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71 Cards in this Set
- Front
- Back
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Something we know for sure about cardiac output:
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Whatever the left side pumps out equals what the right pumps to the lungs.
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What is left heart output?
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Systemic bloodflow
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What is right heart output?
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Pulmonary bloodflow
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What is "stressed" blood volume?
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The blood in the systemic ARTERIES
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Where is the site of highest resistance in the CV system?
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The arterioles
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What else is important about the arterioles?
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That is where autonomic regulation of bloodflow occurs!
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2 types of autonomic receptors on the arterioles:
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-alpha1 Adrenergics
-B2 adrenergics |
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What arterioles have a1 receptors?
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Skin
Splanchnic (gut) Renal |
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Where are there B2 receptors on vessels?
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Muscle
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What vessels have the largest cross-sectional SA?
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Capillaries
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Major difference between Veins and Arteries:
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Arteries - HIGH pressure
Veins - LOW pressure |
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What is important about the veinous blood content?
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The veins have the HIGHEST proportion of the body's total blood!
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What is the volume in the veins called?
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Unstressed volume
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So what is stressed and what is unstressed blood volume?
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Stressed = in arteries
Unstressed = in veins |
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Is the veinous circulation regulated autonomically?
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YES! By a1-adrenergic receptors
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How do we calculate bloodflow VELOCITY?
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v = Q/A
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What is Q/A?
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Q = blood flow
A = cross sectional area |
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So where is the highest vs lowest flow velocity?
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Highest velocity - Aorta
Slowest velocity - Capillaries |
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How do we calculate Bloodflow?
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Q = Pdiff/R
-Pressure gradient -Resistance |
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What is the pressure gradient and resistance that we're talking about when we calculate Cardiac output?
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Pressure diff = the difference between MAP and RAP
Resistance = total periph R |
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So how do we calculate CO?
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CO = (MAP-RAP)/TPR
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What is the physics equation that CO is analogous to?
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Ohm's law - V=IR or I=V/R
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What equation calculates RESISTANCE?
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Poiseuille's equation
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What is Poiseuille's equation?
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R=8nl/pi(r^4)
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What's the REALLY important part about poiseulle's equation?
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1/r^4 - very small changes in the RADIUS of a vessel will produce significant increases in resistance!
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What is the n part?
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Viscosity
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How do we change viscosity?
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Change the hematocrit
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How will decreasing a bloodvessel's radius by a factor of 2 change bloodflow?
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2^4 = 16; resistance increases 16X so bloodflow decreases 16X
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What are the 2 types of resistance that circulation encounters?
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-Parallel
-Series |
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Where do we see resistance in parallel?
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In the systemic circulation - each organ presents resistance in parallel
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How does parallel resistance affect total peripheral resistance, and how does it affect the pressure across each organ?
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TPR is DECREASED by resistors in parallel; there is NO change in pressure across each organ.
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Where is Series resistance illustrated in the body?
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In the circulation WITHIN each organ - arteries become arterioles, then capillaries, veinules, then veins.
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What happens to resistance as it encounters each resistor in a series? How does this affect the pressure gradient across the organ?
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Resistance INCREASES with each resistor; the overall pressure gradient is HIGHER because pressure decreases.
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Where is the LARGEST contributor to resistance in series?
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ARTERIOLES
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What are 2 'types' of flow thru a vessel?
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Laminar (streamlined) and Turbulent
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What number predicts whether bloodflow will be laminar or turbulant?
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Reynold's!
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What does an INCREASED Reynold's number indicate?
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Higher tendency for turbulance
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What will increased turbulence in vessels cause?
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Bruits
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What 2 factors increase turbulence?
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1. Increased blood VELOCITY
2. Decreased blood VISCOSITY |
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What are 2 CLINICAL things that will thus increase blood turbulence?
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1. Anemia (lower viscosity)
2. Narrowing of a vessel |
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What describes a blood vessel's DISTENSIBILITY?
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Compliance
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Compliance is aka
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Capacitance
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What is Capacitance inversely ppl to?
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Elastance
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How do we remember the relationship between Capacitance and Elastance?
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Think of emphesyma - they have loss of alveolar ELASTICITY so increased DISTENSIBILITY (capacitance)
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What does capacitance really describe?
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How much volume can increase w/ a change in pressure
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What vessels have the highest capacitance?
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VEINS - that's why they hold a loooot of volume but are LOOOW pressure (unstressed)
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How can we change the capacitance of a vessel?
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By stimulating the a1 adrenergic receptors.
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How does SNS stimulation of the vessels affect blood volume in general?
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Decreases capacitance of the VEINS so the UNstressed volume shifts into the stressed volume.
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How does arterial capacitance change with age?
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It DECREASES - the arteries become STIFFER and LESS distensible
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How does blood pressure change as blood flows through the systemic vessels?
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It decreases
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Pressure in:
-Aorta/arteries -Arterioles -Capillaries -Veins |
Aorta=100
Arterioles 50 Caps 20 Veins 4 |
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What are 3 things that will increase the hematocrit and thus decrease bloodflow based on poiseuilles law?
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-Polycythemia vera
-Multiple myeloma/increased proteins in blood -Hereditary spherocytosis |
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interesting
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yep
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What is the highest vs lowest arterial pressure during a cardiac cycle?
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Systolic - highest
diastolic - lowest |
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When is systolic pressure measured?
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After the heart contracts and ejects blood into the aorta
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When is diastolic pressure measured?
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When the heart is relaxed and blood is returning to the heart in the veins
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What is the Pulse Pressure?
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The diff between Systolic and Diastolic
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What is the most important determinant of PP?
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Stroke VOLUME!
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Why does arterial pressure increase so much after systole?
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Because capacitance in arteries is LOW so the increase in volume causes a huge increase in pressure
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What will cause pulse pressure to increase even more?
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Aging - decreases capacitance of the arteries so the heart's stroke volumes will produce even higher pressure in the arteries
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And why is the vein pressure so low?
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Because they have HIGH capacitance
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What is the pressure in the heart ATRIA like?
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Even lower than in the veins!
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How is Left atrial pressure measured?
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With a swan-ganz catheter pulmonary wedge
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What does a pulmonary wedge pressure measure?
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The pulmonary CAPILLARY pressure which is approx the same as left atrial pressure
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What is the pressure in the RA?
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<4
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What is the pressure in the RV?
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25/5
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What is the pressure in pulmonary arteries?
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25/10
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What is the pressure in pulmonary CAPS? What is this?
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PCWP - <12 - Left atrial pressure
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So what is the LA pressure?
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12
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What is the LV pressure?
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130/10
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What is the aortic pressure?
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120/80
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