Lecutre 11 Flashcards
Capillary exchange
Movement of substances in and out of capillaries
Most important means of exchange
Diffusion
What affects the movement of fluid form capillaries
BP, Capillary permeability and osmosis
Diffusion in cappilaries
- lipid soluble cross capillary walls diffusion through plasma membrane
- water-soluble diffuse through intercellular spaces or through fenstatrions of capillaries
Net filtration pressure
Force responsible for fluid moving across capillary walls, two forces affect pressure
Hydrostatic pressure
physical pressure of blood flowing through
the vessels or of fluid in interstitial spaces
Osmotic pressure
movement of solutes (plasma or tissue fluid)
through a membrane (plasma membrane) in the presence of a non-
diffusible solute (large proteins); Large proteins do not freely pass
through the capillary walls and the difference in protein
concentrations between the blood and interstitial fluid is
responsible for osmosis
Net Filtration pressure equation
Net hydrostatic pressure minus net osmotic pressure
Net hydrostatic pressure equation
CHP - IFP = net hydrostatic pressure
CHP
capillary Hydrostatic pressure
IHP
interstitial fluid hydrostatic pressure
Interstellar fluid hydrostatic pressure
hydrostatic pressure exerted by the interstellar fluid of tissue surrounding the capillaries
Net osmotic pressure equation
BCOP-ICOP= Net osmotic pressure
BCOP
Blood colloid osmotic pressure
ICOP
Interstitial fluid colloid osmotic pressure
Venous veins function
return to the heart increases due to the increase in BV, Venious tone and arteriole dialation
Venous tone:
a continual state of partial contraction of
the veins as a result of sympathetic stimulation
What does gravity do to BP
In standing position it increases BP below the heart and decreases pressure above the heart
What does muscular movement do
improves veinous return
Local Control
Most tissues blood flow is proportional to metabolic needs of tissues
Nervous system
Responsible for routing blood flow and maintaining BP
Hormonal Control
Sympathetic action potentials stimulate epinephrine and norepinephrine
What do local factors do for capillary bed
Regulate metarterioles and precapillary sphincters
What does increased metabolism of a tissue result in
vasodilator substances (carbon dioxide, lactate, potassium)
What does vasodilator substance cause
Vasodilatation and relaxation of sphincters, blood flow increases to serve working tissue
Autoregulation of blood flow
Blood flow can increase 7 to 8 times as a result of vasodilation of metarterioles and precapillary sphincters in response to increased rate of metabolism
Vasomotion
period contraction and relaxation of precapillary sphincters
Long-term local control
capillaries become denser in a region that regularly has a increased metabolic rate
Nervous control of BF in tissures
- minute to minute regulation of local control
- provide means blood be shunted from one large area of the peripheral circulatory system to another by increasing resistance
- Sympathetic division most important innervates all vessels except capillaries, precapillary sphincters, and most metarterioles
Vasomotor center located
lower pons and upper medulla oblongata
Excitatory part
Tonically active, causes vasomotor tone- norepinephrine
Inhibitory part
Causes vasodilation by decreasing sympathetic output
Sympathetic stimulation of adrenal medulla
causes output of norepinephrine and epinephrine into circulation causes vasoconstriction in vessels
Vasomotor tone
constant sympathetic stimulation of vessels results in continual state of partial constrictio
