L30. Physiology - Endocrine Pancreas

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Questions and Answers

Which of the following processes is not directly antagonized by insulin?

  • Glycogenesis (correct)
  • Glycogenolysis
  • Lipolysis
  • Gluconeogenesis

What is the primary effect of insulin on hepatic gluconeogenesis?

  • Suppresses gluconeogenesis to decrease blood glucose levels (correct)
  • Increases gluconeogenesis to provide energy for muscle cells
  • Stimulates gluconeogenesis to increase blood glucose levels
  • Has no effect on gluconeogenesis

Which two electrolytes does insulin increase the cellular uptake of?

  • Sodium and Calcium
  • Potassium and Sodium
  • Calcium and Phosphate
  • Potassium and Phosphate (correct)

Which of these statements about the insulin receptor is true?

<p>It is a tyrosine kinase receptor, triggering phosphorylation of IRS proteins (C)</p> Signup and view all the answers

Which of the following molecules is not a target of insulin's direct action?

<p>Insulin receptor substrate (IRS) proteins (B)</p> Signup and view all the answers

Which of these pairs is correctly matched with its effect from insulin's action?

<p>Lipolysis: Decreased (B)</p> Signup and view all the answers

What is the significance of the phosphorylation of IRS proteins in insulin signaling?

<p>It serves as a docking site for other signaling proteins, initiating downstream effects (B)</p> Signup and view all the answers

Which of these statements best describes the role of insulin in regulating glucose metabolism?

<p>It acts as a primary antagonist to glucagon, promoting glucose storage and utilization (D)</p> Signup and view all the answers

What is the direct consequence of excess amino acids being diverted to glucose via gluconeogenesis in the liver?

<p>Increased plasma glucose levels (B)</p> Signup and view all the answers

How does glucagon contribute to the prevention of hypoglycemia after a pure protein meal?

<p>Glucagon promotes the conversion of amino acids into glucose in the liver. (B)</p> Signup and view all the answers

What is the primary role of insulin in regulating blood glucose levels after a pure protein meal?

<p>Insulin promotes the storage of glucose in muscle and fat tissue. (A)</p> Signup and view all the answers

What is the primary reason why a pure protein diet can lead to hypoglycemia?

<p>Proteins are low in carbohydrates, the primary energy source for the body. (D)</p> Signup and view all the answers

Which of the following statements accurately describes the interaction between glucagon and insulin in response to a pure protein meal?

<p>Insulin stimulates glucose uptake while glucagon promotes gluconeogenesis to prevent hypoglycemia. (A)</p> Signup and view all the answers

What is the mechanism by which amino acids prevent hypoglycemia after a pure protein meal?

<p>Amino acids stimulate the secretion of glucagon, promoting gluconeogenesis. (A)</p> Signup and view all the answers

How does the stimulation of insulin secretion by amino acids contribute to the regulation of blood glucose levels after a pure protein meal?

<p>Insulin promotes the absorption and storage of glucose from the blood. (C)</p> Signup and view all the answers

Why is the concurrent stimulation of both glucagon and insulin secretion essential after a pure protein meal?

<p>It prevents both hyperglycemia and hypoglycemia by balancing glucose production and storage. (B)</p> Signup and view all the answers

What is the primary physiological consequence of increased glucagon secretion following a pure protein meal?

<p>Promoting the conversion of amino acids into glucose via gluconeogenesis. (A)</p> Signup and view all the answers

Which of the following statements correctly describes the interaction between glucagon and insulin following a protein-rich meal?

<p>Insulin is initially dominant, but glucagon takes over to promote glucose production. (C)</p> Signup and view all the answers

What is the primary function of insulin secretion stimulated by amino acids following a protein-rich meal?

<p>To enhance the absorption of glucose by muscle and fat tissues (C)</p> Signup and view all the answers

What is a key physiological consequence of the autoimmune destruction of beta islet cells in Type 1 Diabetes?

<p>Inability to produce sufficient insulin, leading to hyperglycemia (B)</p> Signup and view all the answers

Which of the following treatment options for Type 1 Diabetes is specifically aimed at restoring insulin production?

