Lecture 9-10 - Intro to CV System Flashcards
What is normal resting heart rate?
70 beats/min (range: 60-100)
What is normal Cardiac Output?
5 L/min (CO = flow rate from 1 ventricle)
CI = is just CO adjusted for body surface area (e.g. for baby vs. adult)
What is Stroke Volume?
volume ejected by 1 ventricle in 1 beat (for 170 lb person = 70 mL)
What determines cardiac output?
Stroke Volume and Heart Rate:
CO = SV x HR vol/min = vol/beat x beats/min
What are the parameters for CV function?
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
How do valves contribute to pumping of blood through the body
through valves opening passively in response to pressure changes to allow for filling and ejecting of blood from the heart
What is the cardiac conduction pathway?
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!
Does the body’s circulation behave like a SERIES circuit?
If so, why is it important?
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
What are low pressure, low resistance vs. high pressure circulation systems, low pressure?
Low pressure, low resistance: Pulmonary circuit
High pressure: Systemic circuit
What are the distributing, exchange and collecting vessels?
distributing vessels: arteries
exchange vessels:capillaries
collecting (capacitance) vessels: veins
Is CO the same for both ventricles?
Yes!
Volume of blood is same for both ventricles
Flow (as a % of CO) is highest for what organ?
Lungs!
What is most important for adjusting CO?
Venous reservoir!
Systemic vascular resistance (total peripheral resistance) is highest in what type of blood vessels?
small arteries and arterioles (changes in vascular tone adjusts flow!)
CO = ____________ return?
CO = Venous Return
What does flow to a region depend on?
Regional resistance and Cardiac output
Which blood vessels have the largest cross sectional area and the lowest velocity?
Capillaries = largest cross sectional area, lowest velocity
What are the elements of resistance that affect flow? (according to Poiseuille’s law)
pressure gradient
vessel radius
fluid viscosity
tube length
What is the formula for total peripheral resistance (systemic vascular resistance)?
TPR = (Aortic P - CVP)/CO
What is he formula for pulmonary vascular resistance?
Pulmonary vascular Resistance = (PAP-LAP)/CO
Is pulmonary artery resistance less than 1/10th of systemic vascular resistance?
Yes!
Where is the largest pulse pressure and what is it?
in LV = 120/9
What happens to mean pressure as blood flows from the aorta to arteries, capillaries, veins to RA?
It falls
same pattern of falling pressure also occurs in pulmonary circulation!
Catheters can be used to directly measure what?
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
Filling pressure for the left atrium is also known as what?
Pulmonary capillary wedge pressure
How do you measure CO?
indicator dilution (Indicator injected/Mean dye conc x duration of 1st circulation) where Mean dye conc = temp deflection
or thermal dilution techniques
How does the Fick principle contribute to measure CO?
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.
Can you express resistance as a function of flow and change in pressure?
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
What’s the difference between laminar vs. turbulent flow?
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
What things cause turbulence?
high velocity flow in tube with uniform caliber
local obstruction
abrupt increase in caliber
local obstruction + increased caliber
What’s the formula for wall tension?
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
Do smaller vessels (microcirculation = arterioles, metaarterioles, capillaries, venules) have low wall tension and high pressure?
Yes! Small radius so low wall tension and high pressure
Can Vascular disease lead to aneuyrism (increased radius) and rupture due to higher wall tension?
Yes!
Pouiselle’s law relates to Resistance. You can use it, e.g., in parallel circuits. What is the formula?
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.
