Cardio - Vascular Function

Question 1

What is the pressure and resistance of the aorta and large arteries?

Answer 1

Blood pressure is high (110mmHg) and resistance is low

-average pressure change from aorta to large arteries is relatively the same

Question 2

When does blood pressure begin to drop and why?

Answer 2

When blood reaches the small arteries is where we encounter resistance

Question 3

Where is the greatest resistance?

Answer 3

In the arterioles

-accounts for ~1/2 the total resistance in the entire systemic circulation

Question 4

What is the pressure in the arterioles?

Answer 4

55mmHg

Question 5

What is the blood pressure of blood going from arterioles to capillaries?

Answer 5

40mmHg

Question 6

What is the blood pressure within the capillaries?

Answer 6

20mmHg

Question 7

What is the blood pressure when blood goes from capillaries to venules?

Answer 7

10-15mmHg

Question 8

What is the blood pressure when blood finally reaches the right atrium?

Answer 8

Pressure is almost 0

-encounters small but significant amount of resistance

Question 9

What drives the blood through the vessels?

Answer 9

Pressure change through the system

Question 10

What causes the blood to flow through circulation?

Answer 10

Drop in pressure from high (aorta) to low (veins)

Question 11

What is blood flow effected by?

Answer 11

Pressure change (or pressure gradient) between 2 points and resistance in the circulatory system

Question 12

Simplified, what is the resistance effected by?

Answer 12

Radius of the vessel

• smaller the radius the greater the resistance
• values normally don’t change much

Question 13

What is the equation for blood flow?

Answer 13

(P1-P2) x r^4

-therefore small changes in the radius will have a large effect on blood flow

Question 14

What does flow into vessels have to equal?

Answer 14

Flow out of vessels

-division of quantities can be different but the overall output has to be the same

Question 15

What happens to the pressure gradient if one vessel radius is reduced?

Answer 15

The vessels before and after the reduced radius vessel will increase output and therefore increase the blood flow

Question 16

Which change in blood flow is better?

Answer 16

Change in radius diameter is better for us than a change in pressure

Question 17

What pressure and volume characteristics contribute to circulation?

Answer 17

structural properties

Question 18

What is blood velocity?

Answer 18

Is the speed at which the blood is moving through a particular blood vessel (cm/sec)

Question 19

What is blood flow?

Answer 19

The volume of blood moving through a set of vessels (L/min)

Question 20

What is the blood flow a rest?

Answer 20

5ml/min

-same throughout the systemic system

Question 21

Why is mean blood velocity higher in aorta then vena cava but blood flow stays the same?

Answer 21

Because the vena cava has a slightly larger diameter

• inorder to have the same blood flow, blood has to move faster through the narrow vessels (aorta)
• therefore velocity is higher in the aorta than the vena cava

Question 22

What happens when you keep dividing into more vessels?

Answer 22

The velocity decreases

Question 23

Why is velocity so low in capillaries ?

Answer 23

Since there is so many of them, the same amount of blood is spread out further to maximize diffusion
-as they start to reunite with the venues velocity starts to increase but not as high as the aorta because the diameter of the vena cava is bigger

Question 24

What are the 3 layers of arteries and veins?

Answer 24

1. Outer layer (tunica externa)- fibrous connective tissue
2. Mid layer (tunica media)- Smooth muscle and elastic tissue
3. Inner layer (tunica interna)- Endothelial cells

Question 25

What are capillaries only made up of endothelial cells?

Answer 25

To permit the diffusion of substances into and out of the blood

Question 26

What does the function of a vessel/artery depend on?

Answer 26

The content of each of the 3 tissues

Question 27

What are the blood characteristics like in the aorta and large arteries?

Answer 27

high 120mmHg and pulsatile

high blood velocity

Question 28

What is the structure like of the aorta and large arteries like?

Answer 28

Large diameters
Lots of elastic tissue
Relatively thin walls which can be easily distended = low resistance to blood flow
-average blood pressure doesn’t drop much

Question 29

What is the purpose of the aorta and large arteries?

Answer 29

“shock absorbers” when he heart ejects blood into these vessels (up to 70ml) so the arteries can absorb the amount of blood being pumped out

Distributes blood