<p>Tissue regeneration from stem cells (B)</p> Signup and view all the answers

The mechanism of action for which of the following treatments for Type 1 Diabetes is most focused on protecting existing beta islet cells from further damage?

<p>Immuno-modulation treatments (A)</p> Signup and view all the answers

What is the underlying pathological basis for Type 2 Diabetes?

<p>Impaired insulin sensitivity, resulting in resistance to insulin action. (C)</p> Signup and view all the answers

Why is Type 2 Diabetes considered more complex and difficult to treat compared to Type 1 Diabetes?

<p>It involves multiple genetic and environmental factors, leading to varied clinical manifestations. (B)</p> Signup and view all the answers

Which of these pathways are involved in the modulation of insulin secretion by neural and hormonal modulators?

<p>PLC pathway (A), cAMP/PKA pathway (D)</p> Signup and view all the answers

What is the immediate precursor of insulin?

<p>Proinsulin (D)</p> Signup and view all the answers

What is the role of C-peptide in the synthesis of insulin?

<p>C-peptide is a by-product of insulin synthesis. (C)</p> Signup and view all the answers

Which of the following processes is stimulated by insulin in the context of anabolism?

<p>Synthesis of glycogen (glycogenesis) (D)</p> Signup and view all the answers

What is the main effect of insulin on catabolic processes?

<p>Insulin inhibits catabolic processes. (A)</p> Signup and view all the answers

How does insulin act to increase cellular uptake of glucose?

<p>By increasing the production of glucose transporters on the cell membrane. (A)</p> Signup and view all the answers

What type of receptor does insulin bind to?

<p>Tyrosine kinase receptor (B)</p> Signup and view all the answers

What is the role of calcium ions (Ca++) in the release of insulin?

<p>Calcium ions are involved in the exocytosis of insulin secretory granules. (D)</p> Signup and view all the answers

Which of the following factors directly influences glucagon secretion?

<p>Serum levels of amino acids (B)</p> Signup and view all the answers

What effect do glucose and fatty acids have on glucagon secretion?

<p>They inhibit glucagon secretion. (B)</p> Signup and view all the answers

What is the relationship between glucagon secretion and the metabolism of carbohydrates, proteins, and fats?

<p>Glucagon secretion is directly linked to the metabolism of carbohydrates, proteins, and fats. (B)</p> Signup and view all the answers

Which of the following signaling pathways can stimulate glucagon secretion?

<p>α-adrenergic signaling (D)</p> Signup and view all the answers

Which of the following hormones is directly involved in the regulation of glucagon secretion?

<p>Insulin (D)</p> Signup and view all the answers

What is the primary function of glucagon?

<p>To promote glycogen breakdown and glucose release (C)</p> Signup and view all the answers

Which of the following statements is TRUE regarding the regulation of glucagon secretion?

<p>Low levels of glucose stimulate glucagon secretion. (A)</p> Signup and view all the answers

What is the physiological significance of glucagon's regulation by amino acids?

<p>To increase the use of amino acids for energy production during fasting (C)</p> Signup and view all the answers

What is the primary outcome of glucagon's effect on amino acids?

<p>Increased production of nitrogenous waste (C)</p> Signup and view all the answers

What metabolic condition is directly linked to excessive glucagon secretion, as described in the text?

<p>Insulin insufficiency (D)</p> Signup and view all the answers

Which of the following is not a hallmark of diabetes mellitus as mentioned in the text?

<p>Increased insulin sensitivity (D)</p> Signup and view all the answers

What is the primary role of glucagon in the body?

<p>To increase blood glucose levels when they are low (C)</p> Signup and view all the answers

Which type of meal is most likely to stimulate the simultaneous release of both glucagon and insulin?

<p>High-carbohydrate meal (B)</p> Signup and view all the answers

What process does glucagon stimulate to increase blood glucose levels?

<p>Glycogenolysis (B)</p> Signup and view all the answers

The text mentions that excessive glucagon secretion compounds the problems of insulin insufficiency, what does this suggest about glucagon's role in diabetes mellitus?

<p>Glucagon exacerbates the effects of insulin deficiency. (A)</p> Signup and view all the answers

What is the main reason for increased ketone body production in diabetes mellitus?

