Lecture 9-10 - Intro to CV System

Question 1

What is normal resting heart rate?

Answer 1

70 beats/min (range: 60-100)

Question 2

What is normal Cardiac Output?

Answer 2

5 L/min (CO = flow rate from 1 ventricle)

CI = is just CO adjusted for body surface area (e.g. for baby vs. adult)

Question 3

What is Stroke Volume?

Answer 3

volume ejected by 1 ventricle in 1 beat (for 170 lb person = 70 mL)

Question 4

What determines cardiac output?

Answer 4

Stroke Volume and Heart Rate:

CO = SV x HR
vol/min = vol/beat x beats/min

Question 5

What are the parameters for CV function?

Answer 5

PRESSURE:

a. Arterial Blood Pressure = systolic pressure/diastolic pressure
b. Mean Arterial Blood Pressure (MAP) = diastolic pressure + 1/3rd pulse pressure

FLOW (Q): Q = (P1-P2)/R

RESISTANCE - Impedance to blood flow in mmHg/mL/min

Question 6

How do valves contribute to pumping of blood through the body

Answer 6

through valves opening passively in response to pressure changes to allow for filling and ejecting of blood from the heart

Question 7

What is the cardiac conduction pathway?

Answer 7

SA node (normal pacemaker) to internodal pathways–> depolarization spreads to AV node (where it PAUSES allows FILLING of VENTRICLE) –>Bundle of His/AV bundle –> Purkinje fibers–> ventricular myocardium/muscle

Remember electrical events (DEPOLARIZATION) come before any kind of mechanical (CONTRACTION) event!

Question 8

Does the body’s circulation behave like a SERIES circuit?

If so, why is it important?

Answer 8

Yes! Bec/ this allows for no mixing of oxy and deoxy blood.

*realize that even though overall circulation functions as a series circuit, regional circulation circuits function in parallel

Question 9

What are low pressure, low resistance vs. high pressure circulation systems, low pressure?

Answer 9

Low pressure, low resistance: Pulmonary circuit

High pressure: Systemic circuit

Question 10

What are the distributing, exchange and collecting vessels?

Answer 10

distributing vessels: arteries
exchange vessels:capillaries
collecting (capacitance) vessels: veins

Question 11

Is CO the same for both ventricles?

Answer 11

Yes!

Volume of blood is same for both ventricles

Question 12

Flow (as a % of CO) is highest for what organ?

Answer 12

Lungs!

Question 13

What is most important for adjusting CO?

Answer 13

Venous reservoir!

Question 14

Systemic vascular resistance (total peripheral resistance) is highest in what type of blood vessels?

Answer 14

small arteries and arterioles (changes in vascular tone adjusts flow!)

Question 15

CO = ____________ return?

Answer 15

CO = Venous Return

Question 16

What does flow to a region depend on?

Answer 16

Regional resistance and Cardiac output

Question 17

Which blood vessels have the largest cross sectional area and the lowest velocity?

Answer 17

Capillaries = largest cross sectional area, lowest velocity

Question 18

What are the elements of resistance that affect flow? (according to Poiseuille’s law)

Answer 18

pressure gradient
vessel radius
fluid viscosity
tube length

Question 19

What is the formula for total peripheral resistance (systemic vascular resistance)?

Answer 19

TPR = (Aortic P - CVP)/CO

Question 20

What is he formula for pulmonary vascular resistance?

Answer 20

Pulmonary vascular Resistance = (PAP-LAP)/CO

Question 21

Is pulmonary artery resistance less than 1/10th of systemic vascular resistance?

Answer 21

Yes!

Question 22

Where is the largest pulse pressure and what is it?

Answer 22

in LV = 120/9

Question 23

What happens to mean pressure as blood flows from the aorta to arteries, capillaries, veins to RA?

Answer 23

It falls

same pattern of falling pressure also occurs in pulmonary circulation!

Question 24

Catheters can be used to directly measure what?

Answer 24

arterial pressure and venous pressure

can also measure CO via indicator dilution or thermal dilution technique

Swan-Ganz Catheter (introduced in vein) = pulmonary artery catheter uses a balloon to help it get downstream

Question 25

Filling pressure for the left atrium is also known as what?

Answer 25

Pulmonary capillary wedge pressure

Question 26

How do you measure CO?

Answer 26

indicator dilution (Indicator injected/Mean dye conc x duration of 1st circulation) where Mean dye conc = temp deflection

or thermal dilution techniques

Question 27

How does the Fick principle contribute to measure CO?

Answer 27

calculate BLOOD FLOW of an ORGAN based on uptake or removal rate of marker substance, arterial and venous concentrations of that substance across an organ. Basically, CO can be calculated via O2 consumption, arterial and venous oxygen concentration.

Question 28

Can you express resistance as a function of flow and change in pressure?

Answer 28

R = (P1 - P2)/Q for resistors in SERIES!

If resistors are in parallel: Flow = Qtot = Q1 + Q2 + Q3 so P1-P2/Rtot = 1/Rtot = 1/R1 + 1/R2 + 1/R3

Question 29

What’s the difference between laminar vs. turbulent flow?

Answer 29

laminar:
stationary flow near the walls
fluid moves in streamlines parallel to axis of tube
layers don't mix
highest velocity in the center

turbulent:
reduced flow
disorganized flow
mixing of layers
can lead to vascular disease

Question 30

What things cause turbulence?

Answer 30

high velocity flow in tube with uniform caliber
local obstruction
abrupt increase in caliber
local obstruction + increased caliber

Question 31

What’s the formula for wall tension?

Answer 31

Wall Tension = transmural pressure (Pressure inside vs. outside) x radius

T = Pr

Tendency for longitudinal slit in vessel to be pulled apart

Small radius in MICROCIRCULATION PROTECTS SMALLER VESSELS

Question 32

Do smaller vessels (microcirculation = arterioles, metaarterioles, capillaries, venules) have low wall tension and high pressure?

Answer 32

Yes! Small radius so low wall tension and high pressure

Question 33

Can Vascular disease lead to aneuyrism (increased radius) and rupture due to higher wall tension?

Answer 33

Yes!

Question 34

Pouiselle’s law relates to Resistance. You can use it, e.g., in parallel circuits. What is the formula?

Answer 34

R = (Viscosity x L x 8)/(Pi x r^4)

The greater the viscosity and length of tube and the smaller the radius, the greater the resistance and lower the flow rate.