood Glucose Regulation

Negative Feedback And Blood Glucose Regulation

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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 >>

Homeostasis - Glucose Regulation, Thermoregulation, And The Excretory System

Homeostasis - Glucose Regulation, Thermoregulation, And The Excretory System

Sort How can organisms regulate their body temperature behaviourally? - Burrowing in the soil - Laying out in the sun (reptiles may lay on a rock) - "sunning" - Fan ourselves - Clothing - Seek shelter - Wallowing in the mud - Lying in water - Finding shade Diabetes I and II - Type 1 Diabetes : (pretty rare) - sometimes known as "juvenile" diabetes because it adheres in your childhood, the cause is autoimmune. The body's immune system mistakenly attacks and kills beta and/or alpha cells (which make insulin and glucagon) from the pancreas, this results in the person not making enough insulin and or glucagon and therefore they CANNOT REGULATE THEIR BLOOD SUGAR ON THEIR OWN, a treatment is insulin injections. If their blood sugar is high, they will need insulin injections so that the sugar can go to the CELLS, if they have low blood sugar they can eat a snack. - Type 2 Diabetes: due to eating a lot of processed food, the person with this type doesn't usually have problems creating insulin (binds to receptor cells and protein that is attached to the receptor changes its shape, and sugar is allowed to enter the cell, the transporter that usually allows the sugar in doesn't allow it into the cell which is why their blood sugar level is too high and causes diabetes), but has a problem with regulating blood sugar level. If blood sugar level stays high for long periods of time or spikes rapidly, then INSULIN NO LONGER TAKES IN GLUCOSE - High blood sugar level is caused by overeating, spikes of high blood sugar levels is caused by eating too much sugar at once. - Increased fiber intake of meals helps to slow the absorption of glucose into the bloodstream. - Exercising breaks down sugar in the blood and breaks down glycogen which also helps regulate blood sugar. Which organs are in Continue reading >>

Controlling Blood Sugar Level

Controlling Blood Sugar Level

Diabetes Glucose is a sugar needed by cells for respiration. It is important that the concentration of glucose in the blood is maintained at a constant level. Insulin, a hormone secreted by the pancreas, controls blood sugar levels in the body. Diabetes is a disorder in which the blood glucose levels remain too high. It can be treated by carefully maintaining a certain diet or 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. Higher only What happens when glucose levels in the blood become too high or too low 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 Menstrual cycle The menstrual cycle in women is a recurring process in which the lining of the uterus is prepared for pregnancy. If pregnancy does not happen, the lining is shed at menstruation. Several hormones control this cycle: oestrogen, which causes the repair of the uterus wall progesterone, which maintains the uterus wall Both hormones are secreted by the ovaries. The image below shows how the levels of oestrogen and progesterone change during the menstrual cycle. If a woman becomes pregnant, the level of progesterone remains high. Controlling fertility Human fertility is controlled by hormones. This means that a knowledge of hormones can be used to decide to increase, or reduce, the chances of fe Continue reading >>

Homeostatic Control Of Blood Glucose Levels Essay

Homeostatic Control Of Blood Glucose Levels Essay

Homeostatic Control of Blood Glucose Levels Glucose is an essential substance in the body as it is the primary source of energy for all biological functions and is indeed the only form of energy which can be used by the brain and central nervous system. The ideal level of blood glucose is 80 - 90mg of glucose per 100mls of blood. However this level is not static - it oscillates due to changes in the body which are brought about by actions such as eating a meal, exercising, or not eating for long periods. If blood glucose levels drop or rise dramatically there may be serious consequences such as hypo- or hyperglycaemia which can both cause death. Thus it is necessary for blood glucose levels to be …show more content… The level of blood glucose is constantly monitored by the beta cells. As the effects of insulin bring down the blood glucose level the cells secrete less and less of the hormone in accordance with the falling level of blood glucose - this continues until levels return to normal. The corresponding effect of this antagonistic mechanism occurs when blood glucose level have fallen too low - this is detected in the Islets of Langerhans by the alpha cells which are stimulated to produce glucagon. This hormone acts in two main ways to raise blood glucose concentration back to normal levels. Firstly, it stimulates the process of glycogenolysis whereby the liver and muscle cells convert glycogen into glucose to be discharged into the blood. In addition, it increases gluconeogenesis so that more glucose is synthesised from protein and fat sources. However if glucagon is allowed to encourage the production of glucose unchecked, the liver will begin to produce ketones which dangerously disrupt the acid/base balance in the body. The two… Continue reading >>

What Happens To Blood Sugar Levels During Exercise?

