L18 - Cardiovascular System 1 Flashcards
What are the functions of the circulatory system?
distribution of dissolved gases and other molecules
circulating hormones
mediate inflammatory and host defense responses against invading organisms
conserve or release heat near skin surface
What type of circuit is the circulatory system?
parallel
What causes blood flow to decrease?
increased resistance which is caused by width, viscosity and length
What causes blood flow to increased?
increased difference in pressure, cannot flow if no pressure difference
What is tone?
basal state of muscle contraction in smooth muscle
What are adjustments from normal tone known as?
vasoconstriction and vasodilation
What is vasoconstriction caused by?
myogenic activity, O2, CO2, endothelin, sympathetic stimulation, vasopressin; angiotensin II, cold
What is vasodilation caused by?
myogenic activity, O2, CO2, nitric oxide, sympathetic stimulation, histamine release, heat
What is a myogenic response?
reflex constriction upon stretching of blood vessel walls and reflex dilation upon detection of lower blood flow
What is blood flow proportional to?
the pressure difference in a tube
How does blood flow in the capillaries compare to the blood flow in arteries and veins?
much slower due to huge cross-sectional area which facilitates exchange / diffusion
What is the structure of arteries?
very elastic
energy storage
What is the structure of veins?
less elastic
wider
expand easily - reserve
What is the structure of capillaries?
single cell thin
diffusion / exchange occurs here
What is bulk flow?
overall / mass movement of fluid between blood and interstitial fluid
What is absorption?
fluid movement form interstitium into capillaries
What is filtration?
fluid movement out of capillaries into interstitium
What is oedema?
interstitial fluid accumulation
The osmotic pressure attracting fluid absorption from the interstitium into capillaries is the result of what?
protein such as albumin
What is the composition of plasma and interstitial fluid?
almost equal solute concentrations
plasma = significant protein presence (albumin)
interstitial fluid = low protein presence
What pressures influence distribution between the capillary and the interstitial fluid?
osmotic pressure = due to solute concentration
hydrostatic pressure = pressure exerted by containment of fluid
Which end of a capillary does filtration occur? Why?
towards the arterial end
increased hydrostatic pressure
Which end of a capillary does absorption occur? Why?
towards the venous end
decreased hydrostatic pressure
