Systemic Circulation

Question 1

Define vascular compliance

Answer 1

Compliance = ΔV/ΔPtm
-where ΔPtm = transmural pressure = Pin - Pout

Metal tubes have low compliance, baloons have high compliance since they CAN blow up

Question 2

1) Describe the pressure-tension relationship/ equation on blood vessels.
2) Define tension

Answer 2

T=P×r

T = tension (force per unit length, dyne/ cm)
P= transmural pressure (dynes/cm2) 
r = radius (cm)

Tension is the amount of energy it takes to close a vessel that has been popped open or the amount of energy it takes to keep it closed. If tension increases too much in the aorta, ruptures or aneurisms can occur.

Tension decreases during stenosis due to decrease r.

Question 3

Know how arterial compliance changes with age and the effects on arterial pressure

Answer 3

VASCULAR COMPLIANCE DECREASES WITH AGE (see pg 11). Younger people have more compliant BV’s than older folks.

As you age BP changes due to increase in arterial volume & TPR.

Question 4

Describe the role of arterial compliance in storing energy for blood circulation

Answer 4

The artery stores some blood by virtue of its stretch, so than flow is never 0.

Question 5

Describe the factors that shape the aortic pulse contour

Answer 5

Pulse pressure. The opening & closing of the aortic valve has pressure implications downstream & we never see 0 flow because the aorta is compliant (Windkessel effect). This compliance (stretching of vessel holding the blood) allows us to have a diastolic blood pressure.

See pg. 14

Question 6

Describe the factors that determine wave propagation and explain the conversion to steady flow

Answer 6

The increase in flow in a rubber tube will be slower & more gradual than the metal tube because it is more compliant (since the rubber tube is distended & takes away some of the pressure). Even when pressure from the source driving flow is turned off (i.e., closing of the aortic valve), the rubber tube that expanded will contract (recoil) & force flow in the forward direction. So if you have a compliant vessel with intermittent pressures you will not have pressures that go down to zero. This is called the Windkessel effect of the aorta.

See highlighted propagation curve on pg. 13

Question 7

Define hydrostatic pressure

Answer 7

The pressure exerted by a fluid at equilibrium at a given point within the fluid, due to the force of gravity. Hydrostatic pressure increases in proportion to depth measured from the surface because of the increasing weight of fluid exerting downward force from above.

Question 8

Define vascular elasticity

Answer 8

Elastance = 1/ Compliance or E = ΔPtm/ ΔV

Question 9

What is transmural pressure?

Answer 9

Transmural pressure is the difference in pressure between two sides of a wall or equivalent separator. Medically transmural pressure = blood pressure.

transmural pressure = P inside BV - P outside BV

Question 10

1) Describe the volume-pressure curves for arteries and veins.
2) Are veins or arteries more compliant?

Answer 10

1) See figure on pg.8

2) Veins! The function of veins is to hold a lot of blood volume.

Question 11

If you were to hemmorage, what would happen to the curve & the slope of the curve for the arterial system where the slope is 1/compliance? Why?

Answer 11

If I were to hemorrhage, my SNS would shift the arterial curve to the left but it does not change the slope, that is, it does not change compliance.

It does this so that at a particular volume, you are still able to keep a reasonable blood pressure to perfuse your organs even while hypotensive due to hemmorage.

See pgs 10 & 17

Question 12

When the mitral valve ____, the left ventricle is full & we are in _____. When the pressure increases, but the blood does not go anywhere, an ________ contraction occurred. Pulse pressure or SP - DP is proportional to ______ volume & inversely proportional to ______.

Answer 12

When the mitral valve closes, the left ventricle is full & we are in systole.

Isovolumetric

proportional to SV & inversely proportional to compliance
PP=SV/C

See pg. 14

Question 13

Pulse pressure ______ with increasing age since compliance_________.

Answer 13

Increases since compliance decreases–PP=SV/C

Question 14

Vessels are elastic tubes, not rigid tubes. Thus, increased internal pressure ________ the radius which in turn ________ the resistance.

Answer 14

Vessels are elastic tubes, not rigid tubes. Thus, increased internal pressure increases the radius which in turn decreases the resistance.

Question 15

Critical closing pressure (CCP) is the amount of pressure needed to keep a BV _____. So during a hemmorage CCP increases and shifts the Flow v CCP curve due to increased _______ stimulation to keep the BV’s as ______ as long as possible, to prevent blood loss.

Answer 15

open

sympathetic

closed (see pg. 17)

Question 16

Raynaud’s syndrome

Answer 16

Raynaud syndrome is excessively reduced blood flow in response to cold wheather or emotional stress, causing discoloration of the fingers, toes, and occasionally other areas.

The arteries vasoconstrict, spasm, & close, which stops perfustion. When you have an attack, the cirtical closing pressure increases (shift in curve) & keeps the arteries closed which decreases perfusion. See pg. 18.