15. DSA Circulation and Hemodynamics

Question 1

What contains a stressed volume of blood?

Answer 1

Arteries

Question 2

What is the site of the highest resistance and largest drops in pressure. Will also have Alpha1 adrenergic receptors which contract smooth muscle and increase resistance to flow?

Answer 2

Arterioles

Question 3

Which vessels contain unstressed volume of blood and have the largest percent of blood at any given time? Innervated by sympathetic alpha1 adrenergic

Answer 3

Veins and venules

Question 4

What is the equation for velocity of blood flow (v)?

Answer 4

v (velocity in cm/s) = Q (flow mL/s (volume almost) ) / A (cross sectional area cm2)

Question 5

While velocity is low in capillaries, velocity is greater near?

Answer 5

The ends (aorta, SVC/IVC)

Question 6

Blood flow (Q) is determined by?

Answer 6

Q= Change in Pressure (P) / R (resistance)

Question 7

The resistance to blood flow equation is R= 8nL/pi r^4

What does this mean?

Answer 7

A small decrease in radius will increase resistance by 16 fold
Increase in R will decrease blood flow

Question 8

Laminar flow means streamlined. Turbulent flow occurs when laminar flow is disrupted and takes more energy to drive turbulent flow forward. So laminar flow is?

Answer 8

more efficient

Turbulent flow can be heard!

Question 9

Reynolds number is used to predict whether flow will be turbulent or laminar, where less than 2000 predicts laminar flow. How is the Nr (reynolds number) calculated?

Answer 9

Nr= (p d v) / n
p density of blood
d is diameter of BV
v is velocity of blood flow
n is blood viscosity

Question 10

Shear occurs because velocity is not the same along the vessel wall as it is in the center. Where is shear great and lowest at?

Answer 10

greatest along the vessel wall and lowest in the center

Question 11

Compliance is the amount of stretchability in veins and arteries and is inverse of elasticity or recoil. Vein compliance is ______ compared to artery. What happens if the compliance decreases in a vein?

Answer 11

Vein compliance is greater than arteries

If compliance in vein decreases, the blood will be redistributed from unstressed volume to the stressed volume

Question 12

How is the pulse pressure calculated? What does it represent

Answer 12

Systolic blood pressure (SBP) minus the diastolic blood pressure (DBP)
Represents volume of blood ejected from left ventricle in a single beat

Question 13

Mean arterial pressure (MAP) is determined by?

Answer 13

MAP= 2/3 DBP + 1/3 SBP

Question 14

Microcirculation refers to capillaries and capillary beds which branch from?

Answer 14

metaarterioles

Question 15

What exchange of substances occur across the capillary wall?

Answer 15

Simple diffusion
Lipid and water soluble things
Proteins do not cross

Question 16

What are the starling forces that influence fluid exchange across the capillaries?

Answer 16

Hydrostatic tissue
Hydrostatice capillary
Oncotic capillary only force to bring fluid out from alveoli to cap
Oncotic tissue

Question 17

An Increase in filtration by the lympathic capillaries around the capillaries can be caused by what? (2)

Answer 17

1. decrease in oncotic capillary pressure from reduced plasma protein concentration
2. Increase in hydrostatic capillary pressure from increased VENOUS/arterial pressure

Question 18

What is one mechanism for control over regional flow by the maintenance of a constant blood flow in face of changing arterial pressure. This takes place in kidneys, brain, and heart

Answer 18

autoregulation

Question 19

What is a mechanism of control over regional flow in which blood flow to an organ is proportional to its metabolic activity?

Answer 19

Activer hyperemia

Question 20

What is a mechanism of control over regional flow in which increase in blood flow in response to a period of decreased blood flow?

Answer 20

Reactive hyperemia

Question 21

What does the myogenic hypothesis state?

Answer 21

If there is a stretch in the wall of arteries, the smooth muscle will constrict to increase resistanceand maintain flow

Shear stress will also contribute similar to stretch, in that greater shear stress will be synonymous with greater pressure

Question 22

Active hyperemia uses a process in which oxygen delivery is matched to oxygen consumption. What hypothesis is this know as?

Answer 22

Metabolic hypothesis

Question 23

What are some vasoactive substances along with the sympathetic NS for neuronal and hormonal control of the circulation?

Answer 23

Histamine
Bradykinin
Serotonin
Prostaglandins
Angiotensin II
Vasopressin
ANP

Question 24

What does histamine result in?

Answer 24

Dilation of arterioles and contriction of venules = increased hydrostatice pressure = edema

Question 25

In coronary, cerebral, pulmonary, and renal circulation- local metabolic control is most important while…?

Answer 25

sympathetic control is least important

Question 26

In skin and skeletal muscle (at rest) circulation, local metabolic control is least important while?

Answer 26

sympathetic control is most important using Alpha 1 adrenergic receptors for vasoconstriction and B2 for vasodialation