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BIOC33H3 Lecture Notes - Trachea, Cytosol, Aorta

Biological Sciences
Course Code
Stephen Reid

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BIOC34 Lec 6. Jan 22/14
Assignment #1 due Fri
SV regulation
o3 components:
Force of ventricular contraction - affected by sympathetic innervation,
leading to enhanced levels of Ca - lead to greater filament binding and
sliding  more contraction
Afterload (blood pressure ) - if BP is high, the ventricle is pumping against
a higher pressure - harder for ventricle to pump against this
High BP leads to lower SV because pumping against higher
pressure downstream
EDV - amount of blood in ventricle at end of relaxation phase
6 factors affecting:
Preload - pressure in vena system; if this pressure is higher, pushes
more blood in atria and ventricle - get higher ventricular filling
oVenus pressure pushing blood into ventricles
Ventricular compliance
oCompliance = ΔVolume / Δ Pressure  measure of how easily ventricle can stretch
or fill. Opposite is stiffness
High change in V for any change in P - have a compliant ventricle
oStiffness = Δ Pressure / Δ Volume
Small change in V for given change in P - heart will be stiff
Standard way in which seeing compliance curves
Normal curve: For any given change in P (0-10 ml of mercury), EDV goes
from 0-125 ml
With a less compliant lung that doesn’t stretch as easily, same change in P
leads to an EDV of 50 ml. on increased compliance curve, P=0-10, EDV=
Increased compliance leads to increases in V

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oEasier to take curve and flip axis around; easier to conceptualize
oWhen we flip axis around and plot V as a function of P, see that the increased
compliance curve has a higher curve and decreased compliance curve has a
smaller curve
oLower compliance = lower change of V for that given change in P
Skeletal muscle pump
oThis is the action of skeletal muscle contraction on veins and extremities that help
force blood up to the heart
oE.g. calf muscle
Vein running through
When this muscle is active and contracting, squeezes inward on vein and
forces blood upwards
Series of valves preventing blood from falling
When muscle contracts and forces blood goes upwards, there is an
increase in P in the vein moving upwards
Causes increase of P in upper region
This causes proximal valve (called proximal because it is closer to the
heart) to open. These valves are flaps of tissue. If pressure is closing
downward and pressure under valve is high, causes valve to open
In lower regions of leg, do not get blood falling backwards into ankle
because there is another valve at the bottom (distal valve) which is closed.
This is because we have a high pressure of blood in lower region, which
exerts pressure downwards that causes the valve to close downwards
Contraction of muscle forces blood to go upwards, opens valve and moves
blood towards the heart
Contraction of muscle puts pressure downwards and keeps distal valve
oIn varicose veins, stretched veins, valves are not able to open and close properly.
Blood pools and stretches veins further
Skeletal muscle pump
oWhen the muscle relaxes, there is no longer a build-up of pressure in the vein
because the muscle is not squeezing inward on it

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oLower pressure causes distal valve to open and it allows blood from the lower
regions (ankle, smaller venules) to flow upwards and into larger veins in between
the muscles
oLower pressure in the vein when muscle is relaxing, is not sufficient to cause
proximal valve to open, so proximal valve closes and blood cannot flow
backwards from the upper regions of the thigh back down into leg
During muscle contraction, blood is forced upward and when it relaxes,
more blood is able to flow to lower regions of leg and do not get back flow
because proximal valve is closed
oSkeletal muscle pump has been used for home therapeutic treatment to stop deep
vein thrombosis (blood clots) - important when on plane flights to walk around
every hour or so
oWaveform wrap allows blood to move from leg up to the heart
oSmall blood clot is not a problem; problem is when blood clots form and break
loose and travels up the vein towards the heart
oBlood clot forming and breaking up = deep vein thrombosis
Goes into atria, ventricle, gets lodged in a blood vessel in the lungs - are
very thin and small
Pulmonary embolism
oPulmonary embolism has many negative effects - blood is not flowing to that part
of lungs, tissues die. Blood clots lead to build-up of pressure since blood is not
flowing to parts of lung. Behind the clot, blood can’t flow and get fluid leaking
from blood vessels into lung tissue
Pulmonary edema
Inhibits gas exchange
Respiratory pump
oAct of breathing forces blood from abdomen into chest (inspiration) and from
vessels in the chest into the heart during expiration
oMajor respiratory muscle = diaphragm
Forms border between thoracic cavity/chest and abdomen
oWhen we inspire, diaphragm contracts and moves downward - causes chest to
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