What Happens To Blood Sugar Levels During Exercise?

Muscles hold enough energy stores for a short burst of activity. After that, they depend on increased blood supply to deliver oxygen, blood sugar and other nutrients to manufacture more energy. Your body burns the sugar in your blood, and then calls for your liver to supply stored glucose to keep up with energy demands. This causes fluctuations in your blood sugar when you exercise. Video of the Day As you warm up, your muscles start to call for nutrients to manufacture energy. Glucose carried in your blood and delivered to the muscles is an energy supply, as are free fatty acids, a type of lipid carried in blood that provide energy when glucose is low. Using energy during exercise helps balance high blood sugar and provide fuel at the same time. As blood flow to your muscles increases, the energy supplies increase as well. Your muscle cells send signals to start burning glucose, and more of it is delivered to the cells. This lowers your blood sugar levels. Sugars from the foods you eat are stored in your liver and in other tissues in a form called glycogen. When your body requires more sugar than is available in your blood, it starts to convert stored sugars to a usable form, releasing them into the blood. Blood sugar levels in your blood increase as muscles and oter tissues call for release of energy into your bloodstream. When glycogen provides fuel for your muscles, your blood sugar fluctuates up and down as it's used. Elevated Blood Sugar If your blood sugar is high when you begin to exercise, it can climb higher. This is because your body does not recognize the glucose in your blood, and calls for your liver to break down more glycogen. If your blood sugar is high before exercise, you should wait until it is within normal range before you exercise, according to Jo Continue reading >>

Blood Sugar Regulation

Blood Sugar Regulation

Ball-and-stick model of a glucose molecule Blood sugar regulation is the process by which the levels of blood sugar, primarily glucose, are maintained by the body within a narrow range. This tight regulation is referred to as glucose homeostasis. Insulin, which lowers blood sugar, and glucagon, which raises it, are the most well known of the hormones involved, but more recent discoveries of other glucoregulatory hormones have expanded the understanding of this process.[1] Mechanisms[edit] Blood sugar regulation the flatline is the level needed the sine wave the fluctuations. Blood sugar levels are regulated by negative feedback in order to keep the body in balance. The levels of glucose in the blood are monitored by many tissues, but the cells in the pancreatic islets are among the most well understood and important. Glucagon[edit] If the blood glucose level falls to dangerous levels (as during very heavy exercise or lack of food for extended periods), the alpha cells of the pancreas release glucagon, a hormone whose effects on liver cells act to increase blood glucose levels. They convert glycogen into glucose (this process is called glycogenolysis). The glucose is released into the bloodstream, increasing blood sugar. Hypoglycemia, the state of having low blood sugar, is treated by restoring the blood glucose level to normal by the ingestion or administration of dextrose or carbohydrate foods. It is often self-diagnosed and self-medicated orally by the ingestion of balanced meals. In more severe circumstances, it is treated by injection or infusion of glucagon. Insulin[edit] When levels of blood sugar rise, whether as a result of glycogen conversion, or from digestion of a meal, a different hormone is released from beta cells found in the Islets of Langerhans in the p Continue reading >>

Sleeping, Waking, … And Glucose Homeostasis

Sleeping, Waking, … And Glucose Homeostasis

Citation: (2004) Sleeping, Waking, … and Glucose Homeostasis. PLoS Biol 2(11): e415. Published: November 2, 2004 Copyright: © 2004 Public Library of Science. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. We often think of ourselves as either a day person or a night person—one who rises with the sun, raring to go, or one who prefers to stay up through the night to get things done. Regardless, we each have our regular waking and sleeping cycles. It's been known for some time that variations in sleep and wakefulness are part of our circadian rhythm, or molecular clock. A portion of the brain called the hypothalamic suprachiasmatic nucleus (SCN) regulates this biorhythm. When this area of the hypothalamus is destroyed in animal models, the circadian rhythm is disrupted. Two transcription factors (proteins that regulate gene expression) called Bmal1 and Clock regulate aspects of circadian rhythm, possibly by regulating neurons in the SCN. Other aspects of human physiology are also regulated in a circadian manner. Besides altering sleep and wakefulness patterns, ablation of the SCN alters the ability to regulate sugar levels. Sugar (glucose) levels must be maintained within fairly narrow limits for survival. This regulation is controlled in part by a balance between blood sugar level and insulin production (insulin lowers the blood sugar level). In people and in mouse models, both glucose level and insulin level are subject to circadian rhythms. It isn't clear, however, if this is a behavioral effect, whereby the disruption of the SCN might alter our feeling of being well fed—that is, being Continue reading >>

