Homeostasis - Control of Blood Glucose Concentration Flashcards
What happens if blood glucose levels are too high?
- High = Lower water potential of blood.
- Causing water to diffuse out of the cells via osmosis into the blood.
- Leads to a higher blood pressure.
What happens when blood glucose levels are too low?
Not sufficient glucose for respiration, declining energy levels
Where are changes in blood glucose concentrations detected?
- Islets of Langerhans, Pancreas
What is Glycogenesis?
Liver cells produce enzymes converting glucose to glycogen which is then stored n the liver cells.
What is glycogenolysis?
When blood glucose concentration is too low, liver cells produce enzymes that break down glycogen in the cells to glucose.
What is gluconeogenesis?
When blood glucose conc is too low, liver cells also form glucose from glycerol and amino acids.
How does insulin return blood glucose levels to normal?
1) Detected by beta cells in islets of Langerhans of pancreas.
2) Insulin secreted, travels in the blood to liver and muscle cells.
3) Binds to muscle cell receptor membranes inserting more glucose channel proteins in the cell membrane causing the rate of glucose uptake by muscle cells to increase as well as the rate of respiration in muscle cells.
4) Glycogenesis - Insulin binds to receptors on the liver cell membrane. Liver cells produce enzymes that convert glucose to glycogen which is then stored in the liver cell’s cytoplasm.
Why is insulin important?
- Maintains optimum blood water potential by reducing the glucose in the blood, bwp would decrease otherwise.
- Water in the cells would diffuse out, causing cells to shrink and die.
What is the importance of Glucagon?
Increases blood glucose concentration allowing more respiration to occur.
How does glucagon work?
1) Detected by alpha cells in islets of Langerhans of the pancreas.
2) Glucagon is secreted and travels via blood to the liver cells.
3) Glycogenolysis - Glucagon binds to receptors on liver cell membranes, liver cells produce enzymes converting glycogen to glucose.
4) Gluconeogenesis - Glucagon binding to liver cell membrane also causes the release of enzymes, forming glucose from glycerol and amino acids.
5) Glucagon also reduces the rate of respiration slowing the rate at which glucose is used up.
When is adrenaline released?
In response to low blood glucose concentrations, during exercise and in times of stress.
What is the adrenaline response?
1) Adrenaline is secreted from the adrenal gland.
2) Binds to protein receptors in the liver cell membrane.
3) Causes the protein to change shape on the inside of the membrane.
4) This change leads to the activation adenyl cyclase which converts ATP to cyclic AMP (cAMP).
5) cAMP acts as a secondary messenger which binds to protein kinase and changes its shape, activating it.
6) This induces two reactions:
- Activation of glycogenolysis and inhibition of glycogenesis. The glucose moves out via facilitated diffusion and enters the blood.
- Also promotes secretion of glucagon from the pancreas and inhibits secretion of insulin.
What are the features of primary messengers?
- Do not enter the cell.
- Exert action on a cell membrane by binding to receptors and triggering a change within a cell.
- Can initiate a reaction or can activate another molecule
(e. g hormones - adrenaline,glucagon)
What are the features of Secondary Messengers?
- Initiate/coordinate responses that take place inside a cell.
- Usually activated by the binding of a primary messenger to a cell surface receptor.
(e. g cAMP)
What does adenylate cyclase do?
Converts ATP to cyclic AMP (cAMP)
