Homeostasis Flashcards
What is the literal meaning of the term homeostasis?
Similar Condition
By what system are the majority of physiological responses controlled?
Negative Feedback
Describe negative feedback.
Magnitude of change of variable is monitored by a receptor
Info fed back to integrating centre
Compared to reference level
Difference between reference level and actual level generates signal
Signal fed to effector mechanism
This brings about a response which restores variable to reference level
What is the difference between negative feedback and feed forward mechanisms?
Negative feedback can only restore variable after change has occurred.
In feed forward mechanisms, an additional receptor can predict change to variable and activate a response earlier.
What is the difference between negative feedback and positive feedback mechanisms?
In negative feedback, a deviation from the reference level produces a response to restore conditions to optimum.
In positive feedback, a deviation from reference level produces a response which causes a greater deviation from the reference level.
Name the three compartments in which water exists in the body.
Intracellular fluid
Interstitial fluid
Blood Plasma
What proportion of TBW is generally found in ICF?
2/3
What proportion of TBW is generally found in ECF?
1/3
What is the average volume of water found in the body? i.e. TBW volume
42L
What percentage of the ECF is ISF?
80%
What percentage of the ECF is plasma?
20%
What is the main difference between blood plasma and ISF?
The presence of plasma proteins in plasma and their absence in ISF (as plasma proteins are too large to pass through the capillary wall)
Why are females considered ‘less wet’?
They have a higher proportion of body fat than males, which contains less water than muscle tissue.
What is the equation for dilution principle?
Conc.= Mass/ Vol.
Which three compartments of body water can be measured directly using the dilution principle?
TBW
PV
ECF
