homeostasis revision Flashcards
negative feedback control
when a condition becomes abnormal it generates a signal which causes a response that regulates the condition back to normal
and the initial signal gets turned off by the response
body functions that use negative feedback
temperature- sweating/shivering
a cheracteristic of negative feedback
can’t prevent disturbances but fixes them
feed forward system
like negative feedback but predicts change so response is earlier
positive feedback
sets of a chain of events
e.g in nerves- Na+ enters cells which then lests more Na+ in
amount of water in body
42L
water in ECF
14L
3L in plasma and 11L in interstitial
water in intracellular
28L
capillary walls are permeable to
everything except plasma proteins and RBC
when you drink water or administer a drug that can pass cell membranes how does it get distributed?
and example of substance
⅓ ECF: ⅔ ICF
measurement of body fluids: what can be directly measured
plasma and its compartmens:
ECF and total body water
how to calculate using dilution principle
V(of body fluid)= m(amount of substance inserted*)/ c(conc of substance used)
*minus any that gets excreted or metabolised
substance used to calc plasma volume
plasma proteins with dyes or radioactive labels
(won’t pass into capillary)
evans blue or I125 albumin
substance used to calc ECF volume
something that won’t pass into cells but will stay in plasma and intertsitial
inulin, sucros, mannitol
24NA+ or 36CL-
substances used to calc total body water
no barrier to water
heavy water/ denatured water (D2O)
