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3.6.4.2 Control of blood glucose concentration - Coggle Diagram
3.6.4.2 Control of blood glucose concentration
Hormonal Transmission
Protein Hormones
Large and potentiially hydrophilic, transported in aquesous blood
Bind to complementary receptors on target cells and initiate a s response by the cell
Steroid (lipid) hormones
Small and hydrophobic - based on cholesterol structure, Act upon DNA in the nucleus
Diffuse across the phosophlipid bilayer of cells
Natural sources of blood glucose
Directly from the diet
Break down of glycogen (glycogenolysis)
gluconeogenesis - prodcution of new glucose from sources other than carbohydrates
Pancreas
Exocrine function - secretes digestive enzymes into the pancreatic duct
Endocrine function - secretes hormones directly into the blood
Islets Of Langerhans
Alpha Cells - produce and secrete glycagon
Beta Cells - produce and secrete insulin
Insulin and Beta Cells
If blood glucose becomes high, Beta cells act as a controller and detect this stimulus
Beta cells secrete insulin (a peptide hormone) into the blood
Insulin binds with a complementary cell surface receptor protein found on the surface of most body cells
Binding activates protein kinase enzymes to increase the rate of respiration (increase glucose consumption), increase glycogenesis (using many glucoses to form glycogen in liver and muscle cells), increase rate of lipogenesis (using glucose to synthesis lipid in liver cells), increase permeability of cells to glucose (more glucose transporter channels are inserted into the membrane)
Stimulus
High Blood Glucose Concentration
Receptor
Beta Cells in Pancreas
Hormone Released
Insulin
Traget Cells
Insulin binds to receptors on membrane of liver and muscle cells
Action of effector cells
Glucose transporters inserted into cell membrane. Glycogenesis, lipogenesis, increased respiration. Glucose removed from blood
Negative Feedback Lopp
Beta cells detect set point reach. stop releasing insulin
Glucagon and Alpha Cells
If blood glucose becomes lower than normal, alpha cells in the pancreas act as receptors and detect this stimulus
Alpha cells secrete glucagon (peptide hormone) into the blood
Glucagon binds to complementary cell surface receptor proteins found on the surface of liver cells only.
secondary messenger model
Glucagon binds to a specific cell surface receptor protein on liver cell membranes.
This causes the membrane to change shape, activating a membrane bound enzyme called adenyl cyclase.
This enzyme converts ATP to cyclic AMP. cAMP activates the protein kinase enzymes. These enzymes cause increased glycogenolysis and gluconeogenesis.
This results in increased glucose concentration in cells and a faster rate of diffusion of glucose into the blood.
Adrenaline
Adrenaline in another hormone that increases blood sugar levels in response to pain/shock 'fight or flight' response
Its produced in the adrenal glands and binds to complementary receptors on liver cell membranes and activates the same secondary messenger model as glucagon
It raises blood glucose by activating the enzyme that causes the breakdown of glycogen to glucose in the liver and inactivating an enzyme that synthesises glycogen
Diabetes
The partial or complete breakdown of glucose homeostasis
affects ~1.6 million people in the UK
Type 1
Caused by autoimmune condition, their immune system has destroyed the beta cells. Needs alleles, genetic risk and environmental factors, infected with virus
Insulin dependent diabetes mellitus. The beta cells don't produce insulin in response to high concentration of glucose in the blood
Onset in children, very quickly over a few weeks
Extreme symptoms: high blood glucose, glucose in urine, thirst, excessive urination
After eating a meal they measure their blood glucose, and inject a specific volume of insulin to reduce their blood glusoce. insulin pump
Type 2
Caused by cells no longer responding to insulin due to genetic factors, insulin receptors are less complementary. Environmental factors, persistent high blood glucose levels due to a diet with lots of sugars, simple carbs, obesity
Insulin resistant diabtes mellitus. Other cells of the body no longer respond to insulin
Onset in older adults (40+), very slowly over months/years
Gradual symptoms
Control with exercise, control carb intake, lose weight, lower glucose levels with specific drugs