DSA: Circulation and Hemodynamics

Question 1

Site of highest resistance and largest drop in pressure across

Answer 1

Arterioles

Question 2

when activated, elicits contraction of smooth muscle and vasoconstriction and increased resistance to flow

Answer 2

alpha-1 adrenergic receptors

Question 3

when stimulated elicits relaxation of smooth muscle and vasodilation

Answer 3

Beta-2 adrenergic receptors

Question 4

Site of exchange of products, a single layer of endothelial cells surrounded by basal lamina

Answer 4

capillaries

Question 5

contains unstressed volume of blood and largest % of blood at any given time

Answer 5

venules and veins

Question 6

contains stressed volume of blood

Answer 6

arteries

Question 7

What does velocity in circulation is greater at the ends mean?

Answer 7

That while velocity is low in the capillaries, it is higher in the arteries and veins especially in the vena cava

Question 8

Relationship between flow and pressure difference and resistance

Answer 8

Flow is proportional with the pressure difference and inversely proportional to the resistance

Question 9

What is the major mechanism to changing flow

Answer 9

Changing the resistance of a vessel at the arteriolar level

Question 10

When does turbulent flow occur

Answer 10

Turbulent flow occurs when laminar flow is disrupted and takes more energy to drive turbulent flow forward, while laminar flow is more efficient

Question 11

What do bruits indicate?

Answer 11

Stenosis. Bruits can be heard when turbulent flow occurs in an artery or other vascular channel.

Question 12

Laminar flow

Answer 12

Means streamlines which means that velocity is greatest at the center and the least towards vessel walls

Question 13

What predicts whether flow will be turbulent or laminar?

Answer 13

Reynolds number - influenced by changes in viscosity or velocity of blood flow

Question 14

What happens when a vessel is partially occluded

Answer 14

Blood velocity will increase at this site

Question 15

Describe shear in blood vessels

Answer 15

shear stress occurs because velocity is not the same along the vessel wall as it is in the center, it is greatest along the vessel wall and lowest at the center

Question 16

compliance of blood vessels

Answer 16

• represents distensibility of a vessel and inverse of elasticity
• compliance is greatest in veins compared to arteries

Question 17

What happens when the compliance of veins is decreased (i.e. vasoconstriction)?

Answer 17

there will be a redistribution of blood from the unstressed volume to the stressed volume

Question 18

unstressed volume

Answer 18

• volume of blood in veins

- volume of blood that produces no pressure

Question 19

stressed volume

Answer 19

• volume of blood in arteries

- volume that produces pressure by stretching the elastic fibers in the blood vessel walls

Question 20

Starling Equation

Answer 20

Jv = Kf [(Pc-Pi) – (πc – πi)]

Question 21

Changes in Starling Forces

Answer 21

increase in filtration can be caused by increases in Pc or decreases in πc

Question 22

Increases in Pc

Answer 22

Venous constriction leads to increases venous pressure, heart failure and ECF volume expansion (edema)

Question 23

Decrease πc

Answer 23

reduced plasma concentration leads to severe liver failure, protein malnutrition, loss of protein in urine

Question 24

What is active hyperemia?

Answer 24

When the blood flow to an organ is proportional to its metabolic activity

Question 25

What is reactive hyperemia?

Answer 25

An increase in blood flow in response to a period of decreased blood flow (i.e. ischemia-reperfusion)

Question 26

Myogenic response

Answer 26

increased in arterial pressure, the arterioles are stretched and vascular smooth muscle contracts in response to increasing resistance and maintain flow

Question 27

Shear stress when vascular smooth muscle is stress

Answer 27

Lead to greater pressure

Question 28

Metabolic control

Answer 28

oxygen delivery is matched to oxygen consumption

Question 29

What is the response when oxygen consumption is increases in metabolic control?

Answer 29

Vasodilatory metabolites are released to dilate vascular smooth muscle and increase blood flow

Question 30

Histamine and Bradykinin

Answer 30

released in response to trauma and causes dilation of arterioles and constriction of venules, lead to local edema

Question 31

Serotonin

Answer 31

release in response to damage, leads to vascular spasm and is a vasoconstrictor

Question 32

Prostacyclin / Pg-E

Answer 32

causes dilation

Question 33

Thromboxane A2 / Pg-F

Answer 33

causes constriction

Question 34

NO

Answer 34

vasodilator and relaxes vascular SM

Question 35

Angiotension II and vasopressin

Answer 35

constrictors that increase TPR