Homeostasis (non kindey) Flashcards
Define Homeostasis?
Maintenance of a constant internal environment within set limits.
Three factors to regulate on spec?
Temperature, pH, Water potential.
General features of a homeostatic system?
Receptor: detects stimuli/ change in environment
Controller/coordinator: contains set limits.
Effector: carries out corrective measures.
Positive Feedback?
Amplifies the change to stray further from set limits. E.g sodium ions in action potentials.
Negative Feedback?
When something changes the opposite effect is instigated to return back to the norm level.
Insulin mechanism?
Binds to protein receptor on target cell.
Causes vesicles with carrier proteins embedded in the membrane to fuse with the cell surface membrane.
Expresses more carrier proteins on CSM.
Allows Facilitated diffusion of glucose into the cell to be converted to glycogen.
Glucagon action (second messenger adrenaline)?
Glucagon binds to transmembrane protein receptor of a target cell.
Causes a change in shape inside the membrane activating adenyl cyclase.
Adenyl cyclase converts ATP to cAMP, which acts as a second messenger.
cAMP activates kinase through a change of shape.
Kinase catalyses glycogen to glucose.
Glucagon action (simplified results in second messenger)
Glucagon binds to receptor on CSM of target cells.
Activates enzymes involved in hydrolysis of glycogen to glucose.
Activates enzymes involved in conversion of glycerol and amino acids into glucose.
Name the two processes that occur when blood sugar is low?
Glycogenolysis
Gluconeogenesis
Name the two processes that occur when blood sugar is high?
Glycolysis
Glycogenesis.
Explain why it is important to maintain a constant internal environment?
Maintains optimum conditions for enzyme catalysed reactions.
Ensure glucose is available to all cells for respiration.
Maintain water potential of tissue fluid so excess water us not lost or gained, avoiding damage.
Describe what happens after a meal after glycogen has been produced (blood sugar low)
If glucose conc falls too low, this is detected by the pancreas.
Pancreas releases glucagon from alpha cells from the islets of langerhans.
Glucagon causes the liver to hydrolyse glycogen stores to glucose, diffusing back into the blood.
Increases blood glucose, ceases secretion of glucagon.
Describe what happens soon after a meal (blood sugar)
Glucose absorbed from intestines through hepatic portal vein.
Blood sugar increases, detected by pancreas.
Pancreas secretes insulin from B cells in the islets of langerhans.
Insulin causes glucose to be taken up by the liver and converted to glycogen.
This reduced blood glucose, ceases secretion of insulin.
Explain how you could produce a dilution series of glucose and use to estimate the concentration of glucose in the urine of the patient
Produce a dilution series from a known glucose stock solution by adding set amounts of water.
For each solution add benedict’s solution and heat to 95 degrees for 5 mins.
Use colorimeter to measure absorbance of each sol.
Plot a calibration curve absorbance against conc.
Repeat benedict’s test on urine sample, use calibration curve to estimate conc.
