6.4.2 Control of Blood Glucose Concentration Flashcards
Define endocrine system
Series of glands throughout body which produce and secrete hormones
Define hormone
Chemical messengers transported around body in blood plasma to act on target cells
What feature of target cells allows hormones to act on them?
Glycoprotein receptors on membrane complementary to specific hormone
How does the endocrine system compare to the nervous system?
Slower but longer-lasting effects
Give nine examples of glands that are part of the endocrine system
Pituitary gland Thyroid Thymus Adrenal Pancreas Kidneys Uterus Ovaries Testes
Give three factors that influence blood glucose levels
Diet
Breakdown of glycogen
Production of glucose from non-carbohydrate sources
What is the normal blood glucose concentration?
5 mmol/dm3
Why is blood glucose concentration regulation important?
Too high, water potential of blood falls
Too low, cells can’t respire and die
Define glycogenesis
Glucose removed from blood and stored in cytoplasm of hepatocytes (liver cells) as glycogen by the liver
Define glycogenolysis
Liver converts glycogen back into glucose and glucose diffuses into blood
Define gluconeogenesis
Formation of glucose from non-carbohydrates by liver when glycogen supply is exhausted
Describe the exocrine function of the pancreas
Secretes digestive enzymes into pancreatic duct by:
Pancreatic cells surround small tubules which drain into pancreatic duct
Pancreatic cells produce pancreatic juice made up of amylase, trypsinogen and lipase
Describe the endocrine function of the pancreas
Secretes hormones from alpha/beta cells in islets of Langerhans directly into blood
What kind of feedback controls blood glucose concentration?
Negative
What happens when blood glucose is too high?
Insulin secreted by beta cells in islets of Langerhans
Insulin binds to specific receptors on surface membrane of cells
How does the action of insulin binding to the receptors increase the intake of glucose from the blood into cells? How does this decrease blood glucose concentration?
Tertiary structure of glucose transport carrier proteins changes so they open
Number of glucose transport carrier proteins e.g. GLUT4 increase
Respiratory rate of cells increases so more glucose is used up so more glucose diffuses into cells
How else does the action of insulin binding to the receptors decrease blood glucose concentration?
Activates enzymes for glycogenesis in liver/muscle cells and conversion of glucose into fat so the rate of these reactions increases
Describe the action of glucagon to increase blood glucose concentration
Secreted by alpha cells in islets of Langerhan
Attach to specific protein receptors on cell-surface membrane of liver cells
Activates enzymes that perform glycogenolysis
Activating enzymes involved in the conversion of amino acids and glycerol into glucose (gluconeogenesis)
Decrease in rate of respiration
Describe the action of adrenaline to increase blood glucose concentration
Attach to specific receptors on hepatocytes
Activates enzymes involved in glycogenolysis
Glucose secretion
Glycogensis inhibition
Inhibition of insulin secretion
What does the second messenger model describe?
How glycogen and adrenaline are able to activate glycogenolysis inside a cell without entering it
Besides glucagon and adrenaline, what four named molecules are involved in the second messenger model?
Adenylate cyclase
ATP
Cyclic AMP
Protein kinase
Describe the process shown in the second messenger model (6 steps)
- Glucagon or adrenaline bind to specific membrane receptor (first messenger)
- Binding causes receptor to change shape on inside of membrane, activates adenylate cyclase
- Activated adenylate cyclase converts ATP into cyclic AMP (cAMP)
- cAMP (second messenger) activates protein kinase, causing protein kinase to change shape
- Activated protein kinase catalyses glycogen into glucose
- Glucose moves out of liver by facilitated diffusion through channel proteins into the blood
Define diabetes
Metabolic disorder where blood glucose concentration can’t be controlled properly
Give five symptoms of diabetes
Thirsty Tired Blurred vision Weight loss Cuts not healing
What is the cause of type 1 diabetes?
Immune system attacks beta cells in islets of Langerhans so can’t produce insulin
What are the causes of type 2 diabetes?
Glycoprotein receptors on cells don’t respond to insulin/beta cells don’t produce enough insulin
How does the age of onset compare for type 1 and type 2 diabetes?
Type 1 develops quickly and tends to develop in childhood
Type 2 develops slowly, usually in adults over 40 but cases in young people increasing
Give two treatments for type 1 diabetes
Monitor blood glucose concentration
Injecting insulin
Give four treatments for type 2 diabetes
Healthy balanced diet
Regular exercise
Drugs to stimulate insulin production/reduced rate of absorption in small intestine,
Insulin injections
