52 terms

ER4 - The Endocrine pancreas

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What refers to all chemical reactions occurring within cells of the body?
Metabolism
What refers to reactions involving catabolism (breakdown), anabolism (build up) and transformation of protein, carbohydrate and fat?
Fuel Metabolism
What hormone regulates metabolic rate?
Thyroid hormone
What are the clusters of endocrine cells found in the pancreas?
Islets of Langerhans
What secretory cells do the islets of Langerhans have? (4)
- alpha cells
- beta cells
- delta cells
- f cells
What do alpha-cells release from the Islets of Langerhans? This hormone favours catabolism (hormone of hungry state)
Glucagon
What do beta-cells release from the Islets of Langerhans? This hormone favours anabolism (hormone of fed state)
Insulin
What do delta-cells release from the Islets of Langerhans? This hormone decreases absorption from the gut to prevent excessive plasma levels of nutrients
Somatostatin
What do F cells release from the islets of langerhans?
Pancreatic polypeptide
Cell diagram
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How long is the half life of Insulin?
30 mins
How long is the half life of Glucagon?
10 mins
What does a mature insulin molecule consist of?
2 peptide chains joined by disulfide linkages
How many amino acids does a mature insulin molecule have?
51 (21 on the A chain and 30 on the B chain)
What is the role of insulin?
Insulin integrates body fuel metabolism both during periods of fasting and during feeding
Describe insulin secretion during fasting
The beta cell secretes less insulin
What does the secretion of less insulin do to lipids?
Lipids are mobilized from adipose tissue
What does secretion of less insulin do to amino acids?
Amino acids are mobilized from muscle and other tissues
Describe insulin secretion during feeding
The beta cells secrete more insulin
What does secretion of more insulin due to feeding cause? (2)
- catabolism of endogenous fuel stores is inhibited
- CHO, lipid and AA uptake by specific insulin sensitive tissues is stimulated
What is the primary fuel for cells within the CNS?
Glucose
What is the name of the condition for when there is less than 4 mM of glucose in the bloodstream? It results in confusion, seizures and coma
Hypoglycemia
What is the name for the condition for when there is more than 7mM of glucose in the bloodstream when fasting and more than 11 mM 2h after meals? It is a characteristic of the diabetic state. Can result in severe dehydration, hypotension and vascular collapse
Hypergylcemia
In healthy individuals what is the range for plasma [glucose]?
After an overnight fast: 4-5mM
Does not exceed 10mM after a meal
What does insulin cause to be inserted into the plasma membrane?
Glucose Transporter Proteins (GLUT4)
What is caused by the inadequate insulin action leading to an abnormally high blood glucose concentration?
Diabetes Mellitus
How can you test for Diabetes Mellitus?
Oral Glucose Tolerance Test
What cells release glucagon from the Islets of Langerhans?
Alpha Cells
What cells release insulin from the Islets of Langerhans?
Beta Cells
What cells release somatostatin from the Islets of Langerhans?
Delta Cells
An increase in what factors promotes the secretion of Insulin?
Glucose Concentration,
Amino Acid Concentration,
Parasympathetic Activity,
Glucagon
An increase in what factors inhibits secretion of Insulin?
Sympathetic Activity,
Somatostatin Concentration,
Cortisol Concentration
What factors increase secretion of Glucagon?
Decrease in Blood Glucose Concentration,
Increase in Amino Acid Concentration,
Decrease in Free Fatty Acid Concentration,
Increase in Sympathetic Activity (exercise)
What does sympathetic stimulation of the autonomic nervous system in the Islet do?
Inhibits insulin secretion
What does parasympathetic stimulation of the autonomic system in the Islet do?
Stimulates insulin secretion
What does exercise do to insulin secretion?
Suppresses it
What is the primary stimulus for insulin secretion?
Glucagon
What 3 peptides enhance insulin secretion?
- CCK
- GLP-1
- GIP
What are the three principle target tissues for insulin?
- liver
- skeletal muscle
- adipose tissue
Give three insulin insensitive cells
Brain, kidneys and RBCs
What does insulin do in the liver? (5)
- Promotes the synthesis of glycogen
- Inhibits glycogenolysis
- Inhibits glucogenesis
- Promotes the storage of fats as triglycerides and inhibits the oxidation of fatty acids
- Stimulates the synthesis of protein and simultaneously reduces the degradation of protein within the liver
What does insulin do in skeletal muscle cells?
- Stimulates glucose uptake
- Enhances conversion of glucose to glycogen
- Increases glucose breakdown and oxidation
- Stimulates protein synthesis and slows protein degradation
What does insulin do in adipose tissue?
- increases glucose uptake as a result of increased GLUT4 PM expression
- promotes the breakdown of glucose to metabolites that will eventually be used to synthesise triglycerides
- promotes formation of triglycerides and inhibits hormone sensitive triglyceride lipase
- induces synthesis of lipoprotein lipase which is exported from the cell to the e/c surface of endothelial cells
What type of diabetes has the following features?:
- little/ no insulin secretion
- defect in B- cell function
- insulin injections for treatment
- symptoms develop rapidly
Type 1 diabetes (IDDM)
What type of diabetes has the following features?:
- insulin secretion may be normal
- defect in insulin sensitivity
- diet/ exercise and oral drugs for treatment
- symptoms develop slowly
Type 2 diabetes (NIDDM)
What does the inability of cells to utilize glucose in DM cause?
A compensatory increase in lipolysis to generate fatty acids as an energy source
What do pancreatic alpha cells secrete in response to ingested protein?
Glucagon
What inhibits glucagon secretion?
Glucose
What does glucagon stimulate in the liver?
Glycogenolysis, gluconeogenesis and ketogenesis
What does glucagon stimulate in cardiac and skeletal muscle?
Glycogenesis
What is somatostatin secreted by?
- delta cells of the pancreatic islets of Langerhans
- D cells of the GI tract
- hypothalamus
- several other sites in the CNS
What does somatostatin inhibit?
The secretion of growth hormone, insulin, glucagon, gastrin and TSH