homeostasis Flashcards
define homeostasis
maintenance of a constant internal environment in which all processes work optimally
explain importance of maintaining constancy of internal environment
failure to adequately correct imbalances results in illness and disease, or pathology
eg diabetes occurs when body is no longer able to maintain optimum blood glucose conc
describe negative feedback control
when homeostatically regulated condition is sensed to have shifted from normal range, a signal is generated that produces response, that corrects the original disturbance and brings the regulated condition back within normal range
removes trigger that started response
size of response proportional to size of disturbance
explain feed forward control
additional receptors permit system to anticipate change and therefore activate response earlier
illustrate homeostasis by outlining daily water balance in man
plasma - 3L
ISF - 11L
—- therefore ECF = 14L
ICF - 28L
gains - total mls/24hrs = 2550
losses - total mls/24hrs = 2550
identify body fluid compartments
intracellular fluid (ICF) interstitial fluid (ISF) (fluid between cells) plasma (fluid component of blood)
ISF and plasma make up extracellular fluid (ECF)
explain importance of nature barriers separating body compartments
blood vessel capillary wall - plasma - ISF
- permeable to everything but plasma protein and blood cells
cell membrane - selectively permeable - ISF - ICF
define dilution principle
c = m/v therefore v = m/c
ONLY plasma can be sampled, therefore, only compartments of which plasma is a component can be measured directly (plasma, ECF , TBW)
nature of barriers which separate compartments is crucial in determining test substance
compartments measured directly and how to measure them using dilution principle
plasma volume - since plasma proteins cannot cross the capillary walls, can use dyes or radioactive labels that attach to plasma proteins - I125 albumin
ECF - something freely crossed capillary walls, but not cell membranes
eg insulin, sucrose, mannitol, which are all too large to cross cell membrane
TBW - no barrier to water in body, loading dose of heavy water/deuterated water (D2O)
may need to calculate indirectly
ISF = ECF-PV, ICF = TBW-ECF
outline role of each major system in maintaining health and optimal homeostasis
nervous & endocrine & msk - seek, supply and access nutrients
resp - supply O2
alimentary - breakdown food into usable forms and absorb across gut wall into bloodstream
cardio - transport O2 and nutrients via the bloodstream to the cells and transport CO2 and waste from cells to resp, GI, renal for disposal
nervous and endocrine coordinate and control all systems
INTEGRATION
define aetiology
cause of disease
define pathogenesis
how it develops
define symptoms
what patient feels
define signs
our observations
define diagnosis
process of determining nature of illness or other problem by exam of symptoms