<p>Reduced glucose uptake by cells (D)</p> Signup and view all the answers

Flashcards

Intracellular Ca++ and Insulin

Increase in intracellular Ca++ causes exocytosis of insulin secretory granules.

cAMP/PKA Pathway

A pathway that modulates insulin secretion and promotes vesicle fusion.

PLC Pathway

Another pathway involved in the regulation of insulin secretion, can either promote or inhibit vesicle fusion.

Preproinsulin

Initial form of insulin before conversion to proinsulin.

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Proinsulin

Form of insulin that is produced after preproinsulin and before active insulin.

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Insulin Action: Anabolism

Insulin stimulates anabolism by increasing uptake of glucose, fatty acids, and amino acids.

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Insulin Action: Catabolism

Insulin antagonizes catabolism by decreasing glycogenolysis, lipolysis, and proteolysis.

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Electrolyte Balance and Insulin

Insulin alters electrolyte balance in the body.

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Insulin's role in catabolism

Insulin decreases glycogenolysis, lipolysis, and proteolysis.

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Gluconeogenesis

The process of forming glucose from non-carbohydrate sources, suppressed by insulin.

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Electrolyte balance

Insulin increases cellular uptake of potassium and phosphate, decreases sodium and calcium uptake.

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Insulin receptor type

Insulin binds at a tyrosine kinase receptor on the cell surface.

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Insulin signaling pathway

Downstream effects vary by tissue but involve the phosphorylation of an IRS protein.

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Glycogenolysis

Breakdown of glycogen into glucose, reduced by insulin action.

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Lipolysis

The breakdown of fats into fatty acids, antagonized by insulin.

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Potassium uptake

Insulin promotes the cellular uptake of potassium, aiding electrolyte balance.

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Amino Acids and Insulin

Amino acids stimulate insulin secretion, promoting glucose storage.

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Glucagon's Role

Glucagon helps convert excess amino acids into glucose via gluconeogenesis.

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Hypoglycemia Prevention

Insulin and glucagon secretion prevents low blood sugar from protein-only diets.

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Hyperglycemia Prevention

Simultaneous insulin and glucagon prevent high blood sugar after protein meals.

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Concurrent Hormone Secretion

Amino acids stimulate both insulin and glucagon secretion at the same time.

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Insulin and Fat Tissue

Insulin promotes glucose absorption and storage in fat and muscle tissues.

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Amino Acids in Metabolism

Amino acids are pivotal in regulating blood glucose through hormonal stimulation.

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GLP

Glucagon-like proteins that play a role in metabolism regulation.

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Glucagon Regulation

The process by which glucagon levels are controlled by glucose, amino acids, and fatty acids.

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Inhibition of Glucagon

Glucose and fatty acids inhibit the secretion of glucagon.

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Stimulation of Glucagon

Amino acids stimulate the secretion of glucagon when levels are high.

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Metabolism Link

Glucagon secretion is linked to the metabolism of carbohydrates, proteins, and fats.

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Sensory Stimulation

Glucagon secretion can be influenced by sensory inputs like pain or loud noise.

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α-adrenergic Signaling

Activation of α-adrenergic signaling stimulates glucagon secretion.

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SANS and PANS

Sympathetic and parasympathetic autonomic nervous systems both influence glucagon secretion.

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Glucagon

A hormone that promotes gluconeogenesis and lipolysis, especially in diabetes.

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Hyperglycemia

An abnormally high level of glucose in the blood, characteristic of diabetes.

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Negative Nitrogen Balance

A state where nitrogen excretion exceeds nitrogen intake, often due to increased gluconeogenesis.

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Ketone Bodies

Byproducts of fat metabolism that increase during insulin insufficiency in diabetes.

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Diabetes Mellitus

A metabolic disorder characterized by high blood glucose levels and insulin insufficiency.

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Insulin

A hormone that lowers blood glucose levels by facilitating its uptake into cells.

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Glucagon and Insulin Secretion

Amino acids stimulate both glucagon and insulin secretion after a protein meal.

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Prevention of Hypoglycemia

Glucagon helps prevent hypoglycemia that might occur from a protein-only diet.

