application of ohm's law to physiology Flashcards
define autoregulation
capacity of blood vessels to oppose changes in blood flow that are imposed by changed blood pressure
what are the physiologic mechanisms that explain autoregulation?
metabolic control and myogenic control
describe autoregulation via metabolic mechansim
increased pressure–> increased flow –> decr. metabolites or incr. oxygen –> incr. vascular resistance –>decreased flow
what is the myogenic control of vascular resistance?
via stretch-activated calcium channels, and other not well-defined mechanisms
describe autoregulation via the myogenic mechanism?
increased pressure –>incr. flow -> incr. stretch–> incr. Ca2+ activity –> incr. cytoplasmic calcium –> increased force–> decr. radius–> decr. flow.
which two vasodilators play an important role in edema induced by inflammation?
bradykinin and histamine
what induces the release of nitric oxide in normal tissues?
extracellular ATP and shear stress
what is rarefaction?
the process of decreasing the number of blood vessels
what are well-established angiogenic factors?
fibroblast growth factor, vascular endothelial growth factor, and angiogenin
what is hypertrophic vascular remodeling?
mechanism for the regulation of blood flow which involves the reduction of size of vascular lumen.
what are the causes of edema associated with capillary pressure?
heart failure; venous obstruction, inflammation (local vasodilation)
what are the causes of edema associated with interstitial pressure?
pulmonary - restrictive lung disease
what are the causes of edema associated with plasma oncotic pressure?
liver disease and malnutrition (reduced production), kidney disease (loss)
what are the causes of edema associated with interstitial oncotic pressure?
lymph obstruction, inflammation (increased permeability)
what are the causes of edema associated with permeability (inflammation)?
reduces reflection coef (raising interstitial oncotic pressure), increased surface area accompanying local vasoconstriction
