Cardiovascular physiology

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Cardiovascular physiology
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2013-03-19 12:36:47
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Physiology t2
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Cardiovascular physiology, t2
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  1. Blood vascular system consists of (3, 5)
    • Heart
    • Blood
    • Blood vessels (arteries, arterioles, capillaries, venuoles, veins)
  2. functions of cardiovascular system (3)
    • distribute and collect blood to and from organs and tissues. 
    • Distribution, Regulation, Protection
  3. Blood functions in distribution (4)
    • Supplies oxygen
    • supplies nutrients
    • removes waste and CO2
    • transports hormones
  4. Blood function in regulation (3)
    • Regulates body temperature
    • regulates pH
    • Regulates blood volume to supply efficient circulation to cells, tissues, organs and systems
  5. Blood functions in protection (2)
    • prevents blood loss
    • prevents infection with WBCs, complement and antibodies. 
  6. Placement of heart
    • Dogs and cats ribs 3-7, horses ribs 2-6.  Great vessels in base, apex points caudally, ventrally, a little left. 
    • (left) low P high A low M
    • (right) High A low T
  7. Mediastinum
    area around heart.  Cranial, Middle (contains heart), caudal. 
  8. Which heart vessels have no valves? 
    Pulmonary veins or vena cavae.  Contaction compresses to prevent backflow. 
  9. Sac around heart and layers of heart
    • Pericardium: (out to in) fibrous, parietal serous, visceral serous (same as epicardium)
    • Epicardium
    • Myocardium
    • Endocardium (continuous with tunica interna of great vessels)
  10. What was wrong with Gertrude?  Cow, arched back, grunting, "anxious expression", reluctant to move
    Traumatic pericarditis.  Nail or wire eaten, wanders from reticulum to pierce pericardium.  Inflammation constricts, causing heart failure. 
  11. How do valves work?
    Upon contraction, chordae tendinae becomes firm, papillary muscles contract and cusps are pulled open.  Cannot pull the other way due to chordae tendinae, so one-way blood flow with no everting. 
  12. Higher pressure system in circulatory
    Left system (pumps oxygenated blood from heart into aorta)
  13. Layers of blood vessels
    • Tunica interna (endothelium.  Simple squamous.  Some big vessels have sub-endothelium and basement membrane)
    • Tunica media (smooth muscle controlled by sympathetic nervous system)
    • Tunica externa (fibrous with collagen.  Protect, anchor, hold lymph, nerves, vaso vasorium)
  14. Capillaries only have
    tunica interna
  15. veins or arteries are bigger?
    Lumen of veins is bigger, arteries have bigger walls, more smooth muscle and elastic tissue
  16. who has more elastic tissue and smooth muscle?
    arteries
  17. Who has more endothelium?
    Nobody--arteries, veins and capillaries are the same. 
  18. Who has higher pressure?
    arteries. 
  19. Arteries
    • Biggest vessels that carry oxygenated blood away from heart.  Thicker and more elastic pressure maintains BP near the heart.  Dampen BP changes.  Elastic or conducting.  Torturous.  Smooth muscle and elastic tissue.
    • Low compliance, high recoil
  20. Arterioles
    use resistance (muscle to regulate flow of blood) to make systemic blood pressure.  Many have sphincter for adjustable resistance. 
  21. resistance and where it is greatest
    arterioles use muscle to regulate blood flow, some with a sphincter.
  22. Capillaries
    • smallest vessels going from arteriole to venule.  Only contain tunica intima, RBCs must go single-file, contain tiny pores or clefts to allow exchange.
    • Continuous, Fenestrated or Sinusoid
    • Move with diffusion or bulk flow
    • Not high resistance due to branching. 
  23. Continuous capillaries
    in skin and muscle, uninterrupted, contain tight junctions and tiny pores. 
  24. Fenestrated capillary
    oval pores between endothelial cells in capillaries that increase leakiness.  Found in choroid plexus, ciliary process of eye, endocrine glands, kidney, small intestine. 
  25. Sinusoid capillary
    HUGE fenestrations, large irregular lumens and holes in endothelial cells.  No basement membrane makes them very leaky.  Found in liver, bone marrow, lymphoid tissue, anterior pituitary and parathyroid. 