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Role of Insulin After Meal

Insulin promotes absorption and storage of glucose by tissues after food intake.

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Type 1 Diabetes Cause

Type 1 diabetes results from autoimmune destruction of beta islet cells in the pancreas.

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Type 1 Diabetes Treatments

Possible treatments include hormone replacement, organ transplant, and stem cell regeneration.

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Complexity of Type 2 Diabetes

Type 2 diabetes has a more complex progression and treatment challenges than Type 1.

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Amino Acids and Hormone Secretion

Amino acids trigger concurrent secretion of insulin and glucagon after protein intake.

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Study Notes

Glucose Homeostasis

  • Blood glucose levels are maintained at 100 mg/dL
  • Insulin is secreted in response to high blood glucose, stimulating glucose absorption and storage
  • Glucagon is secreted in response to low blood glucose, stimulating glucose synthesis by the liver

Pancreatic Hormones

  • Glucagon is produced by alpha cells
  • Insulin is produced by beta cells
  • Somatostatin is produced by delta (D) cells

Regulation of Insulin Release

  • Cephalic phase: PANS-mediated
  • Early postprandial phase: incretin-mediated
  • Postprandial phase: blood glucose-mediated

Pancreatic Hormones

  • Incretins (GLP1 and GIP) are peptide hormones produced by L-cells in the gut lining
  • They are secreted into the bloodstream after food
  • They act on the pancreas to enhance insulin secretion

Regulation of Insulin Release

  • Insulin release is proportional to blood glucose levels
  • Insulin secretion is linked to glucose metabolism exocytosis

Regulation of Insulin Release - Steps in Beta Islet Cells

  • Glucose enters the cell via GLUT2
  • Glucose metabolism produces ATP
  • ATP inhibits K+ channels, producing depolarization of the cell
  • Depolarization causes Ca++ influx
  • Increased intracellular Ca++ causes exocytosis of insulin secretory granules

Insulin Synthesis

  • Insulin is initially produced as preproinsulin
  • Then converted to proinsulin
  • Proteolysis of proinsulin produces insulin and C peptide

Insulin Action

  • Stimulates anabolism: increases cellular uptake of glucose, fatty acids, and amino acids; stimulates their conversion to glycogen, triglycerides, and protein
  • Antagonizes catabolism: decreases glycogenolysis, lipolysis, and proteolysis; suppresses hepatic gluconeogenesis
  • Alters electrolyte balance: increases cellular uptake of potassium and phosphate; decreases cellular uptake of sodium and calcium

Insulin Signaling

  • Insulin binds to a tyrosine kinase receptor on the cell surface
  • This activates IRS (insulin receptor substrate), which serves as a docking site for intracellular signaling proteins

Insulin Effects - Liver

  • Suppresses glucose output
  • Stimulates glycogen synthesis
  • Promotes fat synthesis and storage
  • Stimulates VLDL release
  • Promotes protein synthesis
  • Inhibits protein breakdown

Insulin Effects - Muscle and Adipose Tissue

  • Mediates glucose uptake by recruiting GLUT4 transporters
  • Promotes glycogen synthesis
  • Promotes fatty acid storage in triglycerides

Glucagon Production

  • Glucagon is produced by alpha cells in the outer mantle of islets
  • Preproglucagon, a 29 aa peptide, is initially produced
  • Later cleaved into GLP1 and GLP2 by intestinal L cells

Glucagon Regulation

  • Glucagon secretion is primarily regulated by blood glucose, amino acids, and fatty acids
  • Glucose and fatty acids inhibit glucagon secretion
  • Amino acids stimulate secretion

Glucagon Effects

  • Stimulates gluconeogenesis and glycogenolysis in liver
  • Stimulates lipolysis in adipose tissue
  • Increases glucose and fatty acid levels

Glucagon Regulation - Additional Factors

  • Sensory stimulation (e.g., loud noise, pain) can affect glucagon secretion
  • ANS signaling (SANS and PANS) affects glucagon secretion

Glucagon Effects

  • Excessive glucagon secretion in diabetes exacerbates symptoms such as hyperglycemia, negative nitrogen balance and ketosis
  • Glucose/amino acids/ fatty acids influence glucagon secretion

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