cardiovascular Flashcards
functions of the cardiovascular system
Transportation of oxygen,
nutrients and metabolites to the
tissues, and the removal of
metabolic waste products.
Distribution of hormones to
the tissues, and secretion of
some hormones.
Involvement in homeostatic
mechanisms. Key role in the
regulation of body temperature.
what is the pulmonary circulation
the pulmonary circulation is connected to
the heart “in series”, which means that the
entire blood volume has to pass through it
every time it circulates the body.
what is the systemic circulation
the systemic circulation is connected to the
heart “in parallel”, which means that there is a
choice of which part of the body receive more
or less of the available blood volume.
Typical values (for an average person):
Total blood volume: ~5 litres (~7% body weight)
Cardiac output: ~5 litres/min
how these values impact the pulmonary system
It needs to accommodate the entire blood
volume every minute, even at rest.
During peak exercise it needs to accommodate
up to 5 times the entire blood volume (~25 litres)
every minute.
how these values impact the circulatory system
There is not enough blood to fully support the
metabolic needs of every tissue. Because of this,
blood supply to inactive tissues is reduced and
blood supply to active tissues is increased.
how is pressure created
Contractions of the ventricles of the heart generates pressure
which is transferred to the blood causing it to flow along the blood vessels.
DRIVING PRESSURE
(flow is created by the pressure difference between two points)
what is Poiseuille’s Law
𝑅𝑒𝑠𝑖𝑠𝑡𝑎𝑛𝑐𝑒 = 8𝐿𝜂 / 𝜋𝑟 power of 4
𝜂 = viscosity that we only need to consider in certain circumstances
𝐿=in the context of the cardiovascular
system we can ignore (does not change)
what is darcys law
FLOW = PRESSURE DIFFERENCE / RESISTANCE
how vessel radius impacts the resistance
Doubling the vessel radius
reduces resistance by a
factor of 16!
Halving the vessel radius
would increase resistance by
a factor of 16!
Flow relation to pressure and vessel radius is directly proportional.
This means that the higher the driving pressure and the larger the radius of a vessel,
the higher the flow is (and vice versa).
what is the Simplified Poiseuille’s Law
𝑅𝑒𝑠𝑖𝑠𝑡𝑎𝑛𝑐𝑒 = 1 / 𝑟 power of 4
Combining Darcy’s and Poiseuille’s Laws
FLOW = PRESSURE DIFFERENCE ΔP × r power of 4
how do you calculate the velocity of blood flow
velocity = flow rate / cross sectional area
The narrower the vessel, the faster the flow
units for the velocity equation
Velocity: distance/time (e.g. cm/min, m/sec, etc.
Flow rate: Volume/time (e.g. cm3/min)
Cross-sectional area: cm2, m2, etc.
