Circulation Flashcards
what is normal arterial blood pressure
120mmHg (systolic)/ 80mm Hg (diastolic)
What is the BP by the time it reaches the termination of the vena cava
0
What is systemic capillary pressure
From 35mmHg to 10 mmHg
What is systolic pulmonary artery pressure
25mm Hg
What is diastolic pulmonary artery pressure
8mm Hg
What is the function of arterioles
control conduits
What is the function of capillaries
exchange between blood and extracellular fluid
What percentage blood is in the systemic circulation
84 %
what percent of blood is in the veins
64%
What percent of blood is in the arteries
13%
What percent of blood is in the systemic arterioles and capillaries
7%
What percentage of blood volume is in the heart and lungs
16%
What percentage of blood is in the pulmonary circulation
9%
What percentage of blood is in the heart
7%
The velocity of blood flow (v) is inversely proportional to what
vascular cross-sectional area (A)
What is the equation for velocity of blood flow
V=F/A (F= volume of blood flow)
what is the velocity of blood in the aorta when at rest
33cm/sec
What is the velocity of blood at the capillaries when at rest
0.3mm/sec
What is the cross-sectional area of the aorta
2.5cm squared
What is the cross-sectional area of small arteries
20 cm squared
What is the cross-sectional area of Arterioles
40 cm squared
What is the cross-sectional area of Capillaries
2500cm squared
What is the cross-sectional area of Venules
250 cm squared
What is the cross-sectional area of small veins
80 cm squared
What is the cross-sectional area of Vena Cavae
9 cm squared
What are the three functional principles of the Circulatory system
- Rate of blood flow to each tissue of the body is almost always precisely controlled in relation to the tissue need.
- The cardiac output is controlled mainly by the sum of all local tissue flows
- Arterial pressure regulation is generally independent of either local blood flow control or cardiac output control
In each tissue what monitors tissue needs
Microvessels
O2, other nutrients, CO2 accumulation, tissue waste product accumulation at directly on what
local blood vessels and dilate or constrict accordingly
The heart responds to demand of _____
Tissues
____ may be needed to help the heart pump required amount of blood
nerve signals
Explain the nervous reflex if the arterial pressure falls below 100mm Hg
increase force of heart pumping
constrict large venous reservoirs
Generally constrict most of the arterioles throughout the body (increases arterial pressure)
Kidneys may later play important role in pressure control
What are two factors determining blood flow
Pressure gradient- pressure difference between the two ends of a vessel
Impediment to blood flow though the vessel (resistance)
Flow is directly proportional to _______ but inversely proportional to ______
Pressure difference, resistance
The flow through a vessel can be calculated by ____ (_____)
ohm’s law (poiseuille equation)
Flow is directly proportional to what
pressure difference
Flow is indirectly proportional to what
Resistance
What is poiseuille’s equation
Force= change in pressure/Resistance
Poiseuille’s equation can be applied to…..
a single vessel, an organ, or an entire circuit
Blood flow is usually expressed as
ml/min or liters/min
The overall blood flow of an adult at rest is on average
5000 ml/min or 5 liters/min this equals the cardiac output
Is the cardiac output equal to the average overall blood flow of an adult at rest
Yes
Laminar blood flow is equal to what
streamline flow
laminar blood flow means that blood flows at a steady _____ and in
Rate, in layers
Laminar blood flow means the vessel is ___ and ___
long and smooth
In laminar blood flow does each layer maintain the same distance from the vessel wall
yes
in laminar blood flow the velocity of fluid flowing in ______ is greater than that of the fluid flowing toward _______
Center, outer edges
Turbulent flow creates what
Murmurs
Does turbulent flow form layers
No
Which is more resistant turbulent flow or laminar flow
Turbulent
When does Turbulent flow occur
when flow is too great
when blood passes an obstruction within the vessel
When blood has to make a sharp turn
When blood passes over a rough surface
What is Turbulent flow
When blood flows in all directions in the vessel and continually mixes within the vessel.
What are eddy currents
similar to the whirlpools that one frequently sees in a rapidly flowing river at a point of obstruction
When present the blood flows with much greater resistance than when the flow is streamlined, eddies add tremendously to the overall friction of flow in the vessel
Tendency for turbulent flow increases in direct proportion to?
