Feb 15 , 2012 Lecture Notes Human Physiology II
Every organ in the body is filled with blood vessels
Extensive organ , if added all the vascular system it would circle the globe.
Corrosion craft of brain circulation (the image)
-Why do we need so many blood vessels?
-Responsible for delivery of oxygen (also other nutrients like glucose, free fatty acids, )
rich blood to all tissues within the body.
-Extensive system is needed to deliver these in a timely efficient way.
-Other functions of circulatory system:
(i)Temperature control (homeostasis, maintain 37C , 5L of blood, allows the heat to be
maintained within certain locations in the body. If you want to cool you send more blood to
peripheral (outer regions) like skin in order to increase heat exchange with environment)
(ii)Nutrient Delivery -
(iii)Removal of waste
(iv) Distribution of Hormones - also delivers hormones that are delivered in one location e.g
pituitary glands released into circulation)
(v) Transport of Immune cells- allows immune cells to get from one location to another
location so they can detect invasion of any bacteria or cell death.
Circulatory is not just passive transport system , very active in regulating blood at where its
Two different circulation
(i) Right side pumping to the pulmonary circulation
(ii) Left side pumping to the systemic circulation
Percentages listed show what percentage of blood coming out of left ventricle is going to each
of the locations.
Not equal division , not based on total mass either ( kidneys quite small receive 20% of cardiac
output) -Blood is distributed unevenly
-How is this regulation achieved ? How does the body enable certain organ to receive
more blood than the other organs?
--Resting Skeletal muscle vs Exercise Muscle
Different levels of blood will be delivered to the muscle depending on its need.
Heart plays an important role to modify the cardiac output depending on the situation
The vascular system also makes sure that you can make the demands of excercising muscle,
Just the heart increasing the cardiac output not enough, there has to be adapation within
the vascular system to allow that blood to get delivered to the excercising muscle not to
Flow= Pressure Gradient / Resistant
Flow= Q or F (apply to blood movement)
Blood moves from the left ventricle where its being pumped into the aorta, all through the
network of blood vessels, back to right atrium (Circuit that the blood is making through the
In order for it to go from aorta to the right atrium we need pressure gradient that will favour its
direction, our pressure gradient is MAP (mean atrial pressure found in aorta)
Q (Cardiac Output) = Mean atrial pressure – Right Atrial Pressure/ Total peripheral resistance
(summation of resistance of moving blood through every single blood vessel its going through)
In Normal Individuals RAP is 0mmHg. (Important to write it)
Q=MAP-RAP/ TPR but RAP is 0 therefore;
Q= MAP/ TPR
MAP is regulated by altering Q and TPR
Mean atrial pressure is high prority homestatic regulated factor.
What is it that determines MAP? Cardiac out put and TPR determine it
-Normal body has 100mmHg ( we need to keep it there)
-If somebody has low blood pressure and they faint and its because they had a change in
cardiac out put or total peripheral resistance. If body tries to MAP to prevent , it will have to
adjust Q & TPR (or both)
Principle Determinant of Flow
1. Effect of Pressure Gradient
The diff between .1 and .2 is important
Tubes are same size, diff are in pressure
P1 begnign , P2 End
Flow is going from left to right (since higher on left)
50-10= 40mmHg (delta pressure, driving pressure to make blood to go through that vessel)
-raised our inflow pressure
-greater changing pressure from P1 to P2
-Flow is going to be twice as gradient
90-10= 80mmHg (flow will be twice as greater since pressure gradient is very high)