Exam 1 Content Flashcards
How does ADH affect free water clearance?
Renal Review
Clearance, Free Water Clearance
-Clearance: How much (volume) of plasma is cleared of a substance per unit/time
-Free water clearance: Refers to the volume of water being removed from the body per unit time.
If our ADH is high, free water clearance will be low
If ADH is low, free water clearance will be high
Free water clearance does not take into account electrolytes or any dissolved substances
Normal BP, MAP, MAP equation
Normal Pressure Values- Systemic Circuit
-Normal BP is SBP 120/80 DBP
-Estimate of normal MAP is 100mmHg
-MAP= DBP + 1/3 (SBP-DBP)
Gives us a MAP of 93mmHg w/ a normal BP
Vascular Resistance & Hydrostatic Pressure- Systemic Circuit
High resistance arterioles, pressures throughout the systemic circuit
-Arterioles are high resistance vessels
-Arteries upstream from the arterioles will be high
-Arteries downstream from the arterioles will be low
-Aorta is the source of the blood, the further we move away from the source, the lower the pressure becomes
-Capillary BP on arteriole end; 30mmHg
-Capillary BP on venous end; 10mmHg
-As we move closer to the R. Atrium (furthest point from Aorta, end of systemic circuit) pressure becomes 0mmHg
DeltaP of systemic circuit: 100mmHg-0mmHg
Vascular Resistance- Pulmonary Circuit
-Pulmonary arteriole pressure (PAP, MPAP): 16mmHg
-Reasonable BP for P.A 25/8 (does not calculate to 16mmHg)
-L. Atrium (end of pulmonary circuit) pressure should be 2mmHg
DeltaP of pulm circuit: 16mmHg- 2mmHg
How does compliance effect pulse pressure? & S.V?
Pulse Pressure- Systemic
Which type of artery has a higher pulse pressure than the aorta?
-PP is equal to the difference between SBP and DBP
-Pulse pressure near the aorta should be ~40mmHg
-Narrowing of pulse pressure: As blood is moving through an area of high resistance, pulse pressure is typically reduced (consequence of energy being used to move through the vasculature)
-Widening of pulse pressure: Typically happens in large arteries such as the femoral artery.
Why? Large arteries have less compliance; the more fluid that is pumped into this container, the higher the pressure will be
An increase in S.V should increase P.P.
Compliance and PP are inversely related
Pulse Pressure- Pulmonary Circuit
-PP is much less than in the systemic circuit
-Pulmonary vessels are 1. low resistance and 2. high compliance
How does blood get pumped through the systemic circulation during diastole?
What happens to the aorta’s ability to stretch as we age?
-The aorta has a high compliance; it’s job is to stretch to accomodate a large amount of volume being pumped from the heart during systole.
During diastole, the walls of the aorta come closer together, acting as a secondary heart pump, pushing the blood downstream
As we age, the aorta becomes less compliant causing a higher pulse pressure
Conductance, Diameter, & Resistance
-The single most important variable that controls conductane of blood flow is increases or decreases in resistance that occur due to vasoconstriction or relaxation
-A small change in diameter results in a huge change in resistance, and therefore, blood flow
-Resistance and flow are related to diameter to the 4th power
Equations
Vascular Compliance
Vascular Distensibility
Delta P/ Blood Flow/ Resistance
Conductance
Compliance: Delta V/ Delta P (mmHg in CV system, cmH2O in pulm)
Distensibility: Delta V/ (Delta P X Original Volume)
Distensibility = Expandibility
Delta P: F x R
F: Delta P/ R
R: Delta P/ F
Conductance: 1/Resistance
Conductance is inversely related to resistance
Pressure in the LA? The LV? LV pressure needs to be higher than what?
What about the RV?
-L.A pressure is ~2mmHg
-There is a wide range of pressures in the L. V. During diastole, pressure in the L.V should be pretty low because there is no squeeze.
During contraction, the pressure in the LV will rise significantly. The pressure in the LV needs to be higher than the pressure in the aorta during systole in order to eject blood into the aorta
-During diastole, the RV is going to have a low pressure.
During systole, the pressure can rise up to ~25mmHg
Velocity is dependent upon what?
Velocity & Blood Flow
the larger the cross-sectional area…
CO: 5l/min (HR x SV)
Velocity of blood flow is depended upon the cross-sectional diameter of the blood vessel
The larger the cross-sectional area, the slower the blood flow
Isogravometric point? Effect on measuring BP in upright position?
Gravity & It’s Effects on BP
Why is the pressure 0mmHg in the neck?
Pressure in the sinuses? What happens when exposed to air?
-Isogravometric point (phlebostatic axis): The point at which gravity has no effect on pressure because this point is located in the center of the pressure source (the tricuspid valve)
-As we move further below the isogravometric, the pressure will rise
-As we move further above the isogravometric point, the pressure will decrease
-The pressure in our neck is 0 because the veins are wide and thin-walled. These veins would collapse if there was a negative pressure
-The sinuses in the brain are very rigid, so when placed in an upright position, the pressure in these sinuses is subatmospheric. If this sinus is exposed to air, it will suck air in because of the negative pressure
How do we do this?
