Homeostasis Flashcards
% of ECF is ISF?
80%
% of ECF that is plasma?
20%
What happens if capillary perfusion fails and plasma proteins enter the tissue?
Gangrene
What ratio of TBW is ECF?
1/3
What ratio of TBW is ICF?
2/3
Why do females have less TBW on average?
- Higher proportion of body fat
What % of muscle is water?
70%
What percentage of fat is water?
10%
Define homeostasis?
The body’s ability to maintain a constant internal environment
What is the process negative feedback control?
- Change detected as a stimulus by a receptor
- Information sent to an integrating centre
- Integrating centre compares the stimulus to a reference level
- Magnitude of difference sent to an effector as an ERROR signal
- Effector responds equally opposite to fix
Feedforward control?
- Body “predicts” a change before it happens
- Pre-emptive
Positive feedback?
- Initial change from reference leads to even greater disturbance
- Think like exponentials
What is the dilution principle?
c=m/v
What does the dilution principle allow you to calculate in the body?
Volume of distribution
What must be taken into account before using the dilution principle?
- Volume that has been excreted
What 3 water compartments can be measured DIRECTLY?
- Plasma
- ECF
- TBW
How do you measure plasma?
Attach radioactive labels to plasma proteins
Why is plasma volume able to be measured this way?
Plasma proteins can’t move out of the plasma
What radioactive dye could you use?
Evans blue
What do you use to measure ECF?
Sucrose
What do you use to calculate TBW?
Radioactive water
