Physiology of Circulation

Question 1

Arteries are under high or low pressure?
How strong are the walls?
Rapid or slow blood flow?

Answer 1

High pressure, strong vascular walls, rapid flow

Question 2

Arterioles are what size?
What do they act as?
What is a defining characteristic of arterioles, and what are they innervated by?

Answer 2

Final small branches of arterial system.

Act as control conduits for blood release into capillaries.

Strong muscular walls that vasoconstrict/dilate.

Innervation by SNS only

Question 3

Capillaries are what?

Defining characteristic?

How thin are the walls?

Permeable to what size substances?

Answer 3

Exchange site for nutrients, waste, electrolytes, fluid.

Very thin walls, (unicellular layer of endothelial cells)

Contain small capillary pores

Permeable to small molecular substances

Question 4

Sickle cells have what 2 characteristics that are problematic?

Answer 4

Hold less hemoglobin for O2 binding, and also due to their abnormal shape can block blood cell flow in arteries.

Question 5

Venules purpose is to what?

Answer 5

Collect blood from capillaries that merge into larger veins

Question 6

Veins major function is to what?

Low pressure or high pressure?

Thin or thick walls?

can constrict or dilate?

Answer 6

Transport blood to heart.

Major function: serve as a blood reservoir! (64% of total blood volume)

Low pressure.

Thin walls.

Constricts/Dilates. Has muscle.

Question 7

Define blood flow

Answer 7

Volume of blood flowing through vessel,organ or entire circulation in a given period.

Question 8

Blood Pressure definition

Answer 8

Force per unit area exerted on a vessel wall by the contained blood mmhg.

Question 9

Resistance definition

Answer 9

Opposes flow. Amount of friction that blood meets when passing through a vessel.

Question 10

2 factors that affect blood flow

Answer 10

Pressure and resistance

Question 11

Ohm’s Law calculates what?

Answer 11

Flow through a vessel as a function of pressure between both ends of a vessel and resistance.

F= change in pressure/resistance

Question 12

Normal adult blood flow in liters

Answer 12

5 L

Question 13

What are 2 descriptions of blood flow?

Answer 13

Laminar and Turbulent

Question 14

Define conductance

Answer 14

Measure of blood flow through a vessel for a given pressure difference.

Reciprocal of resistance.

Small changes in diameter of a vessel impact large changes in conductance.

Question 15

Poiseuille’s Law is related to what type of flow?

Answer 15

Laminar flow; by diameter.

Question 16

How much of systemic circulation is due to arteriole resistance?

Answer 16

2/3

Question 17

Viscosity has what kind of relationship to blood flow?

Answer 17

Inverse. Thickness of blood.

Question 18

Hematocrit is what?

Answer 18

% of blood that is of red blood cells.

Average male has more hematocrit than women.

Question 19

Polycythemia?

Answer 19

Higher amount of RBC than normal.

Question 20

What controls blood flow primarily?

Answer 20

Needs of the tissue!

Cardiac output controlled by sum of local tissues.

Question 21

What controls blood flow secondarily?

Answer 21

Small tissue specific vessels can dilate or constrict flow.

Question 22

Mean arterial pressure definition

Answer 22

Average blood pressure in an individual

Question 23

Pulse Pressure definition?

How does arteriosclerosis affect PP?

Answer 23

Difference between systolic and diastolic pressure.

PP will increase

Question 24

What happens to mean arterial pressure and pulse pressure as distance from heart increases?

Answer 24

They decrease.

Question 25

What is the average pressure at the venae cavae?

Answer 25

~0 mmhg

Pressure decreases steadily from capillaries–>venules –> veins –> venae cavae

Question 26

What is venous distension?

Higher in veins, or arteries?

Answer 26

Swelling or increase in volume of blood in a vessel. Sign of high blood pressure, or obstruction.

Higher in veins!

Question 27

What is vessel compliance?

Answer 27

Total quantity of blood stored in a given portion of the circulation of a vessel per unit of pressure rise.

Compliance = distensibility x volume

Question 28

Right atrial pressure is what amount?

Answer 28

0 mmhg

Question 29

What aids in venous return throughout the body?

Answer 29

Muscle pump will close one of the valves, while opening a venous valve to pump the blood towards the heart against gravity.

Question 30

Name 4 blood reservoirs (that aren’t the veins)

Answer 30

Spleen, Liver, Heart, Lungs

Question 31

What defines the acute phase of blood control?

Answer 31

Fast adjustments of arterioles and precapillary sphincters and other small vessels. (vasodilation/constriction)

Question 32

What defines long term phase of local blood control?

Answer 32

Adjustment over days/weeks/months to control blood flow to tissues.

Question 33

What are 3 theories of blood flow regulation?

Answer 33

• Vasodilator theory released from local tissues.
• Oxygen Lack theory
• Lack of other substances may also facilitate diffusion.

Question 34

Large arteries upstream respond to downstream regulation by what?

Answer 34

Release of EDRF of nitric oxide (endothelium derived relaxing factor)

Question 35

Reactive hyperemia vs Active hyperemia

Answer 35

Reactive: increase in blood flow following ischemia.

Active: increase in blood flow due to exercise or other metabolic activity.

Question 36

Deficiency of nutrients and oxygen lead to increases of what?

Answer 36

Angiogenic factors –> leading to vascularization based on need