Physiology of Circulation

Question 1

Circulation is primarily influenced by what?

Answer 1

tissue needs

Question 2

3 characteristics of arteries?

Answer 2

1) transport blood under high pressure
2) strong vascular walls
3) rapid blood flow

Question 3

4 characteristics of arterioles?

Answer 3

1) final small branches of arterial system
2) act as control conduits - blood released into capillaries
3) strong muscular walls that vasoconstrict/dilate
4) innervated by SNS only

Question 4

4 characteristics of capillaries?

Answer 4

1) exchange site for nutrients, wastes, electrolytes, fluid
2) very thin walls
3) contain small capillary pores
4) permeable to small molecular substances, H2O

Question 5

3 characteristics of venules?

Answer 5

1) gathers low oxygenated blood
2) collects blood from capillaries
3) gradually merge into larger veins

Question 6

Major function of veins?

Answer 6

• serve as a blood reservoir (64% of total blood volume)

- transport blood from tissues to heart

Question 7

Distribution of blood volume?

Answer 7

• veins = 64%
• arteries = 15%
• capillaries = 5%
• pulmonary = 9%
• heart = 7%

Question 8

What is the volume of blood flowing through a vessel, an organ, or the entire, circulation in a given period (ml/min)?

Answer 8

blood flow

Question 9

What is the force per unit area exerted on a vessel wall by the contained blood (mmHg)?

Answer 9

blood pressure

Question 10

What is the opposition to flow; amount of friction blood meets when passes through the vessels?

Answer 10

resistance

Question 11

Blood flow is affected by what 2 factors?

Answer 11

• pressure gradient

- vascular resistance

Question 12

What is the calculation of flow through a vessel?

Answer 12

Ohm’s law:

blood flow = change in pressure between 2 ends of vessel/ resistance

Question 13

What is the normal adult overall blood flow?

Answer 13

5,000 ml/min = cardiac output

Question 14

What are the two descriptions of blood flow?

Answer 14

• laminar

- turbulent

Question 15

What is known as the measure of blood flow through a vessel for a given pressure difference? Also known as the reciprocal of resistance?

Answer 15

conductance

Question 16

What plays the greatest role in determining rate of blood flow?

Answer 16

diameter

Question 17

What controls most of the blood flow through the vessels?

Answer 17

arterioles

Question 18

An increase in viscosity does what to blood flow?

Answer 18

decreases blood flow

- inverse relationship

Question 19

What is known as the percent of blood that consists of cells (RBC and WBC)?

Answer 19

% of blood that consists of cells

Question 20

What tightly controls blood flow?

Answer 20

needs of tissue

Question 21

What is controlled independently of local blood flow or cardiac output?

Answer 21

arterial pressure

Question 22

What is known as the pressure that propels blood to tissues?

Answer 22

mean arterial pressure (MAP)

Question 23

equation for MAP?

Answer 23

MAP = DBP + (pulse pressure/3)

Question 24

What is pulse pressure?

Answer 24

difference between systolic and diastolic pressure

Question 25

MAP and pulse pressure decrease with and increase in what?

Answer 25

increasing distance from the heart

Question 26

2 effects of pressure on blood flow?

Answer 26

• increases force on blood flowing through vessels

- distends vessel (expands or stretches the vessel which increases blood flow)

Question 27

Veins have a _______ distensibility than arteries?

Answer 27

greater

Question 28

What is known as the total quantity of blood that can be stored in a given portion of the circulation for each mmHG pressure rise?

Answer 28

compliance (capacitance)

Question 29

equation for compliance?

Answer 29

distensibility x volume

Question 30

What is another name for right atrial pressure?

Answer 30

central venous pressure

Question 31

What are the 5 blood reservoirs of the body?

Answer 31

• veins
• spleen
• liver
• heart
• lungs

Question 32

Do different tissues have different metabolic needs over time?

Answer 32

YES (blood flow/100g of tissue)

Question 33

What are the 2 phases of local blood control?

Answer 33

• acute

- long term

Question 34

What is the effect on blood flow with decreased oxygen?

Answer 34

increased blood flow

Question 35

What is stated by the vasodilator theory?

Answer 35

• vasodilator substance released from local tissue when there is low oxygen in that particular area
• causes more blood flow to that local tissue area

Question 36

What is stated by the Oxygen Lack Theory?

Answer 36

• the precapillary and metarteriole sphincters constrict the vessels
• but once you start moving, oxygen reduces and now the sphincters open and allow for dilation to increase blood flow

Question 37

What are the effects of nitric oxide?

Answer 37

vasodilator that allows for more blood flow which allows for more nutrients to get to the tissues

Question 38

2 other methods affecting local blood flow?

Answer 38

• reactive hyperemia

- active hyperemia

Question 39

Do tissues have the ability to autoregulate?

Answer 39

YES – after increase in BF to a tissue due to increase in arterial pressure, BF returns to near normal levels

Question 40

4 vasoconstrictors?

2 vasodilators?

Answer 40

Vasoconstrictors:
- norepinephrine/epinephrine
- angiotensin II
- vasopressin
- endothelin
Vasodilators:
- bradykinin
- histamine