Measuring the effect of gravity on fluid
-Going 13.6mm below a source of pressure will give us a 1mmHg rise in pressure
The further below the source of pressure, the higher the pressure will be
-13.6mm = 1.36cm
Pressure changes in arteries w/ & w/o gravity
-Without the effect of gravity, pressure in the arteries should remain consistent until the arterioles (~100mmHg)
-With the effect of gravity, blood pressure is a combination of pressure generated by the heart plus the pressure that is a result of gravitational effects on the blood
Valves combat …? What happens as we age?
Take note of pressure differences in veins
-Veins have one-way valves that combat the effects of gravity. The valves prevent retrograde flow of blood, and promote blood return to the heart. Functioning valves also keep the pressure in the lower extremities from rising
-As we age, the valves begin to separate and do not prevent retrograde blood flow. This leads to higher pressures in the veins eventually causing varicose veins.
-Valves and veins rely on skeletal muscle contraction in order to effectively push blood back to the heart
Note what is happening w/ sympathetic inhibition & stimulation
Behavior of Vessel Walls
- ~700ml of fluid is found in our systemic arterial circulation at all times
- Arterial system operates at higher pressures with less volume (less compliant)
- Sympathetic Inhibition in arterial system w/ same amount of volume: blood pressure will decrease significantly
- ~2500ml of fluid is found in our systemic venous system at all times
- Venous system operates at a lower pressure with higher volume (more compliant)
Slope of the line is an estimate of compliance when the graph is set up with pressure on the side axis and volume on the bottom axis
What is it? Turbulent flow is associated with what?
Reynold’s Number & Turbulent Flow
Arteries at risk for turbulent flow? Veins?
-Reynold’s number is a theoretical, unitless number that describes the chances of experiencing turbulent flow
-If the number is >2000, that means there will be turbulent flow
-Turbulent blood flow means there is blood flow moving in all different directions, wasting massive amounts of energy, and creating a high risk for blood clots. Turbulent flow is associated with volume, meaning you can hear the flow
V= Velocity
D= diameter
P= Density
N= Viscosity
An increase in V, D, or P will increase risk for turbulent flow
An increase in viscosity will decreased risk for turbulent flow
Aorta and large arteries closest to the heart are at the greatest risk for turbulent flow.
Venous system has a very low velocity, so there is hardly any risk for turbulent flow
Flowmeters & Pressure Transducers
Flowmeters:
-Electromagnetic probe that fits around a blood vessel. Measures the flow through the flowmeter in the probe by looking at the magnetic effect created by the iron in Hgb
-Ultrasonic flowmeter; has to be implanted & wrapped around a blood vessel
-Lasers; have imbedded senors that look at the light that’s being reflected from blood. Higher flow = different reflection
Pressure Tranducers:
- Blood flows through a needle/catheter connected to the CV system into the chamber tray. Within the chamber, there is a small electromagnetic probe that senses changes in pressure
Pressure Volume Loop- Period of Filling (I)
- Begins with the ESV (50mls) leftover from the previous cardiac cyle.
- Filling is primarily passive and dependent on preload. L. Atrial pressure is low (~2mmHg) until the ventricle reaches ~110ml.
- L. Atrium contracts –> remaining 10ml fills the ventricle –> EDV = ~120mls
-Atrial kick becomes very helpful when there is cardiac pathology. A sick heart may be dependant on the atria for atleast 25% of ventricular filling
Systole begins after the mitral valve closes
?
Pressure Volume Loop- Isovolumetric Contraction (II
-Very short in time
-Ventricle begins to contract –> left ventricular pressure becomes higher than left atrial pressure causing the mitral valve to close
-Aortic valve remains closed at this time
-Both valves are closed at this time, the volume remains the same; however pressure increases due to ventricular contraction. This causes the line on the graph to be straight up and down
-If there were valvular disease and valves could not close all of the way, that would change the slope of the line
-Pressure in the ventricle exceeds the pressure in the aorta, aortic valve opens
Pressure Volume Loop- Period of Ejection (III)
-Aortic valve opens; this is our DBP
-Blood is ejected from the ventricle into the aorta
-The difference in volume from the beginning of phase III to the end of phase III is our stroke volume (EDV - ESV =SV)
-Aortic pressure is at it’s highest, higher than the L. ventricular pressure –> aortic valve closes. SBP is measured here
Diastole begins here when the aortic valve closes
Pressure Volume Loop- Isovolumetric Relaxation (IV)
-Aortic and mitral valves are closed
-Intraventricular pressure begins to decrease
-Once intraventricular pressure is lower than L. atrial pressure, mitral valve opens and phase IV ends
-Volume remains the same
ECG: Depolarization happens first, then the physical force generated happens second
-QRS happens –> ventricular pressure increases
-Diastole begins when the aortic valve closes at the end of Phase III, and ends at the end of phase I
-Systole begins at the beginning of phase II, after the mitral valve has closed, and ends at the end of phase III
-The ventricle is filled during phase I, and blood is ejected in phase III.
-The vast majority of the filling is done in the first 1/3rd of ventricular filling
This graph is showing how the pressure volume loop can shift depending on stretch and volume of the heart