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
Where does ADH act on?
DCT and collecting duct
What three layers must filtrate pass through in the Bowmans capsule?
Blood endothelium
Basement membrane
Bowman’s capsule epithelium
