Exam II: 3B Hempdynamics

Question 0

When the blood leaves the L. atrium–> L. ventricle–>Aorta where does most the blood go to?

Answer 0

1) Renal 25%
2) GI 25%
3) Skeletal muscle 25%

Question 1

What is Hemodynamics?

Answer 1

Refers to the principles that govern BLOOD FLOW in the cardiovascular system

Question 2

What are the 2 variables that blood flow is affected by?

Answer 2

Blood flow thru arteries is affected by pressure and resistance

Question 3

What is the formula for Ohm’s Law?

Answer 3

Q= Delta P/R

Question 4

What is Blood Flow (Q)?

Answer 4

Quantity of blood flowing through a vessel, organ, or the entire circulation in a given period of time (L/min)

Question 5

What is blood flow drive by?

Answer 5

By the pressure differences (gradients) in the same sense that simple diffusion of chemical substances is driven by concentration difference or gradients.

Question 6

What is Blood Pressure?

Answer 6

The force with which blood is pushed against the walls of blood vessels.

Question 7

What is Systolic Pressure (SP) ?

Answer 7

Highest amount of pressure reached during ventricular ejection of blood

Question 8

What is Diastolic Pressure (DP)

Answer 8

Minimum amount of pressure just before ventricular ejection begins

Question 9

What is the physics of SP and DP?

Answer 9

Part of the energy of ventricular contraction provides flow during ventricular systole. The remainder is used in distending the arterial tree & stored as potential energy.
-This potential energy is released by the RECOIL of the arterial wall, provides a more continuous (Rather than pulsatile) flow to the peripheral tissues. This pressure- storing property of the aorta is called the “Wind Kessel” effect

Question 10

What is the Auscultatroic measurement?

Answer 10

Determines blood pressure by monitoring KOROTKOFF SOUNDS. A cuff placed around upper arm, vertical height as heart, normally by squeezing a rubber bulb until artery is completely occluded (30 mmHg above systolic pressure) Then the pressure cuff is released. When blood starts flowing, the flow crates a pulse synchronic pounding (1st KOROTKOFF SOUND).
Pressure detected @ systolic blood pressure. Cuff pressure released until no more sound can be detected @ the diastolic arterial pressure

Question 11

What is Oscillometric measurement?

Answer 11

Devices use an electronic pressure sensor w/ a numerical readout of blood pressure. In most cases the cuff is inflated & released by electrically operated pump & valve. Initially pressure is in excess of the systolic pressure and then pressure reduces to below diastolic pressure. Once blood is there, but restricted, the cuff pressure will vary periodically in synchrony with cyclic expansion & contraction of the brachial artery.
The values of systolic and diastolic pressure are computed using algorithm.

Question 12

What is the Mean Arterial Pressure (MAP) ?

Answer 12

The actual pressure that propels blood to tissues; The “average” pressure in a cardiac cycle

MAP= 2/3 DP + 1/3 SP
or
MAP=DP + 1/3 PP

Question 13

What is resistance?

Answer 13

The opposition to blood flow

Question 14

What is the Total Peripheral Resistance(TPR) or Systemic Vascular Resistance (SVR)?

Answer 14

The sum of all resistance in the vasculature

Question 15

What are the 3 important sources of resistance within a single vessel?

Answer 15

1) Blood viscosity
2) vessel length
3) vessel diameter or radius

Question 16

Which of of these 3 resistance sources DOES NOT change appreciably in vivo?

Answer 16

VESSEL LENGTH

Question 17

What is Poiseuille’s Law?

Answer 17

The relationship between resistance, viscosity, vessel length, and vessels radius is explained with Poiseuille’s Law

R= 8 V L/ Pi r^4

Question 18

What is the Hematocrit formula equal to

Answer 18

Hematocrit (%) = Red cells/Blood x 100

Question 19

What is blood viscosity depend on?

Answer 19

Several factors, concentration of the suspended medium (formed elements)

Question 20

What is another factor that influences viscosity is ?

Answer 20

Tendency of RBCs to aggregate into stack or “ROULEAUX” at lower flow velocities.

Question 21

When is blood viscosity exaggerated causing pronounced cell clumping or “sludge” in the microcirulation w/ severe hindrance to flow & resultant tissue ischemia ??

Answer 21

In burns or shock

Question 22

What is the blood vessel radius relationship?

Answer 22

Resistance is inversely proportional to the 4th power of the vessel radius.

A 2-fold increase in vessel radius increases flow by 16 fold
A 4-fold increase in vessel radius increases flow by 256 fold

Question 23

Do drugs that dilate the vessel therefore have a powerful effect on blood flow?

Answer 23

yes

Question 24

Trace the path of arteries with relation to resistance, pressure and blood flow.

Answer 24

Vasoconstriction–>Resistance increases more than pressure–>blood flow DECREASES

Question 25

Trace the path of veins with relation to resistance, pressure and blood flow.

Answer 25

Venoconstriction–>Pressure increases more than resistance–>Blood flow INCREASES–>Venous return increases