  26. Capillary diffusion
    • Simple: O2, CO2, glucose, amino acids, hormones
    • Water: diffusion (osmosis), bulk flow (hydrostatic pressure)
    • Filtration (outward flow)
    • Reabsorption (from interstitial to capillaries)
  27. venules
    vary in size, from capillaries to veins
  28. veins
    • distensible, major reservoir vessels (capacitance).  Thinner walls with less elastin and muscle than arteries.  Large lumen, low-pressure system.  70% of blood volume in veins. 
    • Have small valves: one-way folds of interna to prevent backflow, squeezed by skeletal muscle around vein.
  29. Where is blood flow slowest
    capillaries
  30. what part of blood circulation has highest surface area
    capillaries
  31. why does velocity of blood increase after capillaries
    venules and veins have skeletal muscles pushing blood towards heart
  32. vessel diameter is greatest in
    veins, then arteries
  33. cross-sectional area is greatest in
    capillaries
  34. average blood pressure is greatest in
    arteries, arterioles
  35. Velocity of blood flow is greatest in
    arteries/arterioles, then veins.  Lowest in capillaries
  36. Where is most blood when resting
    veins--70%.  Large lumen, thin walls
  37. Where do vena cavae drop blood
    right side of heart
  38. Which circulatory systems work in series
    pulmonary and systemic, alternate. 
  39. Which areas have a portal system and what is it
    • Where blood goes through two capillary beds
    • kidney, liver, brain
  40. which circulatory system is parallel
    systemic.  Sends blood to many areas at the same time, all happen together, parallel
  41. Blood from GI goes first to
    liver, to be filtered before systemic circulation.  Portal system for max filtration/exchange
  42. Hepatic circulation
    • aorta to celiac artery to hepatic artery to liver (capillary bed) to hepatic vein to caudal vena cava to heart. 
    • OR
    • digestive tract arteries to capillary bed to hepatic portal vein to liver (capillary bed) to hepatic vein to caudal vena cava to heart. 
  43. Blood flow
    • volume flowing through a given structure per unit time (mL/min)
    • Blood flow = DP (change in pressure, pressure gradient)/resistance
    • Resistance up, BF down; pressure up, BF up
  44. Blood pressure
    • the pressure that blood exerts across the blood vessel wall
    • force per unit area (mmHg)
    • highest in aorta, lowest in right atrium
  45. Resistance
    opposition to flow: generally encountered in the systemic circuit.  peripheral resistance (PVR)
  46. Mean circulatory filling pressure
    pressure when heart stops.  not zero because of recoil of blood (arteries)
  47. Blood pressure changes through system
    Highest in arteries, slows as friction uses up energy.  How much depends on how much friction or resistance.  Lowest in veins/vena cavae. 
  48. Sources of resistance
    • Blood viscosity: (too many RBCs or dehydration raises viscosity, raises resistance, lowers flow.  Hemorrhage/anemia causes opposite)
    • Total blood vessel length: (longer vessel causes greater resistance)
    • Blood vessel diameter: most important.  Flow is inversly related to diameter (higher lumen size makes less resistance)
  49. adjustable resistance
    sphincter muscle causes contraction or dilation, allowing ateriole to adjust resistance.  Arteriole walls are muscular. 
  50. Unidirectional flow of veins
    • pumping action of skeletal muscle contraction
    • one-way valves
    • respiratory pump
  51. What part of cardiac cycle has highest BP?
    Left ventricular systole (~120)
  52. Recoil
    pushback in arteries caused by thick, strong walls that accepts an increase in pressure and sustains BP during heart distole.  Arteries are elastic.
  53. what part of cardiac cycle has lowest BP
    ventricular distole
  54. Cardiac cycle, starting with late distole
    • AV valves are open, semilunar valves are closed. 
    • Atrial systole.  Blood fills ventricles.  End diastolic volume reached.  Max blood in heart. 
    • Ventricle contracts.  Increase of pressure, blood is pushed back towards atria.  AV valves are closed. 
    • Isovolumic ventricular contraction. 
    • Pressure in ventricles is higher than aorta/pulmonary trunk, semilunar valves are pushed open.  Blood rushes into aorta/pulmonary trunk.  aortic pressure increases, ventricular pressure decreases, ventricle starts to relax. 
