Circulation

Question 1

function of circulation

Answer 1

transport

• nutrients and O2 to tissues
• waste and CO2 away from tissues
• hormones from one area of body to another
• heat throughout the body

Question 2

guiding principles of circulation

Answer 2

circulation primarily influenced by tissue needs
cardiac output is a response to vascular inflow
arterial pressure generally controlled independently of local tissue flow or CO

Question 3

key factors influencing circulation

Answer 3

blood flow
pressure
resistance
control mechanisms mediating these characteristics

Question 4

characteristics of arteries

Answer 4

transport blood under high pressure

strong vascular walls

Question 5

characteristics of arterioles

Answer 5

act as control conduits
strong musclar walls that vasoconstrict/dilate
innervated by SNS only

Question 6

characteristics of capillaries

Answer 6

exchange site for nutrients, wastes

directed by local tissues, rather than SNS, to determine dilation/constriction

Question 7

characteristics of veins

Answer 7

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

contain muscle - can constrict/dilate

Question 8

function of sphincters in capillaries

Answer 8

open or close in response to need for blood

Question 9

blood flow definition

Answer 9

the volume of blood flowing through a vessel, an organ, or the entire circulation in a given period

Question 10

blood pressure definitiion

Answer 10

the force per unit area exerted on a vessel wall by the contained blood

Question 11

resistance definition

Answer 11

opposition to flow; amount of friction blood meets when passing through the vessels

Question 12

what are the 2 factors that affect blood flow?

Answer 12

pressure gradient

vascular resistance

Question 13

Ohm’s Law for blood flow

Answer 13

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

Question 14

2 descriptions of blood flow

Answer 14

laminar
-linear, parallel flow
turbulent

Question 15

conductance

• units
• what is it?

Answer 15

ml/sec/mmHg
measure of blood flow through a vessel for a given pressure difference
reciprocal of resistance
small change in vessel diameter causes enormous change in conductance

Question 16

Poiseuille’s Law

• related to what type of blood flow
• what plays the greatest role in determining rate of blood flow

Answer 16

related to laminar flow

diameter

Question 17

2/3 of resistance to flow is _____ resistance

Answer 17

arteriole

Question 18

arteriole walls can change diameter up to _____

Answer 18

fourfold

Question 19

viscosity relationship to blood flow

Answer 19

inverse

Question 20

what is hematocrit?

-typical value

Answer 20

% of blood that consists of cells

40

Question 21

how can hematocrit increase?

Answer 21

living at altitude

Question 22

theory of circulatory function

Answer 22

needs of tissue tightly controls blood flow; small tissue-specific vessels dilate or constrict locally to control flow in addition to change in cardiac output
-cardiac output primarily controlled by sum of all local tissue flows
in general, arterial pressure is controlled independently of local blood flow or cardiac output

Question 23

MAP

• what is it?
• equation

Answer 23

pressure that propels blood to tissues

DBP + 1/3 (SBP-DBP)

Question 24

mean pressure at

• venae cavae
• capillaries
• pulmonary circulation

Answer 24

vena cavae
-0 mmHg
capillaries
-17 mmHg
pulmonary circulation
-16 mmHg

Question 25

effects of pressure on blood flow

Answer 25

increases force on blood flowing through vessels
distends vessel
-increases blood flow

Question 26

do veins or arteries have more distensibility

Answer 26

veins

Question 27

compliance definition

Answer 27

capacitance

total quantity of blood than can be stored in a given portion of the circulation for each mmHg pressure rise

Question 28

compliance equation

Answer 28

distensibility x volume

Question 29

gravitational effect on venous pressure

• quiet stance
• movement - “venous pump”

Answer 29

quiet stance
-90 mmHg if you are standing still
movement
-15 mmHg

Question 30

two phases of local blood control

Answer 30

acute
-fast adjustment of arterioles, metarterioles, and precapillary sphincters
long-term
-adjustment over days/weeks/months to control blood flow to tissue

Question 31

vasodilator theory of blood flow regulation

Answer 31

vasodilator substance released from local tissue
examples
-adenosine, CO2, adenosine phosphate compounds
-histamine
-potassium ions
-H+

Question 32

oxygen lack theory (nutrient lack theory)

Answer 32

sphincters don’t have enough oxygen to remain closed
precapillary sphincters
metarteriole sphincters
other “lack of substances” may facilitate vasodilation

Question 33

dilating “upstream” arteries

Answer 33

larger arteries “upstream” from local tissue control response to effects of “downstream regulation”
drag on “upstream” endothelium of vessel walls by rapid increased flow allows release of substance that can vasodilate the “upstream” vessels
-EDRF made primarily of nitric oxide
-reduces the resistance to blood flow in upstream arteries

Question 34

reactive hyperemia

Answer 34

what happens when you restrict blood flow for a period of time

Question 35

active hyperemia

Answer 35

what you get then you exercise

actively using tissues

Question 36

autoregulation of BF

Answer 36

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