Homeostasis Flashcards
What is homeostasis
A process whereby the body maintains a constant internal environment in which all processes work optimally
What is physiology
The study of how all the systems work together to maintain homeostasis
What is pathology
The study of illness and disease; it comes about when homeostasis fails
What happens to the body when it comes under threat?
Physiological mechanisms must counteract these potential threats to homeostasis
Describe negative feedback
It restores the regulated condition after its disturbance but cannot prevent it from happening
Describe feed-forward control
Additional receptors permit the system to anticipate change and therefore activate response earlier
Describe positive feedback
A mechanism which sets off a train of events that lead to an even greater disturbance. Such cycles lead to instability, and are rare in normal physiology but common in pathophysiology
What is water balance controlled by and why is it important?
Controlled by homeostasis, and important as it affects the concentration of everything else in the body
How much of body weight is made up by water
Around 60%
What 3 compartments is water storage split between
- intracellular fluid
- interstitial fluid
- plasma
What is the total volume of water in the body and how is it divided between the compartments?
Total volume of around 42L
2/3 ICF and 1/3 ECF
80% of ECF is ISF
20% of ECF is plasma
What is the equation for the dilution principle
v=m/c
Where:
V=volume
M=mass
C=concentration
What is one method of measuring plasma volume
Attach dyes or radioactive labels to plasma proteins as they cannot leave the cell
One method of measuring extracellular volume
Something that can cross capillary walls but not cell walls such as insulin or sucrose mannitol
There is only one thing that can be sampled directly, what is it and why?
Only plasma can be sampled directly, so only compartments where plasma is a component can be measured directly
