Feb 27 , 2012 Lecture Monday
Risks associated with high intensity excericse
Periodic elevation in systolic mean arterial pressure that
occurs with a single repetition of high intensity excericse
-Valvsalva Maneuore pressure is directly transferred to the
arteries iwthin the thorax.
Risk Factors associated
--See the posted images on moodle.
Immiediate risk, Catatrophic failure refer to as aneurysms
(the wall of the artery rupture)
Pic on the left shows the ripped aorta. Blood penetrates
wall of aorta. Wall becomes stretch out and becomes
weaker since the blood has penetrated in it.No longer
strucutural strong, therefore aorta balloons out, the weaker
the wall becomes and it can lead to RUPTURE.
This rupture is deadly, since this is aorta.
Aneurysm of aorta (not likely to occur in young
individuals, unless genetic predispotion of having no
stronger aortic walls (Marfan Syndrome: which is genetic defect in one of the protein that helps build elastin and
lamale(encircle the aorta. Without the protein aorta will
most likely to rupture since its not very strong.
One of the location of Aneurysm more commin in aged
individuals is in the abdoiminal region of Aorta .
More common to occur when u get older over 60 , mostly
in males than females.
It comes down to having disruption in the structure of and
disregulation in the amount of elastin that is being
distrubted throughout the wall of produced. You can
having nothing produced or too much being
degraded(protelysed)
That leaves wall of aorta much more susceptible to having
tears.
If you start to develop aneyruym like this , first treatment is
done with the blood pressure (meaning its reduced).
They wait to see if the wall can be repaired itself in low
pressure.
Another risk is
1. Myocardial Infarction (Heart attack)
Left ventricle has to work against the pressure in the aorta, in order to achieve stroke volume. LV has to create
pressure that exceeds aortic pressure in order to have
blood being ejected.
If you’re MAP, is really high 200mmHg, that means LV has
to exceed 200mmHg if it’s going to eject blood. LV can do
it if it contracts much more vigioursouly, much more
intense contraction, myocardial cells will use more oxygen
in order to generate ATP, that’s needed to sustain the
actin-myosin cross bridging. If LV does meet higher
pressure demand the myocardial cells will need more
oxygen to keep doing this, but if it doesn’t that means we
WOULD NOT HAVE STROKE VOLUME, SINCE THERE
WILL BE NO PRESSURE GRADIENT and BLOOD
WILL REMAIN IN THE LEFT VENTRICLE ( we will have
much reduced CARDIC OUTPUT (CO)
And as a result of Less CO , the myocardial cells will
receive much more oxygen.
Where does the oxygen come from that feeds the
myocardial cells? It’s not coming from the blood that is
sitting inside the ventricles, that blood is simply being
pumped from one location to another. The only way
myocardial cells receiving the nutrients they need is from
the CORONARY CIRCULATION (blood vessels that branch of aorta and circle the heart
and penetrate through the walls of myocardium to deliver
the nutrients and oxygen directly to the myocardial cells)
Reducing Cardiac Output you reducing the blood that is
going to circulate through the coronary circulation and
provide the oxygen to the myocardial cells.
So in either situation, either LV is meeting higher pressure
but utilizing more oxygen OR you are not meeting the
pressure and there is less oxygen being delivered.
There is a situation that is likely to occur where the oxygen
demand by the myocardial cells is not being met by the
oxygen being delivered. If the myocardial cells do not
meet the required oxygen that means they will not be able
to synthesize enough ATP to maintain their function.
The myocardial don’t store ATP they contiously use ATP.
Since they are active..
When they can’t synthesize new ATP? Contraction occurs
since cross-bridge cycling won’t be able to continue. Other
thing is the ability to maintain negative mem potential is
lost. Cells become dysfunctional as a result of that and
they will not be able to excited.
Starred myocytes : not being able to contract anymore *More likely to occur(myocardial infarction) in older
individuals than younger people since they are performing
high intensity exercises since blood vessels and heart are
quite resilient.
One other thing that makes it more likely to have heart
attack is if you couple the situation where you have very
high arterial pressure which your heart is working against ,
if you couple that with problems in your arteries (problems
in the coronary arteries)
Most common problem is (coronary artery disease) which
leads to formation of atherosclerosis plaques also
called atherosclerosis.
-Plaque is forming on in the inner surface of the artery
-It is the accumulation of both l of lipids, immune cells,
smooth muscle cells, collagen.
-Plaque can grow and develop into quite a large region
within the artery
-Structural impediment, small lumen space that has to get
blood flowing through it
-When you have sever atherosclerosis, blood does not go
to the regions that are downstream of the plaque since its
very high resistant location to get past.
-Less blood is capable of passing down into the smaller blood vessel and exchange oxygen with the heart.
-The other risk associated with atherosclerosis, the plaque
region down there in the picture can develop Thrombus
(platelets are globing on to surface of plaque since
they are attracted to the collagen that’s there).
--this enlargement could block the entire artery and other
potential danger is that the thrombus is not very stable
and as blood pushes against it, it is very likely that it could
break off and then its going to travel in the blood
downstream into smaller blood vessel where it could
totally block the blood vessels (embolus is the blockage
of smaller blood vessel)
If there is no blood getting past this point, and any cells
that are downstream of this, are going to be starved of
oxygen, real risk that can occur in heart, if it occurs it is
going to lead to regions that become oxygen starved that
could precipitate a heart attack. Same process occurs in
other locations in the body and you can have plaques and
thrombus forming in carteoid artery and if those thrombus
break lose they will go to blood vessels in the brain
leading to a STROKE.
Other locations where it’s common to have
atherosclerositic plaque are in the femeral and iliac artery
going into the leg and that can impair blood supply to your lower leg muscles.
--Focus on the consequences of the heart---
Coronary Arteries- Areas at Risk of Ischemia
Coronary arteries are branching off aorta,
A is the coronary artery (left) ; supplies left ventricle
B is the coronary artery (right) ; supplies Right ventricle
Initially start on the outer surface of the heart, and as they
branch into smaller arteries and then arterioles they are
penetrating and sitting in the walls of ventricle.
Because of their location they are susceptible to
something that puts them aside from all other arteries in
your body. Its due to their location within Wall of
Myocardium). Wall of myocardium is every minute
undergoing multiple periods of strong contraction followed
by relaxation.
The cardiac cycle puts stress on the coronary arteries.
Coronary Artery Blood Flow graph (top line is aortic
pressure purple(gives the idea of the interval systolic and
diastolic interval). Aortic pressure is the driving force for
moving blood through arterial circulation; you would
expect that flow should follow the pattern that you see with the aortic pressure.
Flow should be highest when the aortic pressure is
highest, coz that’s where the gradient of pressure from the
arterial to the venous side will be greatest
Red Line is the measure of blood flow through the
coronary artery. Left coronary artery that is supplying the
left ventricle we don’t see a complete pattern , we don’t
see higher flow when there is higher pressure.
During Diastole beings it rebounds, and slowly follows
down.
During Systole we have strong reduction, in the
beginning the flow goes to 0
throughout systole it remains low,
Aroun
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