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45 Cards in this Set
- Front
- Back
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3 characteristics of Arteries
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High pressure
Rapid flow Strong walls |
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Pressure in 3 dif arteries
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Aorta- Mean systemic arterial pressure = 100 mmHg
Peripheral arteries= 120/80 Pulmonary arteries= 25/8 |
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What are the 2 effects of changing the arteriole diameter?
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1. Constriction increases AP but decreases capillary and venous pressure
2. Dilation decreases AP but increases organ perfusion and capillary pressure -promotes perfusion |
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Capillaries
aka how do they work |
exchange vessels
largest total cross sectional and surface area velocity of flow is proportional to 1/ cross sectional area the larger the area, the slower the velocity of flow at a certain pressure |
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Venules
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Collect blood from capillaries
They are very small and form larger veins |
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Veins
aka |
capacitance vessels
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Blood reservoir
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peripheral venous pool
combined venous volumes of the systemic organs |
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sympathetic stimulation on veins
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veins constrict and empty blood into a central venous pool
(thoracic veins and right atrium) which increases venous return and helps stroke volume |
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What are microvessels
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they monitor the demand for oxygen, nutrients, and waste product accumulation
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Autoregulation
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local blood flow is controlled to the desired level of activity
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What is CO controlled by
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the sum of all local tissue flows
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What is arteriole pressure independent from
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its independent of local blood flow and CO
it varies between 120/80 |
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Difference bt systolic and diastolic pressure ___ with the distance from the heart in large arteries
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increases
(as pulse pressure increases, difference bt systolic/diastolic increases) |
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Pressure gradient within a vessel is controlled by 2 factors
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Blood flow
Vascular resistance |
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What are 2 types of blood flow?
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Laminar flow (streamline)
Turbulent flow |
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2 characteristics of laminar flow
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each layer of blood stays same distance from wall
central portion of blood stays in center and has the highest velocity |
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What is turbulent flow
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flow in all directions with mixing
Eddy currents (flow around obstruction, turns, rough surfaces) cause increased resistance |
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Tendency for turbulence is directly proportional to 2 things
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1. velocity of flow: velocity increases, turbulence increases
2. vessel diameter: diameter increases, turbulence increases |
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indirectly proportional to
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Fluid viscosity
as viscosity increase, turbulence decreases |
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Resistance to flow
what increases and decreases it |
Total peripheral resistance (TPR)
Vasoconstriction increases TPR 4 fold Vasodilation decreases TPR 20% |
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where is 2/3 of TPR
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in arterioles
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Poiseuille's law
what factors affect resistance |
Length
Viscocity Vessel Diameter |
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Hematocrit
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% of blood that is RBC
nonlinear increase in viscosity with increased hematocrit |
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vessel diameter
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D= 2 X radius
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Radius/2
Radius X 2 vessel diam increased 4- fold |
flow decreases 16-fold
flow increases 16 fold flow increased 256 fold |
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Effect of arterial pressure on flow
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Increased AP increases blood flow in 2 ways
-increases delta p -distends vessels and lowers resistance |
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Sympathetic stimulation
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decreased symp stimulation will decrease tone- vasodilation
(increases diameter, increases flow) |
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Vascular distensibility
-what are the most distensible how much? |
Veins are the most distensible vessel
(veins 8x more distensible than systemic arteries) |
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distensible x volume
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compliancy
veins 24x more compliant than arteries |
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what is the aortic pressure wave
3 steps |
1. left ventrical SV empties into aorta during systole
2. part of energy of ventricular contraction provides forward flow during systole, the rest is stored as potential energy 3. stored potential energy is released by recoil of the aortic wall and propels the blood (diastolic runoff) |
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What is the presence of incisura in the arterial system
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aka dicrotic notch
-short period of backflow of blood before aortic valve closure (lowers pressure) -then backflow suddenly stops (raises pressure) |
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Peripheral pressure waves
Descending aorta vs ascending aorta |
systolic pressures are higher
diastolic pressures are lower in the descending aorta and lg arteries |
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what happens to the incisura as you move further from the heart
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is becomes less sharp and the dicrotic waves will appear
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What happens as blood moves towards the distal arteries?
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SBP increases
DBP decreases PP increases MSAP decreases slightly |
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What happens when flow reaches the capillaries?
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pulsatile characteristics virtually gone; continuous tissue flow
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What happens to pulse pressure as you age?
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in increases with age due to decreased arteriole compliance (arteries get hard)
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Atherosclerosis
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noncompliant arteries
increases systolic |
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Aortic stenosis
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decreases systolic bp due to decreased flow
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aortic regurgitation
what is it |
dysfunctional aortic valve
blood pumped into aorta during systole will flow back into LV during diastole |
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aortic pressure during diastole
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0
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what does aortic regurgitation cause
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increases left ventricular blood volume and SV
-raises BP during systole |
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Venous pressure
how is RAP determined |
Right arteriole pressure determined by balance bt R atrial pumping and venous return
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Large veins and resistance to flow
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Lg veins are usually compressed so they usually have resistance to flow
Creates peripheral venous pressure in smaller veins (greater than RAP) |
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What happens if RAP increases to match the venous pressure
what happens if its increased more than venous pressure |
blood will back up in large veins and the collapsed points will open
the peripheral venous pressure will increase |
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Feet venous pressure
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25 instead of 90 due to hydrostatic forces
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