Blood Flow Pressure/Resistance

Question 1

What major factors affect Blood flow and pressure?

Answer 1

• Cardiac Output
• Compliance
• Volume
• Resistance
• Vessel Length
• Vessel Diameter

Question 2

Define Perfusion.

Answer 2

∆P along a vessel access.
Pressure difference upstream to
downstream. Pressure loss.

Question 3

Compare Laminar and Turbulent flow?

Answer 3

Laminar Flow: Fluid elements in any given lamina remain in that lamina as fluid moves longitudinally along the tube.

Turbulent: Fluid elements in any given lamina remain in that lamina as fluid moves longitudinally along the tube.

Question 4

What is Reynolds numb Er, and how is it calculated?

Answer 4

• Ratio of inertial to viscous forces for a fluid flowing through a cylinder
• Determines laminar vs Turbulent flow
• N = pDv/n
• > 3000 turbulent
• <2000 laminar

Question 5

Murmur

Answer 5

when turbulence occurs in the heart

Question 6

Bruit

Answer 6

when turbulence occurs in the vessel.

Question 7

What is Shear Stress?

Answer 7

As blood flows through a vessel, it exerts a force on the vessel wall
parallel to the wall.

Question 8

What is the Two plates model of Viscosity?

Answer 8

provides there are two
plates with fluid in-between.
• Two criteria: 1. fluid does not glide along but is in contact. An
adhesive force operates between fluid + plates. 2. flow is laminar. Thin layers + no turbulence
• Lower plate does not move + upper plate drifts aside

Question 9

How are Velocity and Flow of a fluid related in a rigid tube?

Answer 9

V = Q/A (A = SA)

Question 10

What is the determining factor for how erythrocytes flow in vessels?

Answer 10

• Flexibility of RBCs
• At low flow rates like in microcirculation rigid particles do not migrate toward the central axis of a tube and flexible
  particles do.

Question 11

How are viscosity and shear rate related?

Answer 11

apparent viscosity of blood diminishes as the

shear rate is increased

Question 12

How does Fibrinogen affect flow?

Answer 12

• Large plasma protein

- High fibrinogen causes aggregation —> more viscous blood —> change in flow

Question 13

What law is used to determine flow of a fluid through cylindrical tube?

Answer 13

• Poiseulle’s law

- Q = piPr^4 / 8nl

Question 14

What are the two categories of superficial stress to blood vessels?

Answer 14

Circumferential: due to pulse pressure variation inside the vessel. Intravascular hydrostatic pressure produces not only
circumferential but also normal tensions

Shear Stress: Due to blood flow

Question 15

What are major vasodilators and vasoconstrictors?

Answer 15

Vasodilators:

• Low O2, High CO2, INC metabolic acids, High NO, High L, High H+
• Inflammation
• INC blood flow
• relaxed precapilary sphincters

Vasoconstrictors:

• Prostaglandins; Activated platelets; Leukocytes, endothelium
• Cinricted precapilary sphincters
• DEC blood flow

Question 16

What are the endocrine regulators of Blood pressure?

Answer 16

Renal: Erythropoeitin; RAS
Adrenal: Catecholamines
Brain: Antidiuretics
Heart: ANP

Question 17

How is blood pressure estimated?

Answer 17

CO x TPR

Question 18

What is the action of Spironolactone?

Answer 18

Blocks Aldosterone receptors in kidney

Question 19

What is the main function of Alpha 1 receptors?

Answer 19

Smooth muscle contraction

Question 20

What is the main function of Alpha 2 receptors?

Answer 20

Inhibits secretory activity

Question 21

What is the main function of Beta 1 receptors?

Answer 21

Increases HR, Conduction, and contractility

Question 22

What is the main function of Beta 2 receptors?

Answer 22

Inhibits smooth muscle contraction, stimulates GNG, Glycgenolysis, lipolysis, secretion of glucagon, and RAAS

Question 23

What are the two controls for arterial blood pressure?

Answer 23

Neural: Baroreceptor reflex

Hormonal: RAAS

Question 24

What are the two primary effects of Angiotensin II?

Answer 24

• Stimulates Adrenal cortex to synthesize and secrete Aldosterone
• Causes Vasoconstriction of arterioles