Control of Blood Glucose Concentration

• What two hormones control blood glucose concentration?

  Insulin and glucagon
• Why are hormonal responses slower than nervous impulses?

  They travel in the blood to target cells
• How do hormonal responses differ from nervous impulses in terms of area affected?

  Hormonal responses can occur all over the body
• Why do hormonal effects tend to last longer than neurotransmitter effects?

  Hormones are not broken down as quickly
• What are the Islets of Langerhans?

  Clusters of cells in the pancreas
• What do β cells in the Islets of Langerhans secrete?

  Insulin
• What do α cells in the Islets of Langerhans secrete?

  Glucagon
• How do insulin and glucagon function in the body?

  They act on effectors to restore blood glucose
• What is the role of insulin and glucagon in blood glucose regulation?

  • Insulin lowers blood glucose levels
  • Glucagon raises blood glucose levels
  • Both hormones work to maintain homeostasis
• What effect does insulin have on blood glucose concentration?

  It lowers blood glucose concentration
• How does insulin lower blood glucose concentration?

  By binding to specific receptors on cell membranes
• What type of cells does insulin bind to in the body?

  Muscle cells and hepatocytes
• What happens to cell membranes when insulin binds to them?

  They become more permeable to glucose
• What is glycogenesis?

  The process of forming glycogen from glucose
• How does insulin affect glycogen formation in muscle cells?

  It activates enzymes that convert glucose into glycogen
• Where do cells store glycogen?

  In their cytoplasm
• What effect does insulin have on the rate of respiration of glucose?

  It increases the rate of respiration of glucose
• What effect does glucagon have on blood glucose concentration?

  It raises blood glucose concentration
• How does glucagon raise blood glucose concentration?

  By binding to receptors on hepatocytes
• What is glycogenolysis?

  The process of breaking down glycogen
• What is gluconeogenesis?

  The process of forming glucose from non-carbohydrates
• What does glucagon activate in the body?

  Enzymes that form glucose from glycerol and amino acids
• How does glucagon affect the rate of respiration of glucose?

  It decreases the rate of respiration of glucose
• What happens when the pancreas detects high blood glucose concentration?

  The β cells secrete insulin
• What do the α cells do when blood glucose is high?

  They stop secreting glucagon
• What is the response of hepatocytes and muscle cells to insulin?

  They decrease blood glucose concentration
• What happens to blood glucose concentration after insulin acts?

  It returns to normal
• What do α cells secrete when blood glucose is too low?

  Glucagon
• What happens to β cells when blood glucose is low?

  They stop secreting insulin
• What do glucagon receptors bind to?

  Hepatocytes
• How do hepatocytes respond to glucagon?

  They increase blood glucose concentration
• What happens to blood glucose concentration after glucagon action?

  It returns to normal
• What are glucose transporters?

  Channel proteins for glucose transport
• Which glucose transporter is found in skeletal and cardiac muscle cells?

  GLUT4
• What happens to GLUT4 when insulin levels are low?

  It is stored in vesicles
• What triggers GLUT4 to move to the cell membrane?

  Insulin binding to receptors
• How does glucose enter the cell through GLUT4?

  By facilitated diffusion
• What hormone is secreted when blood glucose is low?

  Adrenaline
• What effect does adrenaline have on blood glucose concentration?

  It increases blood glucose concentration
• What processes does adrenaline activate in hepatocytes?

  Glycogenolysis