Phys: The Heart As A Pump Flashcards
**just fyi…know the circuit of the heart pump and flow
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What is constant in normal intact circulation?
Total blood volume
An increase in the volume of blood in one area must be accompanied by what..?
A decrease in blood volume in another area
What determines the distribution of blood circulating to the different regions of the body?
-output of the left ventricle
-the contractile state of the resistance vessels (arterioles)
Blood vessels serve as a ________system of passive conduits that delivers blood to and from the tissue
Closed
Blood vessels participate ___________ in the regulation of blood flow to the organs.
Actively
What happens when resistance in the blood vessels (particularly arterioles) is altered?
Blood flow to that organ is altered
The aorta is made up of primarily what tissue?
Elastic tissue
What are the most muscular vessels?
Arterioles
In the large arteries, frictional resistance is relatively _______ and pressures are _______________ than those in the aorta
Small, slightly less
Maximum resistance of blood flow occurs in which vessels?
Arterioles
Where in the vessels is pressure drop the greatest?
The terminal segment of small arteries and arterioles
Is capillary blood flow pulsatile or non-pulsatile?
Non-pulsatile
What progressively dampens pulsatile pressure?
-elasticity of arterial walls
-frictional resistance of small arteries and arterioles
Characteristics of arteries:
-thick walled
-elastic
-highest pressure
Characteristics of arterioles:
-smooth muscle
-highest resistance to blood flow
-alpha 1 receptors
-beta 2 receptors
What does alpha 1 cause in the arterioles?
Contraction or constriction of the vascular smooth muscle
What does beta 2 cause in the arterioles?
Cause dilation or relaxation of vessels in the skeletal muscle
How do arterioles change resistance in the vessels?
Through sympathetic nerve activity via Catecholamines and other vasoactive substances
What is the structure of capillaries?
Thin-walled and lined with a single layer of endothelial cells
Where does the greatest pressure drop occur?
Arterioles
What occurs in the capillaries?
-gas exchange
-is a site for nutrients
Characteristics of veins and venules:
-thin-walled
-endothelial cells layer
-modest amount of elastic tissue, smooth muscle, and skeletal muscle
-large capacitance
-alpha 1 receptors
What is cardiac output?
The rate at which blood is pumped from either ventricle
What is it called when the cardiac output of the left and right ventricle are equal?
Steady state
The left and right heart operate in a ________ meaning that…
Series, venous return to left heart equals venous return to right heart
What is blood flow?
The quantity of blood that passes a given point in the circulation in a given period of time
Units for blood flow:
mL or L
Overall blood flow in an adult:
5L/min (which is the cardiac output)
What does Q stand for?
Flow through a blood vessel
Equation for blood flow:
Q = deltaP/R
Delta P is the…
Pressure difference between the two ends of the vessel
R is the…
Resistance of the vessel
What is laminar flow?
When blood moves smoothly in parallel layers through the blood vessel at equal distances from the wall
What happens to the velocity of blood in laminar flow?
The velocity in the center of the vessel is greater than the velocity in the outer edge
The difference in velocities throughout the blood vessel creates a _________profile
Parabolic profile
What is turbulent blood flow?
Chaotic blood flowing in an unorganized pattern through the vessel
Causes of turbulent blood flow:
-high velocities
-sharp turns in circulation
-rough surfaces in circulation
-rapid narrowing of blood vessels
Turbulent blood flow tends to cause _______
Murmurs
What are murmurs or bruits important in diagnosing?
-vessel stenosis
-vessel shunts
-cardiac valvular lesions
What are palpable murmurs called?
Thrill
What is the name of the equation that determines the resistance of a blood vessel to blood flow?
Poiseuille equation
Resistance to flow is directly proportional to ______ ______ and ______
Blood viscosity and length
Resistance to flow is inversely proportional to the ___________
Fourth power of the radius
Is conductance sensitive to change in diameter of the vessel?
YES, very sensitive
What is conductance directly proportional to?
The fourth power of the radius
The circulatory system is arranged in both ______ and in ________
Series and in parallel
Where do series arrangements of circulatory system occur?
Within an organ
Where does parallel arrangement in circulatory system occur?
Multiple organs
Capillaries have the highest ________________and lowest __________
Cross sectional area, flow velocity
What accounts for most of the total peripheral resistance?
Arterioles
What provides most of the blood storage capacity?
