Mutafova Arteries & Veins

Question 1

What are the 3 main functions of arteries?

Answer 1

conduit, hydraulic filters, storage of blood

Question 2

What are the 3 main functions of veins?

Answer 2

conduits, major reservoir of blood, regulator of cardiac output

Question 3

What does it mean for an artery to be a conduit?

Answer 3

They move blood from the heart to circulation.

Question 4

What does it mean for an artery to be a hydraulic filter?

Answer 4

Prevent pulsatile pressure from large arteries from going into the capillaries b/c of the elastic fibers etc that make up arteries.

Question 5

How do arteries act as a storage of blood?

Answer 5

During systole, the arteries are distensible. Can store some blood.

Question 6

What is the relationship b/w the distensibility of the arteries & the cardiac cycle?

Answer 6

During systole…blood goes to the capillaries & the arteries are distensible, storing some blood.
During diastole…blood continues to go to the capillaries b/c the arteries recoil.

Question 7

How is it possible that the veins regulate cardiac output?

Answer 7

Because venous return affects cardiac output & the veins are a huge reservoir of blood.

Question 8

What tissues are found in the tunic media of blood vessels? What about the tunic adventitia?

Answer 8

media: smooth muscle, collagen, elastin
adventitia: collagen, fibroblasts, vasa vasorum, nerves

Question 9

Where is the autonomic nervous control found in terms of the layers of the blood vessels?

Answer 9

Tunica Adventitia. The place for innervation of the blood vessels. Gap jcns relay this message thru the smooth muscle cells.
NT diffuses thru gap jcns of smooth muscle cells to get to the endothelial cells for the NO mechanism.

Question 10

Veins have a larger cross sectional area than arteries…what does this mean for velocity?

Answer 10

Larger Cross sectional area means lower velocity…this sorta relates to the storage of blood in veins.

Question 11

What are the approx pressure in large veins? And in the RA?

Answer 11

RA 0 mmHg

Large Veins 4-7 mmHg

Question 12

Where does the resistance in the veins come from?

Answer 12

Not from the blood vessel itself (large diameter in large veins).
Resistance for veins comes from compression by the surrounding tissues.

Question 13

What is compliance?

Answer 13

The same as capacitance.
The amount of blood that can be stored in a given portion of veins/arteries given a certain rise in pressure.
C=dV/dP
Compliance=Increase in Volume that it can hold/Increase in pressure

Question 14

Which is distensible, compliant, capacitant?

Arteries, veins?

Answer 14

Arteries have high distensibility (not as high as veins). Low capacitance & compliance. (same thing)
Veins have highest distensibility & high capacitance= compliance.

Question 15

What is distensibility?

Answer 15

NOT the same as compliance.
Compliance=Distensibility X Volume (initial)
D=C/V
So like arteries are distensible b/c that is what allows them to handle the pulsatile flow.
Veins are the most distensible, tho, which is why an increase in pressure, causes a significant increase in storage of blood.

Question 16

What is the idea of delayed compliance? How does this concept relate to a large transfusion or hemorrhage?

Answer 16

If you inject a ton of extra blood…the pressure on the venous wall will increase. Then b/c of their compliance they will increase their diameter & the pressure on their venous walls will decrease. This is delayed compliance.
If you lose a ton of blood…the pressure on the venous wall will greatly decrease immediately. Then b/c of their compliance they will decrease their diameter & the pressure on their venous walls will increase. This is also the concept of delayed compliance.

Question 17

Why is the distensibility of the veins so important for consistent capillary blood flow?

Answer 17

With arteries will normal distensibility…
During systole there is blood flow to the capillaries AND there is storage of blood (b/c of dilation of the aorta) in the large arteries.
During diastole the arteries recoil & this blood flows to the capillaries.
Clearly this flow is consistent.
With arthersclerosis or rigidity of blood vessels w/ age…this recoil & initial distensibility are not present. Therefore, capillaries only receive blood flow during systole, not during diastole. This blood flow to capillaries is discontinuous.

Question 18

When you age…what happens to your aorta?

How does this relate to pulsatile flow?

Answer 18

Your aorta becomes more rigid.
It is less compliant. Less distensible.
The diameter of your aorta changes less in response to the pulsatile flow as you age.

Question 19

Is the innervation of blood vessels provided by the parasympathetic system or the sympathetic system?

Answer 19

Sympathetic system.

Question 20

Review: what is tyrosine hydroxylase?

Answer 20

It is the enzyme used in nerve terminals for the synthesis of NT…particularly NE. It is found in the tunic adventitia of blood vessels b/c this is where the neural innervation is.

Question 21

What part of the vasculature is innervated by the sympathetic system?

Answer 21

ALL of it except for the capillaries.

Question 22

Which vessels are more responsive to sympathetic nerve stimulation–arteries or veins?

Answer 22

Veins. Surprisingly.
They have more innervation, more NT released, more of a contractile response.
Overall: they are more responsive in times of hyperactivity of the symp system like hemorrhage, exercise etc.
This is super duper important b/c you need to increase venous return to increase cardiac output in these stressful times.
According to Nolan…venoconstriction: CO increases
Vasoconstriction: more about distribution of blood flow.