    • Ventricular pressure below aorta/pulmonary pressure, blood tries to backflow, semilunar valves close
    • End systolic volume-minimum blood in heart.  All valves closed. 
    • Isovolumic ventrical relaxation. 
    • blood is entering atria through non-gated pulmonary vein/vena cavae.  Pressure in atria greater than pressure in ventricle pushes AV valves open.  Late diastole. 
  55. 2 ways to check BP
    • arterial blood pressure (mmHg)
    • central venous pressure (CVP)(cmH2O)--interthoracic vena cava
    • 1 mmHg = 1.36 cm H2O (not on test)
  56. Pulse
    • wave of pressure that travels through arterial walls when left ventricle ejects blood into aorta. 
    • Clinical indicator of the rate, regularity and strength of heartbeat. 
  57. Where to take pulse in dogs, cats, sheep, goats, horses, large animals
    • dog/cat/sheep/goat: femoral artery  (inguinal)
    • horses: digital or facial arteries
    • large animals: coccygeal artery (tail)
  58. Herat sound one
    close of AV valves.  beginning of systole
  59. Heart Sound 2
    close of semilunar valves.  End of ventricular systole
  60. Ventricular systole
    space between first and second heart sound. 
  61. End diastolic volume (EDV)
    maximum blood in heart, when atria is in systole and ventricle is in diastole.
  62. Isovolumic ventricular contraction
    when all doors to ventricle are closed and max blood is inside (EDV)
  63. End systolic volume (ESV)
    minimum blood in heart, blood left after ventricle contracts in systole. 
  64. Isovolumic ventricular relaxation
    when all doors to ventricle are closed and minimum blood is inside (ESV)
  65. Cardiac output (CO)
    • the quantity of blood pumped by the left ventricle into the aorta EACH MINUTE
    • CO=SV x HR
    • altering stroke volume or heart rate will alter cardiac output
  66. Stroke Volume (SV)
    • the quantity of blood pumped by the left ventricle into the aorta with EACH VENTRICULAR CONTRACTION
    • CO=SV x HR
    • SV = EDV - ESV
    • altering stroke volume will alter cardiac output
  67. Cardiac output equation
    • CO = SV x HR
    • Cardiac output = stroke volume x heart rate
  68. Distribution of cardiac output between resting and exercising animal
    • Brain stays the same, muscles increase, heart increases a little, gut/renal decreases.
    • Determined by resistance, so arterioles dilate or contract
  69. Stroke volume equation
    Stroke volume = end diastolic volume - end systolic volume
  70. Factors that regulate stroke volume by increasing end diastolic volume
    • Preload
    • Compliance
    • Diastolic Filling Time
  71. Preload
    • The initial stretching of the cardiac myocytes prior to contraction (sarcomere length).  More blood in stretches sarcomere.  Less, no stretch. 
    • Measured by Left ventricular end diastolic pressure (LVEDP)
    • changes end diastolic volume and therefore stroke volume and cardiac output
  72. Left Ventricular end diastolic pressure
    • The pressure exerted on the walls of the left ventricle at the end of diastole. 
    • means of measuring sarcomere length in the heart (to measure preload). 
    • Accepted as measurement of preload.
  73. Effects of preload on EDV, SV
    Preload increases, EDV increases, SV increases
  74. Starling's Law of the Heart
    • The more the heart is filled during diastole, the greater the volume of blood is pumped out. 
    • (higher volume of incoming blood stretches the vessels, causing a greater force of contraction)
    • Increased preload or LVEDP=increased EDV = stretched muscle fibers = increased contractility = increased stroke volume = increased Cardiac output
  75. Compliance
    • a measure of the ease with which the ventricular walls stretch to accommodate incoming blood during diastole
    • Increase in compliance = increase in End diastolic volume = increase in stroke volume = increase in cardiac output
  76. diastolic filling time
    • The length of time available for ventricular filling during diastole.  Increase increases end diastolic volume.  (affected by heart rate). 
    • Increase filling time, increase stroke volume
  77. Factors to decrease end systolic volume to increase stroke volume
    • Empty the ventricles more completely during systole:
    • Contractility
    • Afterload
  78. Contractility
    • pumping ability of a ventricle. 
