Homeostasis Flashcards
who came up witht the rough idea of homeostasis and in what year?
Claude Bernard
1859
what was Bernards orignal idea?
“consistancy of the internaal environment is a requirement of free-living animals”
in what year and by who was the term homeostasis coined?
1929
William B. Cannon
Define homeostasis
the control or stabilisation of the internal environment
what are confomers?
conformers are organisms that are restricted to more constant environements (reptiles need heat to warm up)
what are regulators?
organisms that are able to control their internal environment and therfore can exploit physiologically hostile and variable environments
what percentage of the body is intracellular fluid (ICF)?
67%
what percentage of the body is extracellular fluid (ECF)?
33%
what 3 things is extracellular fluid divided into? what are the percentages?
-plasma (8%)
-interstitial fluid (fluid surrounding organs) (24%)
-transcellular fluid (1%)
why is extracellular fluid more important than intracellular fluid?
ICF as cells have membranes to help maintain their environment, whereas ECF if fully interchangeable with the outside world
what are the 8 factors that affect the internal environment?
O2
CO2
Na+
K+
Ca2+
Glucose
Blood pH
Temperature
what does the inability to regulate the internal environment cause?
ill health or death
how do some microorgansisms cause infectious diseases?
by disturbing the internal environment
(e.g. cholera toxin stimulates Cl- secretion into the lumen of the intestines)
What are O2 levels controlled by and how?
-Controlled by haemoglobin.
-Hb has a high affiniyty for O2 and only releases when the local concentration is low
what does respiration control and how?
-[CO2]
-hyperventilation decreases plasma [CO2]
-hypoventilation increases plasma [CO2]