Question 23

What does sympathetic stimulation do to the pressure of the vasculature at each volume?

Answer 23

It increases the pressure.

Question 24

What is the central venous pool?

Answer 24

It is in b/w the venous return & cardiac output.

It is composed of the great veins in the thorax & the RA.

Question 25

What is central venous pressure?

Answer 25

It is the pressure of the filling of the RA. It is the pressure of the thoracic vena cava.
It is approximated by the pressure of the RA.
It helps determine preload which affects stroke volume.

Question 26

What would be the significance of the following Central venous pressures? 
0 mmHg
2 mmHg
4-6 mmHg
-3- -5 mmHg

Answer 26

0 mmHg: normal.
2 mmHg: still normal.
4-6 mmHg: Congestive Heart Failure…cardiac myocytes not working very well. Maybe need a huge blood transfusion. B/c of delayed compliance…higher CVP.
-3–>-5 mmHg: hemorrhage…a huge loss of blood and a neg. CVP b/c of delayed compliance.

Question 27

What is a normal chest cavity pressure or intrapleural pressure?

Answer 27

-3 –> -5 mmHg

Question 28

What is a normal abdominal cavity pressure or peritoneal pressure?
What could raise this pressure to say 30 mmHg?

Answer 28

6 mmHg
Could be substantially raised by masses in the abdominal cavity…such as fluid buildup (ascites) or pregnancy or a tumor.

Question 29

What is a normal pressure for the peripheral small veins? What creates this pressure?

Answer 29

4-7mmHg

the compression of the surrounding tissues.

Question 30

How can you increase the central venous pressure?

Answer 30

Increasing the volume of blood in the thoracic veins.
Decrease the compliance of the veins.
It appears that venoconstriction accomplishes both of these things and increases CVP.

Question 31

If central venous pressure increases…what does that do to venous return? Why?

Answer 31

It decreases the dP b/w the peripheral venous pressure & the central venous pressure. this will cause a decrease in venous return which thrives on pressure differences.

Question 32

How do changes in the peripheral venous pressure affect the venous return?

Answer 32

Increase in the blood volume in the periphery or increase in venous tone (venoconstriction) will increase dP & will increase venous return.

Question 33

What happens if venous return is not equal to cardiac output?

Answer 33

Blood would accumulate in either the central venous pool or the peripheral venous pool.

Question 34

What is the mean systemic pressure?

Answer 34

It is the pressure in the system when the cardiac output is at zero. It is shown on the graph as the intercept on the x axis of the venous return line.

Question 35

If you just randomly increased the blood volume...what would happen to...
mean systemic pressure
venous return
RA pressure
CO

Answer 35

Blood volume increases
Mean systemic pressure increases
Venous return increases
RA pressure increases
CO increases

Question 36

What happens to the right ventricular preload when the following changes happen?
Atrial contractility decreases
ventricular compliance increases
heart rate increases
ventricular failure

Answer 36

Atrial contractility decreases–>right ventricular preload decreases
Ventricular Compliance increases–>right ventricular preload increases
Heart rate increases–>right ventricular preload decreases
Ventricular failure–>right ventricular preload increases

Question 37

If there is inflow resistance…in the sense of tricuspid valve stenosis…what happens to right ventricular preload?
If there is outflow resistance & after load increase…like pulmonic valve stenosis…what happens to the right ventricular preload?

Answer 37

Inflow resistance: right ventricular preload decreases

Outflow resistance: right ventricular preload increases.

Question 38

What can increase or decrease venous pressure? What would an increase in venous pressure do to right ventricular preload?

Answer 38

Increase Venous Pressure: increase in venous return, increase in total blood volume, respiration, muscle contraction, gravity.
Decrease Venous Pressure: increase in venous compliance.
Increase in Venous Pressure: increases right ventricular preload.

Question 39

What are some factors that affect venous return?

Answer 39

Blood volume increases, vr increases
systemic pressure increases, vr increases
venous tone increases, vr increases
skeletal muscle movement increases, vr increases
intrapleural pressure decreases, vr increases
venous valves help increase vr
low RA pressure increases vr

Question 40

What are the different factors that play a role in the venous pump?

Answer 40

One way valves
large diameter veins (larger during inspiration b/c of decreases intrapleural pressure)
propelled forward by skeletal muscle movement (like movement of the diaphragm downward w/ expiration)

Question 41

What does Toriccelli’s Law explain?

Answer 41

That at the level of the heart (akin to the surface) the pressure is equal to that of the atmosphere. But that below that the pressure rises. This explains why the pressure is so high near the feet.

Question 42

What is hydrostatic pressure & how does this relate to the venous pump?

Answer 42

The pressure in the body from the weight of the blood. This pressure is reduced in the veins w/ the help of the valves of the venous pump. After contraction, they close & break up the column of blood & lower the pressure.