Homeostasis Flashcards
Homeostasis
The maintenance of a relatively constant internal environment
Factors that need to be kept stable
Intersitial fluid plasma
Ph
Temperature
Hormone levels
Blood gases such as o2 or co2
Normal levels of potassium
3.5-4.5 mM
What’s considered Hyperkalaemia
Concentration of k+ ions exceeds 5.0mM
Above what concentration of K+ is considered a medical emergency
6.5mM
Elements of a control centre
-detector
-comparator/control centre
-effectors which make a change such as a muscle contraction
Regulated variable
Sensor exists to keep this variable within limits
Non regulated variable
Can change to achieve control of regulated variable. Eg Herat rate changing which affects blood pressure
Equation for dissociation of co2
Co2 +h20=h202=h+ +hco3-
Examples of pyrogens
Eg bacteria
Positive feedback mechanism
Amplifies the change eg child birth, the fetus pressing the cervix causes afferent signal to the hypothalamus which caused the secretion of the oxytocin by posterior pituitary causing more contractions.( positive reinforcement|)
Feedforward
Limits change
Anticipatory behaviour =acts to minimise disruption to set points
What does loss of homeo stasis results in
Disease
Negative feedback example
Sensors such as carotid and aortic baroreceptots detect change
Comparator such as brain stem and The nucleus of the tract is solitarius
Effectors such as cardiac or smooth muscle result in vasoconstriction and incresed co which reduces body pressure back to 120/80