Physio Cardio Intro/Mechanism (11/12)

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Physio Cardio Intro/Mechanism (11/12)
2014-02-05 19:43:39
MBS Physiology
Exam 2
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  1. Lecture 11 - Cardio Intro
  2. Path of Blood Through the Heart
    • deoxygenated blood from the systemic circulation enters the Right Atrium through the Superior Vena Cava & the Inferior Vena Cava
    • once in the Right Atrium, blood flows through the Tricuspid Valve into the Right Ventricle
    • from the Right Ventricle blood is pumped through the Pulmonary Semilunar Valve, enters the pulmonary artery & is taken to the lungs
    • oxygenated blood from the lungs flows through the pulmonary vein into the Left Atrium
    • it's then pumped through the Mitral Valve into the Left Ventricle
    • from the Left Ventricle it's pumped through the Aortic Semilunar Valve to the aorta & enters the systemic circulation
  3. Tricuspid Valve
    • separates the Right Atrium & the Right Ventricle
    • prevents back-flow of blood back into the Right Atrium
    • opens during diastole so blood can empty from the Right Atrium into the Right Ventricle
  4. Pulmonary Semilunar Valve
    • lies between the Right Ventricle & the pulmonary artery
    • opens in ventricular systole when the pressure in the Right Ventricle rises above the pressure in the pulmonary artery
  5. Mitral Valve
    • separates the Left Atrium & the Left Ventricle
    • opens during diastole
    • open during diastole
  6. Aortic Semilunar Valve
    • separates the Left Ventricle & the aorta
    • opens in ventricular systole when the pressure in the Left Ventricle rises above the pressure in the aorta
  7. Stenosis
    • when the tissues forming the valve leaflets become stiffer, narrowing the valve opening & reducing the amount of blood that can flow through it
    • main cause: arteriosclerosis
    • result: the body may not receive adequate blood flow
  8. Organization of Cardiac Muscle
    • cardiac muscle layers are oriented differently in comparison to each other
    • innermost layer = longitudinal
    • middle layer = circular
    • 2 outside layers = oblique
    • important so that the atria & ventricles can pump all blood they come in contact with into where they need to go
  9. How does the pressure in the Left Ventricle compare to the pressure in the Right Ventricle?
    • L: 120/0 mm Hg
    • R: 25/0 mm Hg
    • the left ventricle needs to pump blood throughout the entire systemic circulation which the right ventricle need only pump it through the pulmonary system
    • even though the SAME amount of blood is pumped through systemic & pulmonary systems, the pressure generated is difficult due to the fact that the L ventricle experiences more RESISTANCE to flow than the R
  10. Cardiac Output (CO)
    • the TOTAL volume of blood flow through the systemic or pulmonary circulation
    • units = mL/min
    • CO = heart rate X stroke volume
    • typically 5L/min
  11. What are the two parameters that determine cardiac output?
    • 1. heart rate
    • 2. stroke volume: volume of blood ejected from a ventricle (~70 cc)
  12. Flow (Q)
    • volume/time; cm3 of blood per minute
    • a snapshot of blood moving
    • is kept in one direction by the presence of valves, between atria & ventricles (tricuspid & mitral) & between ventricles & pulmonary artery or aorta (pulmonic & aortic valves)
  13. Velocity (V)
    • distance blood moves/time; cm/min
    • V (cm/min) = flow (Q) (cm3/min) / X-Sectional Area (cm2)
    • how far a RBC moves per some time frame (can measure using doppler principle)
  14. Will a certain volume of blood move faster through a vessel with a large cross sectional area or a small cross sectional area?
    • a certain volume of blood flow will have a HIGHER velocity going through a vessel with a small cross sectional area than it will going through a vessel with a large cross sectional area
  15. How is cardiac output minus coronary flow measured?
    • using an ultrasonic doppler flow meter
    • it's placed over the ascending aorta & measures both its cross sectional area & the velocity of flow through the vessel
    • Q (cm3/min) = V (cm/min) * A (cm2)
    • Q = VA
  16. How does the velocity of blood change through the vascular system?
    • the flow always stays constant - it's determined by cardiac output, however blood velocity changes
    • the aorta is branching into smaller vessels & the overall cross sectional area is INCREASING (capillary x-sectional A = > 40,000 cm2)
  17. Blood Velocity
    • fastest
    • Aorta = Arteries
    • Vena Cava (~same as arterioles)
    • Arterioles (large variation)
