6.4 Homeostasis Flashcards
What is homeostasis?
A self-regulating process in which a constant internal environment is maintained and regulated
What is negative feedback?
Change which counteracts changes back to normal limits
What is positive feedback?
Effectors respond to amplify a change away from the normal level
Why are multiple negative feedback systems more efficient?
- Gives more control as you can actively increase or decrease a level
- As opposed to simply switching on or off/ waiting for hormones to break down etc.
Factors that can influence blood glucose
- Eating
- Exercise
- Age
Usual blood glucose concentration
0.9 g/dm3
Where is insulin produced?
beta cells in the Islets of Langerhans in the pancreas
What processes does insulin promote?
Glycogenesis
What process does glucagon promote?
Glycogenolysis + Gluconeogenesis
Insulin actions
- Increases glucose permeability of muscle cells
- Activates enzymes in the liver
- Increases rate of respiration
Glucagon actions
- Activates liver enzymes
- Decreases rate of respiration
Adrenaline processes
- Activates glycogenolysis and inhibits glycogenesis
- Activates glucagon production and inhibits insulin production
Which cells does insulin bind to?
Muscle cells + liver cells
Which cells does glucagon bind to?
Liver cells
Which cells detect changes in glucose blood conc. ?
Pancreas cells
What is GLUT4?
Glucose channel protein
Where is GLUT4 found?
Skeletal and cardiac muscle cells, stored in vesicles in cytoplasm
Describe the action of adrenaline and glucagon
- Secondary messenger = cAMP
1) Bind to protein receptors on cell membrane
2) Activates attached enzyme = adenylate cyclase
3) Activated enzymes converts ATP into cAMP = a chemical signal
4) cAMP activates protein kinase A
5) Activates a cascade which breaks down glycogen
What is type 1 diabetes?
- Inability to produce insulin
After eating blood glucose remains high
How can type 1 diabetes be treated?
Eating regularly and eat simple carbohydrates - avoid sudden rise in glucose conc.
Insulin pump - regular insulin injections
What is type 2 diabetes?
- Insulin insensitivity
beta cells don’t produce enough or no response to insulin
resting blood glucose conc. too high
How can type 2 diabetes be treated?
Healthy exercise, lose weight, regulate carbohydrate intake
What reagent is used in colorimetry of glucose solutions?
Quantitative Benedict’s reagent
- Doesn’t produce yellow or green intermediate colours but uses shades of blue which can be detected
How is water potential monitored and acted upon?
Osmoreceptors in the hypothalamus which send a signal to the posterior pituitary gland which secretes ADH into the blood stream