Velocity of blood flow
diameter of the vessel
Density of the blood
Tendency for turbulent flow is inversely proportional to
Viscosity of blood
Is blood heavier than water
yes
Specific gravity of blood is
1.055
Blood density depends on the proportion of
its components and in particular of red blood cells and proteins
Is blood more viscous than water
Yes
The relative value of blood viscosity is what, when compared t the viscosity of water
4.5
Blood _______ is the property of blood to adhere to vessel walls and to each other and is based on the number, shape, and size of red cells
Viscosity
Viscosity ensure ______ of blood through the vessels
Laminar flow
What is Reynolds number
it is a measure of the tendency for turbulence to occur
What is the equation for Reynold’s number
Re= (VxDxP)/n
n=viscosity (in poise)
What is the normal blood viscosity in poise
1/30 poise
The density of blood is normally
only slightly greater than 1
When Re rises above ______, turbulent flow will occur in some regions of a vessel
200-400
When Re rises above _____, turbulence will occur even in a straight vessel
2000
Blood pressure measures
The force exerted by the blood against any unit area of the vessel wall
Blood pressure can be measured with
mercury manometer or with electronic transducers
___________ is the impediment to blood flow in a vessel
Resistance
Resistance must be indirectly calculated from measurements of _____ and _____
blood flow and pressure
Resistance equation in terms of blood
R=Pressure/volume/time
What is a PRU
Peripheral resistance unit
What are the three major variables that determine resistance
Vessel radius, Blood viscosity, Vessel Length
What is the most important of the 3 major variables determining resistance
vessel radius
R=?
R=8nl/3.14(r^4)
n= visocosity of blood
l= length of vessel
What vessels have the largest pressure drop
Arterioles
Why do arterioles have the largest pressure drop
they have the highest resistance
There is a low pressure drop across the major arteries due to what
they have low resistance
pulse pressure is the difference between ___ and ___
Systolic and diastolic pressure
Systolic pressure is the _____ arterial pressure duing a cardiac cycle
Highest
Diastolic pressure is the _____ arterial pressure
Lowest
Systolic pressure is measured after _____
Systole
Diastolic pressure is measured when
the hear is relaxed (diastole)
What is the Rate of blood flow though the entire circulatory system
100ml/sec
What is the pressure difference from systemic arteries to systemic veins
100 mm Hg
What is the resistance of the entire systemic circulation
Rate of blood flow/pressure difference= 100/100=
1 PRU
In conditions when the vessels are strongly constricted, total peripheral resistance may rise to ___ PRU
4
When vessels are greatly dilated, the resistance can fall to as little as ___ PRU
0.2
What is the average mean pulmonary arterial pressure
16 mm Hg
What is the mean left atrial pressure
Averages 2 mm Hg
What is the average resistance of the pulmonary system when cardiac output is the normal 100ml/sec
0.14 PRU
_______ is the measure of blood flow through a vessel for a given pressure difference
Conductance
Conductance is the exact reciprocal of what
Resistance
Conductance is directly proportional to what
Diameter^4
A fourfold increase in vessel diameter can increase the flow by as much as what
256x
Arterioles, with only a minor change in diameter, can cause a vast _______ in blood flow
Increase
Conductance is usually expressed in what
ml/sec per ml Hg
Blood vessels branch extensively to form ____ circuits that supply blood to the many organs and tissues of the body
Parallel
The total resistance of blood vessel branches is far ____ than the resistance of any single blood vessel
less
The total conductance of vessels arranged in parallel is the ____ of the conductance of each parallel pathway
sum
Name the 6 circulations arranged in parallel
Brain Kidney Muscle Gastrointestinal Skin Coronary Circulation
Removal of a limb or removal of a kidney removes a parallel circuit and results in
Reduces total vascular conductance
Reduces total blood flow
Increases total peripheral vascular resistance
_____ is a measure of the fluid’s internal resistance
Viscosity
The greater the viscosity, the great the
Resistance
What is the prime determinant of blood viscosity
Hematocrit
The viscosity of normal blood is about ____ times as great as the viscosity of water, mostly because of the large numbers of
3, suspended red blood cells
What is the normal hematocrit of adult men
42
What is the normal hematocrit of adult female
38
When the hematocrit rises to 60-70 what is this called
polycythemia
when the hematocrit rises to 60-70 what is the viscosity
about 10
What is the viscosity of blood plasma w/o RBCs
1.5 that of water
What effect does anemia have on viscosity
it decreases it
What effect does polycythemia have on viscosity
it increases it
Autoregulation of blood flow occurs between
changes in arterial pressure between 70 ad 175 mm Hg
Explain tissue blood flow autoregulation
The ability of each tissue to adjust its vascular resistance and to maintain normal blood flow through changes in arterial pressure between approximately 70 an 175 mm Hg
Sympathetic innnervation effects ______ and effects arterial pressure
vascular tone
as sympathetic stimulation increases so does
arterial pressure
