Homeostasis Flashcards
Osmoregulation: What does an increase in water potential of blood lead to?
1) Detected by osmoreceptors
2) Less ADH released from posterior pituitary gland = less ADH able to bind to receptors on cell surface membrane
3) Collecting duct walls become less permeable
4) Less water reabsorbed into blood = more urine
5) Decreasing water potential in blood
Osmoregulation: What does a decrease in water potential of blood lead to?
1) Detected by osmoreceptors
2) More ADH released from posterior pituitary gland
3) Collecting duct walls become more permeable
4) More water reabsorbed into blood = less urine
5) Increase in water potential of blood
Where are osmoreceptors?
Hypothalamus (Brain)
What does ADH cause?
Makes a person lose water via urination
What is ADH?
Anti-Diuretic-Hormone: Increases the aquaporin in the cell surface membrane of the collecting duct.
Which substances can travel into the filtrate?
Everything besides plasma proteins, as the basement membrane doesn’t allow larger molecules to be absorbed.
What is the glomerulus?
Network of capillaries
What is reabsorbed in the PCT?
Mineral Ions (Na-. Cl etc) , Vitamins, Amino acids via co-transport.
Where is the Glomerulus?
In the nephron
Where does selective reabsorption occur?
In the PCT
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.
Leading 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?
Pancreas
Glycogenesis
When blood glucose concentrations are too high, liver cells produce enzymes converting glucose to glycogen which is then stored n the liver cells.
Gluconeogenesis
When blood glucose conc is too low, liver cells also form glucose from glycerol and amino acids.
Glycogenolysis is…
When blood glucose conc is too low, liver cells produce enzymes that break down glycogen in the cells to glucose.
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.
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 receptors on the liver cell membrane inducing two reactions:
Activation of glycogenolysis and inhibition of glycogenesis
Alsom promotes secretion of glucagon from the pancreas and inhibits secretion of insulin.
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)
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)