    • Veins
    • Venules
    • Capillaries
    • slowest
  18. Why is blood velocity slowest in the capillaries?
    • because that's where exchange of nutrients, O2, & CO2 is happening - blood wants to move SLOWLY here to allow for thorough exchange to occur
    • the entire point of the cardiovascular system is to get blood to the capillaries
  19. Relationship Between Pressure & Flow
    • QR = P1 - P2
    • (Flow)(Resistance) = Mean Pressure
  20. Mean Arterial Pressure (MAP)
    • (SYSP - DIASP)/3 + DIASP
    • 1/3(S - D) + D
    • an average blood pressure in an individual; the average arterial pressure during a single cardiac cycle
  21. Poiseuille’s Law
    • defines the effects of fluid viscosity, tube radius, & length on the relationship between pressure drop & flow
    • Q = ΔPπr4/8ηL
    • ΔP = Q * { 8ηL/πr4 } {} = resistance
    • ΔP = QR, Q = ΔP/R
  22. In Poiseuille’s Law why is the blood vessel radius raised to the 4th power?
    • because blood vessel walls can stretch - their radius can change
    • has a profound effect on resistance
    • constricting & dilating BVs is one of the main ways vessels direct blood flow throughout the body
  23. η (Eta)
    • difficulty of blood to flow over other blood (viscosity)
    • stays the same unless a person becomes very sick
  24. Lecture 12 - Mechanical Events of the Cardiac Cycle
  25. How are pressures in blood vessels & cardiac chambers measured?
    via saline filled catheters of 2 basic types attached to electronic pressure transducers
  26. How are volumes of cardiac chambers measured?
    • using echo-cardiographic imaging techniques or calculated from flow measurements
    • echocardiography looks at chamber volume & how much blood they hold
  27. Cardiac Catheterization
    • used to study the mechanical events of the cardiac cycle
    • inserted into artery or vein & passed into chambers of the heart
    • attached to electronic pressure transducers to measure pressure
    • blood can be withdrawn through the catheters to obtain blood gas measurements
  28. Swan-Ganz catheter
    • used to catheterize the chambers & vessels of the right side of the heart
    • measure pressures in the right side of the heart, pulmonary arteries, veins, & left atrium
    • can be inserted into a (neck) vein & pushed forward to a position where the tip is at the junction of the vena cava & the right atrium
    • here the catheter is swept along w/ venous return into the right atrium
  29. What pressure can be measured when Swan-Ganz catheter is carried into a small pulmonary artery & then “wedges” there?
    • the “pulmonary wedge pressure”
    • this is a good indicator of left atrial pressure, which otherwise can't be measured by a catheter
    • records the back pressure pushing against the catheter coming from the L atrium
  30. Left Heart Catheterization
    • measures aortic pressure & L ventricular pressure
    • the catheter must be inserted into a peripheral artery (femoral) & advanced against the direction of arterial blood flow
    • it approaches the left ventricle is from the aorta
    • used to get left ventricular pressure (NOT arterial)
  31. How can mitral stenosis be assessed?
    by examining the pressure gradient between the “pulmonary wedge” pressure & the ventricular pressure during diastole (when the mitral valve is open)
  32. Both ventricular & atrial ________ happen simultaneously, while there is a slight time difference between atrial _______ & ventricular _______.
    • ventricular & atrial DIASTOLE happen simultaneously
    • there is a time difference between atrial systole, which happens first, followed by ventricular systole
    • atrial contraction is complete before the ventricle begins to contract
    good website*
  34. Atrial Systole
    • when both L & R atria CONTRACT to push blood through mitral & tricuspid valves → this is the "topping off" of ventricles
    • mitral & tricuspid valves are open facing ventricles nearly completely full of blood
    • atrial systole is the final part of diastole (filling)
    • causes an increase in endiastolic (ventricle) pressure
  35. Describe the behavior of the mitral & tricuspid valve during Atrial Systole:
    • in the beginning it's open & has been since rapid ventricular filling during ventricular diastole
    • at the end the mitral valve CLOSES
  36. "a" wave
    occurs when the atrium contracts, increasing atrial pressure, during atrial systole
  37. Atrial Fibrillation
    • NO atrial systole - ventricle don't get "topped off" but because the ventricle is mostly full, enough blood is pumped out to the systemic circulation
    • causes a ~5-10% reduction in normal cardiac output
  38. Ventricular Systole
    • both semilunar valves are open (aortic & pulmonary)
    • the mitral & tricuspid valves are closed
    • both ventricles CONTRACT to push blood through the semilunar valves
    • includes Isovolumetric contraction, Rapid ejection, & Reduced Ejection
    • (mitral valve closure tells you it starts, aortic valve closure tells you its over)
  39. S1
    • signifies the beginning of Systo1e
    • corresponds to closing of mitral (& tricuspid) valve
    • noise made is actually caused by the eversion of the mitral valve slightly back into the left atria due to the large force generated by the L ventricle contracting
