B16 - Homeostasis Flashcards
What is homeostasis?
Homeostasis is the regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes
What does a negative feedback loop do?
It counteracts a change, bringing the value of a parameter—such as temperature or blood sugar—back towards it set point
What does a positive feedback loop do?
The feedback causes the corrective measures to remain turned on. The system deviates even more from the optimum level. Stops when there is no more stimulus
What occurs in the second messenger model using adrenaline as the hormone?
Adrenaline binds to its receptor on the target liver cell
Receptor changes shape activating adenyl cyclase
Activated adenyl cyclase converts ATP to cAMP
cAMP binds to protein kinase, changes its shape, and therefore activates PK, which will convert glycogen into glucose. Glucose leave cells by facilitated diffusion
What is the role of the pancreas?
Produces digestive enzymes (protease, amylase and lipase) as well as hormones (insulin and glucagon)
Where in the pancreas are hormones produced?
The islets of Langerhans, containing α and β cells
What does the liver do?
Stores glycogen and produces bile and urea
What does glycogenolysis do?
Turns glycogen into glucose
What does glycogenesis do?
Turns glucose into glycogen
What does gluconeogenesis do?
Glucose is formed from sources other than carbohydrates, e.g. amino acids and glycerol
What is the role of insulin?
Increases uptake of glucose into cell so lowers blood glucose concentration
What cells detect a rise in blood glucose concentration so secrete insulin into blood plasma?
β cells
What is the mechanism of insulin?
Insulin binds to receptors on the C.S.M, which makes the glucose transporter carrier protein (stored in vesicles) move up to the cell membrane where they fuse, so glucose enters the cells via facilitated diffusion
What is the role of glucagon?
Convert glycogen into glucose
What cells detect a fall in blood glucose concentration and secrete glucagon into blood plasma?
α cells
What is the mechanism of glucagon
Glucagon binds to receptors on liver cells and activate enzymes which convert glycogen into glucose (second messenger model)
Binds to its receptor on the target liver cell
Receptor changes shape activating adenyl cyclase
Activated adenyl cyclase converts ATP to cAMP
cAMP binds to protein kinase, changes its shape, and therefore activates PK, which will convert glycogen into glucose. Glucose leave cells by facilitated diffusion
What is diabetes?
Diabetes is a metabolic disorder caused by the inability to control blood glucose concentration. It is either due to lack of insulin or loss of responsiveness to insulin
What is the glucose tolerance test?
After 8-12 hours of fasting prior to test, the patient is given a drink with 75g glucose in it. Blood glucose levels are then monitored at regular intervals or in a single test after 2 hours. It should then come down over time to a normal level showing insulin works
How can diabetes be diagnosed?
Test strips allow rapid clinical diagnosis or home monitor of blood glucose levels
Urine dipsticks detect glucose in urine sample
“Pinprick” test fingertip is pricked with needle, the test strip monitor blood glucose levels
What is type 1 diabetes?
Insulin dependent diabetes, the body is unable to produce insulin. Lack of insulin results in less glycogen stored in the liver and dangerously high blood glucose level that can lead to serious organ damage
How does type 1 diabetes occur?
Genetic causes, could be result of an autoimmune response: the patient’s own immune system destroys the 𝜷 cells in the islets of Langerhans
Develops in childhood usually in a few weeks, with the sign and symptoms being obvious
How is type 1 diabetes treated?
It is controlled by having a good diet and exercising, insulin injections
Injection not pill as insulin is a protein and would be broken down in the stomach
The dose of insulin matches the amount of glucose consumed so biosensors and insulin pumps monitor blood glucose levels and adjust dosage of insulin
What is type 2 diabetes?
Insulin independent diabetes and it is much more common than type 1
The glycoprotein receptors on the cell surface lost their responsiveness to insulin. It can also be a result of inadequate insulin supply from pancreas
How does type 2 diabetes occur?
Starts at older age, develops much slower. Symptoms are less severe so it can remain unnoticed
Over-eating, obesity and lack of exercise are causing increasing numbers of cases in younger people
