2.3 Cardiac Regulation

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  1. 2 phases in cardiac cycle regualtion

  2. 2 things that happens in Systole?
    -heart muscle contraction

    -creates high pressure in chamber
  3. 2 events in diastole
    -heart muscle relaxes

    -drops pressure in chamber
  4. Blood flows through chambers and to great vessels in direction of
    High to low pressure
  5. Cardiac cycle regulation ) Phase 1: ventricular filling (4)
    -pressure in the heart is low

    • -blood returning from circulation is flowing passively thru the atria and into ventricles because AV valves are open but SL are closed.
    • *80% will be delivered to ventricles this way, the rest will be contracted

    -depolarization occurs & atria contracts compressing the residual blood left.

    • -causes slight increase in pressure thus pushing rest of blood into ventricles
    • *ventricles are at last part of their diastole. When atrial relaxes, then ventricles contract (Systole)
  6. Cardiac cycle regulation ) Phase 2 : ventricular Systole & atrial diastole part I (2)
    -as atria relaxes, ventricles start to contract

    -walls close in on blood in chamber to prompting pressure to increase rapidly which closes AV valves
  7. Cardiac cycle regulation ) phase 2 ventricular Systole & atrial diastole: Isovolumetric contraction phase (2)
    -split second period when ventricles are completely closed (AV and SL closed)

    • -Blood volume remains constant as ventricles began to contract
    • *no blood coming in or out
  8. Cardiac cycle regulation ) phase 2 ventricular Systole & atrial diastole: PArt II
    -ventricular pressure rises till it finally exceeds the pressure in large arteries prompting SL to open and eject blood into the vessels
  9. Cardiac cycle regulation ) phase 3 : isovokumetric relaxation (3)
    -following t-wave, ventricles relax

    -blood remaining in chambers are not compressed therefore decrease in pressure within chambers

    -ventricles are closed chambers once again but this time without pressure
  10. All throughout ventricular Systole, (2)
    -atria has been in diastole filling with blood & increasing pressure within but they have AV valves shut.

    -when pressure on atrial side exceeds ventricular side, AV valves pushed open and ventricular filling begins again (phase 1)
  11. Blood enters chambers when pressure of the chamber is _____. Leaves when it is ______
  12. Pressure differentials: which side of atrial builds more pressure?
    Left side
  13. Pressure differentials: why is right atrial pressure lower than left?
    We are trying to get blood from vena cava into RA so it has to be low enough so that vena cava can overcome the pressure
  14. Pressure differentials: which ventricle has higher pressure and why?
    Left because it has to overcome the pressure of pumping blood into the great Aorta to pump it all over the body
  15. How do we derive with pulse pressure?
    Systolic-systolic pressure
  16. Heart sounds) Lub
    - closure of AV valves
  17. Heart sounds) Dub
    Closure of semi-lunar valves
  18. Cardiac output) definition
    • Amount of blood pumped out per minute in each ventricle
    • *whatever comes out must come in to keep mass balance
  19. Cardiac output) formuka
    Heart rate x stroke volume = CO
  20. Cardiac output) Stroke volume , definition
    Volume of blood pumped out by ventricles with each beat
  21. Cardiac output) stroke volume,  formula
    End distaloic volume- end systolic volume
  22. Cardiac output) stroke volume: preload
  23. Cardiac output) stroke volume: 3 most important factors that affect Stroke volume


  24. Cardiac output) stroke volume: what is preload?
    The degree to which cardiac muscle cells are stretched just before they contract (end of diastolic volume)
  25. Cardiac output) stroke volume, preload: venous return, Muscle pump ex
    When walking muscles utilized will pump blood towards heart. So if they're lying around blood tends to pool & not got o heart as quickly as possible
  26. Cardiac output) stroke volume, preload: venous return, Respiratory pump
    Is negative pressure that occurs when inhaling b/c it expands chest & creates negative pressure in chest and helps bring blood in
  27. Cardiac output) starling's law, Main idea (2)
    -more stretch more recoil

    • -at rest cardiac cells are not at optimal length for cross bridges. So the more they stretch the more they get closer to optimal length for strong contraction
    • **the more blood in heart, the more it stretches, the stronger contraction
  28. Cardiac output) contractility : it is independent of (2)
    Blood volume & muscle stretch
  29. Cardiac output) contractility : what dictates contractile strength ?
    Amount of calcium in sarcomere
  30. Cardiac output) contractility : positive inotropism
    • Increases contractility
    • *increases the amount of calcium in sarcomere
  31. Cardiac output) contractility : positive inotropism, sympathetic nervous system
    Increases calcium influx into heart muscle which increases contractility
  32. Cardiac output) contractility : negative inotropism
    Decreases contractility thus reducing calcium influx in cell
  33. Cardiac output) contractility : negative inotropism, parasympathetic n.s
    • Probably decreases calcium influx thus decreasing contracitlity
    • *minimal effect though
  34. Cardiac output) after load: definition
    Amount of pressure from great vessels that the heart must overcome in order to get blood out into the vessels
  35. Cardiac output) after load: hypertension
    Increases amount of force heart must pump against to force blood out since pressure in aorta is higher than normal so heart needs to work harder
  36. Heart rate) what is chronotropic regulation
    Regulation of heart rate
  37. Heart rate) ANS, sympathetic
    • Increases heart rate because it helps pacemaker cells to depolarize quicker thus increasing H.R
    • *Norepinephrine binds to beta adrenergic receptors to cause this
  38. Heart rate) parasympathetic (2)
    • -vagal tone
    • *take away vaagus nerve, heart rate goes up significantly

    -increases K permeability which leads to hyperpolarize cell so decreases heart rate
  39. pressoreceptors
    Input from external sensors in walls or arteries helps regulate heart rate
  40. pressoreceptors: Baroreceptors
    Nerve endings in arterial or cardiac muscle walls that respond to good pressure changes
  41. pressoreceptors: Bainbridge reflex, atrial sympathetic reflex
    Atrial wall stretched -> heart rate increases -> force of contraction increases
  42. Imbalances) congestive heart failure
    Pumping efficiency of heart is so low that blood circulation is inadequate to meet tissue needs
  43. Imbalances) coronary atherosclerosis
    Deposits of yellow plaque from cholesterol build up in blood vessels and impair delivery and flow of blood
  44. Imbalances) hypertension
    Increase in diastolic aorta pressure to above 90
  45. Imbalances) ischemia/angina
    ischemia is decreased of O2 to cardiac muscles thus angina results from lack of O2 or blood being delivered
  46. Imbalances) myocardial infarction
    Heart attack which results of lack of blood therefore lack of O2
  47. Imbalances) cardiomyopathy
    Heart is stretched with poor contractility
  48. Imbalances) pulmonary congestion
    Left ventricle fails so can't pump out blood so blood coming from lungs gets congested bc it cannot go to left side of heart bc its backed up
  49. Imbalances) peripheral congestion
    Right side fails thus its peripheral congestion bc blood cannot get into the RA so its congested in peripherals
Card Set
2.3 Cardiac Regulation
Cardiac cycle regulation
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