  40. What does the QRS complex seen on an EKG indicate?
    it triggers the start of ventricular contraction (systole)
  41. Isovolumetric Contraction
    • the ventricles contract, causing ventricular pressure to rise sharply, but there is no overall volume change b/c atrioventricular valves have just been shut (after atrial systole) & semilunar valves have not yet opened
    • the 1st, short lived part of ventricular systole
    • the beginning corresponds to the R peak seen on an EKG
  42. Describe the behavior of the aortic & pulmonary valve during Isovolumetric contraction (aka the beginning of ventricular systole):
    • both are closed at the start
    • both open at the end of isovolumetric contraction
  43. Rapid Ejection
    • the semilunar (aortic & pulmonary) valves open at the beginning of this phase of ventricular systole
    • ventricles continue contracting, the pressure in the ventricles exceeds pressure in the aorta & pulmonary arteries
    • the semilunar valves open & blood exits the ventricles → causing the volume in the ventricles to decrease rapidly
    • as more blood enters the arteries, pressure there builds until the flow of blood reaches a peak
  44. "c" wave
    • a small wave created by right ventricular contraction which pushes the tricuspid valve into the atrium & increases atrial pressure
    • is normally simultaneous with the carotid pulse
    • visible right between isovolumetric contraction & rapid ejection
  45. Reduced Ejection
    • after the peak in ventricular & arterial pressures, blood flow out of the ventricles decreases & ventricular volume slowly decreases
    • when the pressure in the ventricles falls below the pressure in the arteries, blood in the arteries begins to flow back toward the ventricles & causes the aortic & pulmonary valves to close, marking the end of ventricular systole
  46. Ventricular Diastole
    • mitral (bicuspid) valve open - into left ventricle
    • tricuspid valve open - into right ventricle
    • the ventricles fill during diastole (atrial pressure > ventricle pressure)
    • includes Isovolumetric relaxation, Rapid ventricular filling, Reduced ventricular filling, & Atrial systole
  47. S2
    • the beginning of ventricular diastole
    • corresponds to closing of pulmonary & aortic valve
    • is normally split b/c the aortic valve closes slightly before the pulmonary valve
  48. Isovolumetric relaxation
    • the beginning of diastole during which the atrioventricular valves are still closed
    • throughout this & the previous two phases (rapid & reduced ejection) the atrium in diastole was filling w/ blood on top of the closed AV valves, causing atrial pressure to rise gradually
    • the pressure in the ventricles continues to fall
  49. During which phase is ventricular volume lowest/at a MINIMUM?
    • in isovolumetric relaxation during ventricular diastole
    • at this point the ventricles are ready to be filled again w/ blood
  50. "v" wave
    a slow rise in atrial pressure due to the back flow of blood after it hits the closed AV valves
  51. Rapid Ventricular Filling
    the AV valves open & blood that has accumulated in the atria flows rapidly into the ventricles causing a swift increase in ventricular volume
  52. Reduced Ventricular Filling
    • ventricular volume increases more slowly now
    • the ventricles continue to fill with blood until they are nearly full
  53. End Diastolic Volume (EDV)
    • the volume of blood in the right & left ventricle at end diastole (when it's been almost completely filled)
    • ~50% of it is ejected into the systemic or pulmonary circulation w/ each beat
  54. End Systolic Volume (ESV)
    • the volume of blood in a ventricle at the end of systole (contraction) or the beginning of diastole (filling)
    • is the lowest volume of blood in the ventricle at any point in the cardiac cycle - NEVER 0
  55. EDV - ESV = ?
    • stroke volume
    • amount of blood pumped in each cardiac cycle
  56. Systolic Murmur
    • mitral valve insufficiency (regurgitation, prolapse)
    • aortic stenosis
    • the direction of blood flow is out of the chamber
  57. Diastolic Murmur
    • mitral stenosis: softer murmur
    • aortic insufficiency (regurgitation): more pronounced
    • is softer b/c pressure behind them is lower

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