Homeostasis Flashcards
What percentage of the extracellular fluid does the Interstitial Fluid make up?
80
What percentage of the extracellular fluid does the plasma make up?
20
What happens if there is failure of capillary perfusion (i.e the plasma proteins get through)?
Gangrene
What percentage of body weight does water make up?
60
What ratio demonstrates how ECF contributes to Total Body Water?
1/3 (approx 14L)
What ratio demonstrates how ICF contributes to Total Body Water?
2/3 (approx 28L)
Why are females ‘less wet’?
they have a higher proportion of body fat, which has less water content than muscle
Water make up of muscle
70% water by weight
Water make up of fat
10% water by weight
What is meant by ‘homeostasis’?
maintenance of constant conditions in the internal environment of an organism
Briefly describe the mechanism of Negative Feedback Control.
- a controlled variable changes in its magnitude
- this is sensed as a stimulus to a receptor
- this information is fed to an integrating centre where it is compared with a reference level
- any difference between the actual and reference level generates an error signal which is fed to an effector mechanism which will bring about the changes to produce a response to counteract the change
What is Feedforward control?
A sophisticated negative feedback mechanism by which additional receptors permit the system to predict change and activate responses earlier. e.g temperature receptors in our skin
What is Positive Feedback?
an initial disturbance sets off a train of events that lead to an even greater disturbance
How do you calculate the volume of distribution in association with the dilution principle?
Dilution principle: c=m/v v=m/c
calculate the mass left in the body (i.e that has not been excreted) and divide this by the concentration in the test fluid
What 3 compartments of water can be measured directly?
- Plasma Volume
- Extracellular Volume
- Total Body Water