The Liver And Blood Glucose Levels

The Liver And Blood Glucose Levels

Tweet Glucose is the key source of energy for the human body. Supply of this vital nutrient is carried through the bloodstream to many of the body’s cells. The liver produces, stores and releases glucose depending on the body’s need for glucose, a monosaccharide. This is primarily indicated by the hormones insulin - the main regulator of sugar in the blood - and glucagon. In fact, the liver acts as the body’s glucose reservoir and helps to keep your circulating blood sugar levels and other body fuels steady and constant. How the liver regulates blood glucose During absorption and digestion, the carbohydrates in the food you eat are reduced to their simplest form, glucose. Excess glucose is then removed from the blood, with the majority of it being converted into glycogen, the storage form of glucose, by the liver’s hepatic cells via a process called glycogenesis. Glycogenolysis When blood glucose concentration declines, the liver initiates glycogenolysis. The hepatic cells reconvert their glycogen stores into glucose, and continually release them into the blood until levels approach normal range. However, when blood glucose levels fall during a long fast, the body’s glycogen stores dwindle and additional sources of blood sugar are required. To help make up this shortfall, the liver, along with the kidneys, uses amino acids, lactic acid and glycerol to produce glucose. This process is known as gluconeogenesis. The liver may also convert other sugars such as sucrose, fructose, and galactose into glucose if your body’s glucose needs not being met by your diet. Ketones Ketones are alternative fuels that are produced by the liver from fats when sugar is in short supply. When your body’s glycogen storage runs low, the body starts conserving the sugar supplies fo Continue reading >>

What Is Insulin?

What Is Insulin?

Insulin is a hormone; a chemical messenger produced in one part of the body to have an action on another. It is a protein responsible for regulating blood glucose levels as part of metabolism.1 The body manufactures insulin in the pancreas, and the hormone is secreted by its beta cells, primarily in response to glucose.1 The beta cells of the pancreas are perfectly designed "fuel sensors" stimulated by glucose.2 As glucose levels rise in the plasma of the blood, uptake and metabolism by the pancreas beta cells are enhanced, leading to insulin secretion.1 Insulin has two modes of action on the body - an excitatory one and an inhibitory one:3 Insulin stimulates glucose uptake and lipid synthesis It inhibits the breakdown of lipids, proteins and glycogen, and inhibits the glucose pathway (gluconeogenesis) and production of ketone bodies (ketogenesis). What is the pancreas? The pancreas is the organ responsible for controlling sugar levels. It is part of the digestive system and located in the abdomen, behind the stomach and next to the duodenum - the first part of the small intestine.4 The pancreas has two main functional components:4,5 Exocrine cells - cells that release digestive enzymes into the gut via the pancreatic duct The endocrine pancreas - islands of cells known as the islets of Langerhans within the "sea" of exocrine tissue; islets release hormones such as insulin and glucagon into the blood to control blood sugar levels. Islets are highly vascularized (supplied by blood vessels) and specialized to monitor nutrients in the blood.2 The alpha cells of the islets secrete glucagon while the beta cells - the most abundant of the islet cells - release insulin.5 The release of insulin in response to elevated glucose has two phases - a first around 5-10 minutes after g Continue reading >>

How The Body Controls Blood Sugar - Topic Overview

How The Body Controls Blood Sugar - Topic Overview

The bloodstream carries glucose-a type of sugar produced from the digestion of carbohydrates and other foods-to provide energy to cells throughout the body. Unused glucose is stored mainly in the liver as glycogen. Insulin, glucagon, and other hormone levels rise and fall to keep blood sugar in a normal range. Too little or too much of these hormones can cause blood sugar levels to fall too low (hypoglycemia) or rise too high (hyperglycemia). Normally, blood glucose levels increase after you eat a meal. When blood sugar rises, cells in the pancreas release insulin, causing the body to absorb glucose from the blood and lowering the blood sugar level to normal. When blood sugar drops too low, the level of insulin declines and other cells in the pancreas release glucagon, which causes the liver to turn stored glycogen back into glucose and release it into the blood. This brings blood sugar levels back up to normal. Continue reading >>

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