Veins
What does viscosity depend on?
Hematocrit
What is blood pressure?
The force exerted by the blood against any unit area of vessel wall
The top number in blood pressure is the ______ pressure
Systolic
The bottom number in blood pressure is the ______ pressure
Diastolic
Incisura:
Backflow of blood to close aortic valve
Pulse pressure is the difference between what?
Systolic and diastolic pressure
What is mean arterial pressure?
Average pressure during a complete cycle adn is the driving force for blood to flow to organs and capillaries
What is used to measure left atrial pressure and why?
Pulmonary wedge pressure, because pressures on the left side of heart are more difficult to measure directly
What is used to measure pulmonary wedge pressure?
Pulmonary artery catheter
What is vascular distensibility?
Blood vessel can expand in response to a change in pressure
Veins are ___ times more distensibility than arteries
8x
What is Vascular compliance/capacitance?
Ability of a blood vessel to expand and hold in more volume in response to an increase in pressure
*considers absolute change
The capacitance of veins is ____ times that of arterioles
24x
Effect of aging on artery compliance:
-wall characteristic change with age
-walls become stiffer
-arterial pressures increased
Factors that affect pulse pressure:
-increase stroke volume decrease pulse pressure
-decrease in arterial compliance increase pulse pressure
**or vice versa for both
Arteriosclerosis:
-Plaque deposits in arterial walls that cause a decrease in the diameter of the of the arteries and make them stiffer and less compliant
-arteriosclerosis INCREASE pulse pressure
Aortic stenosis
-reduced size of aortic lumen which decreases stroke volume and pulse pressure
What is pressure in the right atrium called?
Central venous pressure
What regulates right atrial pressure (or central venous pressure)?
A balance between the ability of the heart to pump blood out of the atrium and the rate of blood flowing into the atrium from peripheral veins
Factors that increase central venous pressure:
-increased blood volume
-increased venous tone
-dilation of arterioles
-decreased cardiac functin
What direction does blood flow?
From higher to lower pressure
When is the cardiac cycle initiated?
With firing of SA that stimulates the atria to fire
ESV (end sytostolic volume):
Blood that remains after systole
EDV (end-diastolic volume) =
Blood that remains at the end of diastole
Cardiac output equation:
CO = stroke volume X heart rate
Ejection fraction is an index of _________ __________
Ventricular contractility
Ejection fraction equation:
EF = (EDV-ESV/ EDV) X100
What does the P wave represent?
Atrial depolarization
What does the QRS complex represent?
Ventricular depolarization
What does the T wave represent?
Ventricular repolarization
Order of speed of conduction:
His-purkinje -> Atria -> ventricles -> AV node
PR interval =
0.12-.20 seconds
QRS interval =
0.08 and 0.10 seconds
QT interval =
0.4 to 0.44 seconds
Systole is a period of ___________
Contraction
Diastole is a period of ___________ where the heart _________________
Relaxation, fills with blood
Mechanical events of the cardiac cycle:
- Atrial systole
- Isometric ventricular contraction
- Ventricular ejection
- Isometric ventricular relaxation
- Late diastole
know all the phases in detail!! Write out!!
!!!!!
S1 sound is produced by:
-closure of AV valves and backflow of blood against ventricular walls
*louder sound
S2 sound is produced by:
-Closure of the semilunar valves and recoil of the blood against the atrial wall
S3 sound should NOT be heard, but would be produced by:
Rapid ventricular filling in early diastole
When is the only time you should hear S3 sounds?
In children and pregnant women
S4 sounds should NOT be heard but are due to:
Turbulent flow due to stiff left ventricle/ventricular non-compliance
Abnormal heart sounds are called ___________ and are caused by ___________ blood flow through the heart
Murmurs, turbulent
Where to listen for a systolic murmur?
Aortic area
Where to listen to systolic ejection murmur?
Pulmonic area
Where to listen to holosystolic and diastolic murmur?
Tricuspid area
Where to listen to holosystolic, diastolic, and systolic murmur?
Mitral area
Frank starling mechanism in regulation of heart pumping:
Increases in end-diastolic fiber length produce increases in cardiac output
Sympathetic nervous system on regulation of heart pumping:
Increase heart rate, contractibility, and vascular tone
Parasympathetic nervous system on regulation of heart pumping:
Decreases heart rate and cardiac contractility slightly
