Homeostasis Flashcards
What is homeostasis?
The ability to maintain a relatively consant internal environment.
What is positive (+) feedb.?
AMPLIFIES AN INITIAL CHANGE
- allows large respone to develop from a small initial signal
- amplifies signal indefinietly (ENDED BY a separate control mechanism)
What is the outcome of positive (+) feedb.?
ACCELERATED RATE OF CHANGE
UNSTABLE
“EXPLOSIVE”
What are examples of positive (+) feedb.?
–Blood clotting
(stim. of platelet aggregation)
–Ferguson reflex
(giving birth - baby’s head in canal)
What happens when blood glucose becomes too low (hypoglycemia)?
CNS dysfunction -‐
brain cells almost exclusively use glucose for energy therefore hypoglycemia
Dysfunction and damage to retina, germinal epithelium and RBCs -‐
glucose is also the only nutrient used by these cells
What happens when blood glucose becomes too high (hyperglycemia)?
Cellular dehydration and damage –
ultimately leading to circulatory failure &/or renal failure
The pathogenesis of Diabetes Mellitus ( (-)f.b diagram)
[for blood glucose regulation]
X through Input, Output and Response
THUS, homeostasis always disrupted!
The pathogenesis of Rickets ( (-)f.b diagram)
[for blood Ca regulation]
X through 1 25 Vit D3, Gut and Response
THUS, homeostasis always disrupted
What is Rickets?
Loss of bone density due to lack vit. D3 or its actions
- gives rise to osteomalacia & blending of the long bones due to decreased strength
- severe cases result in poor development of teeth, with increased risk of caries.
What can happen when homeostasis is not achieved?
Pathological conditions with severe consequences may arise!
