Homeostasis Flashcards
Define homeostasis
Maintenance of a constant condition in the internal environment within narrow limits
Why is it essential ?
Enables survival in variable conditions - extra cellular conditions stable so metabolism occurs at optimal conditions.
Optimum conditions for Na + and K+ conc. , osmolarity , pH and temp
NO NEED TO LEARN
145 mM
4mM
300 mOsm
7.4pH
36.2-37.5 Celsius
4 components of homeostasis
Variable - change
Sensor - detects change - receptor or channel
Integrator- controls effector
Effector - works via negative feedback
What are the control systems of… glucose, temp, osmolarity, BP, o2 and co2, ph
Pancreas, gut, liver
Skin, skeletal muscle, hair
Kidney, thirst
Heart, vascular urge
Lungs, blood
Lungs, kidney
What’s the set point in bio systems
Set of ‘normal’ values
What are dual effectors also called? What are they?
Antagonistic effectors
Increase precision of homeostatic control - not all or nothing - constant interplay in normal range
Diabetes 1 vs 2
1 = inability to produce sufficient insulin ,glucose not converted to glycogen
2= insulin resistance
What are the following functions affected by?
Signalling
Intracellular communication
Input
Output
Density
Location
Affinity
Ligand conc.
Define endocrine
Paracrine
Autocrine
Hormones in blood
Signalling between near-by target cells
Cell secretes hormone - chemical messenger - binds to receptors
Preoptic area ?
Thyrotropes ?
1) in hypothalamus - regulates temp and sleep
2) TSH producing endocrine cells in anterior pituitary gland
What’s the Incretin effect?
Anticipatory change where insulin is secreted due to forward signals released prior to eating - readying the GI tract.
Define positive feedback and give an example.
Not part of homeostasis - destabilise - accelerate transitions between states - amplify signals
E.g. release of oxytocin during contractions of uterus during labour
When are negative feedback loops disabled?
In extreme conditions
