Topic 6C - Homeostasis Flashcards
What is homeostasis?
The mechanisms involved in the maintenance of a stable internal environment
What factors affect enzyme activity?
Temperature
pH
Blood glucose concentration
What is negative feedback?
Mechanism that restores the level to the normal
How does negative feedback work?
Normal level
Level changes from normal
Receptors detect change
Communication (via nervous or hormanal system)
Effectors response
Level brought back to normal
Why is having multiple negative feedbacks important?
Means you can actively increase or decrease a level so it returns to normal
Why is one negative feedback bad? (2)
Slow response
Less control
What is positive feedback?
Amplifies a change away from the normal
How does positive feedback work?
Normal level
Normal level changes
Receptors detect change
Communication (via nervous or hormonal system)
Effectors respond
Change is amplified
Why is positive feedback useful?
Positive feedback is useful to rapidly activate processes in the body
What organ controls blood glucose concentration?
Pancreas
What are the 2 hormones used when controlling blood glucose concentration?
Insulin
Glucagon
What type of cells secrete insulin?
B cells
What type of cells secrete glucagon?
A cells
What is the process converting glycogen into glucose?
Glycogenesis
What hormone activates glycogenesis?
Insulin
What is the role of insulin?
Lowers blood glucose concentration when its too high
What is the process called when glycogen is broken down into glucose?
Glycogenolysis
What is the process when glycerol and amino acids are broken down into glucose?
Gluconeogenesis
What hormone activates glycogenolysis?
Glucagon
What hormone activates gluconeogenesis?
Glucagon
What is the purpose of glucagon?
Raises blood glucose concentration when its too low
How does negative feedback mechanisms control the rise in blood glucose concentration? (6)
Normal blood glucose conc
Rise in blood glucose conc
Pancreas detects change
Secretes insulin, stops glucagon secretion
Liver and muscle cells respond by:
Cells take up more glucose
Glycogenesis is activated
Cells respire more glucose
This causes blood glucose concentration to fall
How does negative feedback mechanisms control the fall in blood glucose concentration? (6)
Normal blood glucose conc
Fall in blood glucose con
Pancreas detects change
Pancreas secretes glucagon, stops insulin secretion
Liver cells respond:
Glycogenolysis is activated
Gluconeogenesis is activated
Cells respire less glucose
What are glucose transporters?
Channel proteins that allow glucose to be transported across a cell membrane
What occurs when insulin levels are low? (Glucose transporters)
GLUT4 stored in vesicles of cytoplasm
Insulin binds to receptor on the cytoplasm membrane, triggering movement of GLUT4 to membrane
Glucose enters the cell via facilitated diffusion
Where is adrenaline secreted from? Why is it secreted?
Adrenal glands
When there is a low conc of glucose in your blood, when your stressed or when you’re exercising
How does adrenaline increase blood glucose concentration? (2 ways)
Activates glycogenolysis
Inhibits glycogenesis
What is the second messenger model?
Binding of hormone to cell receptors activates an enzyme on the inside of the cell membrane which produces a second messenger
What does the second messenger do?
Activates other enzymes in the cell and brings about a response
How is glycogenolysis activated?
Adrenaline and glucagon bind to their receptors and activate the enzyme adenlyate cyclase
What does adenylate cyclase do?
Converts ATP into cyclic AMP (cAMP) (which is a second messenger)
What does cAMP do?
Activates an enzyme called protein kinase A
What does protein kinase A do?
Activates a cascade that breaks down glycogen into glucose
What is diabetes?
A condition where blood glucose concentration cant be controlled properly
What is type 1 diabetes?
Immune system attacks the b-cells in the islets of langerhans so they can’t produce any insulin
After eating, the blood glucose level rises and stays high
The kidneys cant re absorb all the glucose so some of it is secreted in urine
What is hyperglacaemia?
When after eating the blood glucose level rises and stays high
How can you get type 2 diabetes?
Often linked with obesity, lack of exercise, age and poor diet
What is type 2 diabetes?
Occurs when b-cells dont produce enough insulin or when the body’s cells dont respond properly to insulin
Why would the body’s cells not respond properly to insulin? What is the effect of this?
Because the insulin receptors on the cells membrane dont work properly, meaning the cell can’t take up enough glucose
Means that the concentration of blood glucose is higher than normal
How can type 2 diabetes be treated? (5)
Healthy, balanced diet
Losing weight
Regular exercise
Glucose-lowering medication can be taken aswell as insulin injections
How can you determine the concentration of a glucose solution? (3)
Using colorimetry
Perform a quantitive benedicts test
After this, use a colourimeter to determine the light absorbance
The higher the concentration of glucose, the more blue will have been lost, decreasing the absorbance of light
What is ultrafiltration?
As blood passes through the capillaries in the cortex, substances are filtered out of blood and into long tubules that surround the capillaries
What is selective reabsorbption?
Useful substances, such as glucose and the right amount of water, are then re absorbed back into the blood.
The remaining unwanted substances pass along to the bladder and are excreted as urine
What are nephrons?
Long tubules along with the bundles of capillaries where the blood is filtered
