Homeostasis 2 (Hamzah) Flashcards
2 key components to reflex pathways
response loop and feedback loop
reflex pathway: response loop? feedback loop? (describe what happens)
starts with stimulus, ends in response of target tissue: sensor monitors environment, afferent signal to integrator when alerted by a change, integrator evaluates signal wrt set point, issues efferent signal, and response feeds back to the input
limiting factor of homeostatic control mechanisms is? result?
lag time before response and feedback = produce oscillations around the set point
positive feedback loops are not ___? what do they do?
not homeostatic: reinforce a stimulus and so the regulated variable is sent farther and farther away from the setpoint
cannon’s fundamental principles of homeostasis
NS aids in preserving fitness of internal environment. some body systems are under tonic control. some body systems under antagonist control. one chemical signal can have different effects in different tissues
fitness: def? NS aids in preserving what things?
conditions compatible with normal function: blood volume, osmolarity, blood pressure, body temperature
tonic control is an example of what type of control?
proportional aka tiny constant adjustments
examples of antagonistic control
insulin and glucagon. sympathetic and parasympathetic neural control
approximate volumes of fluid intake
intake: 2100 mL/day ingestion, 200 mL/day synthesis
approximate volumes of fluid output
resp tract, skin diffusion 700 mL/d. sweat very variable. feces 100 mL/d. water also lost from kidneys (excretion)
primary means of regulating fluid output?
renal excretion: anywhere from 0.5L to 20L per day
total body water is how much? distribution of fluid?
total body water is 60% body weight. 2/3 intracellular, 1/3 extracellular. most of extracellular is interstitial. 1/4 is plasma. a little bit of transcellular fluid.
total body fluid variation?
varies with age, sex, obesity. more fat = less water
intracellular fluid: % body weight? what comprises it?
28L or 40% body weight. cell fluid an individual mix of constituents
extracellular fluid: what? % bwt?
all fluid outside cells = plasma, etc. 20% bwt ~14L
extracellular fluid: continuous exchange with? via?
continuous substance exchange with interstitial fluid. via capillary membrane poors
what determines fluid distribution between compartments
balance of hydrostatic (pressure of a fluid) and osmotic pressures (from dissolved solutes like proteins)
most of total osmolarity of body fluids due to? ICF?
80% total due to Na and Cl. intracellular fluid osmolarity due to K
edema: what? source?
excess tissue fluid: mainly ECF, but can also involve ICF