    • Increased empties the ventricle more and decreases end systolic volume, increasing stroke volume without increasing end diastolic volume
  79. Cardiac afterload
    • Sum of all forces opposing ventricular emptying during ventricular systole
    • Dilation of arteries causes an decrease in afterload and an increase in stroke volume
    • Contraction of arteries causes an increase in afterload and a decrease in stroke volume.
    • OPPOSITE
  80. Peripheral vascular resistance (PVR)
    the impedance to blood flow through the systemic arteries caused by constriction of the arterioles.  (determined by arterioles)
  81. Arterial blood pressure equation
    • Arterial BP = CO x PVR
    • Arterial Blood pressure = Cardiac output x Peripheral Vascular Resistance
  82. Normal arterial BP determination and values
    • take 5-6 recordings and average. 
    • Listen to artery, put a cuff on until you can't hear, release pressure, first time you hear is systolic
    • Cat is high if over 160 mmHg
    • Dog is high if over 170-189 mmHg
  83. Syncytia
    interconnected mass of fibers with many nuclei but no separate membranes.  Atria and ventricles function as two separate syncytia separated by a fibrous band
  84. Why do atria and ventricles go into systole and diastole separately?
    Action potential has to go around fibrous band separating syncytia, then through very few gap junctions to give ventricles time to fill. 
  85. Why is the action potential so long in heart muscle? 
    Ca channels instead of Na makes longer depolarization period, then K channels open even more slowly.  This provides a longer absolute refractory period and prevents tetany. 
  86. 2 types of cells in cardiac action potential
    • autorhythmic: do not have resting membrane potential, drift toward threshold on their own (SA node)
    • Nonpacemaker: resting potential, long action potential due to calcium and slow potassium
  87. Where do Ca ions come from to contract the heart? 
    Sarcoplasmic reticulum and extracellular fluid
  88. Digitalis
    drug that helps with heart failure.  Slows down Ca removal from cytosol to increase heart contractions.  Stops sodium potassium pump so Ca won't exit cell. 
  89. Cardiac conduction system
    • generates rhythmic regular action potentials
    • conducts action potentials through myocardium (organized, synchronized) for effective pumping
    • made up of autoarrhythmic cells that can generate own action potential (pacemaker)
    • path for electrical excitation. 
  90. parts of conduction system
    • sinoatrial node
    • atrioventricular node
    • AV bundle or bundle of His
    • Right and left bundle branches
    • Purkinje Fibers
  91. What happens if the SA node doesn't fire?
    The AV node will take over.  If that fails, the Purkinje fibers will fire, but slower.  SA is just the fastest, so the others follow suit
  92. Where is the pause in the conduction system in the heart?
    AV node, where electrical stimulus is going around the fibrous band and squeezing through few gap junctions, giving the ventricles time to fill.  This sets the rhythm. 
  93. Electrocardiogram
    • graphic recording of the electrical currents of the heart, measured on the surface of the body (NOT A MEASURE OF HEART FUNCTION)
    • Major waves: PQRST
    • Uses nodes. 
  94. What Lead do vets use in ECG?
    • Lead II.  Right arm is negative (white)
    • Left leg is positive (Red)
    • Left arm is the ground.  (black)
    • Placed at joints (elbow and stifle)
  95. Depolarization rules
    • Toward the + (left leg) means + (up) (P, R)
    • Away from the + means - (Q, S)
  96. Repolarization rules
    • Opposite of depolarization. 
    • Toward +(Left leg) means - (down)
    • Away from + means + (up) (usu T wave, sometimes not)
  97. P-wave
    atrial depolarization, positive, towards left leg
  98. QRS complex
    • Ventricular depolarization
    • Q, tiny negative (sometimes missing)
    • R, huge positive
    • S, tiny negative
  99. T-wave
    • repolarization of ventricles
    • can be positive (usually) or negative. 
  100. To read ECG
    • Rate, Rhythm, Axis, P wave morphology, PR interval, QRS complex morphology
    • ST segment morphology
    • T wave morphology
    • Use graph boxes.  Can't diagnose just from ECG. 
  101. Relationship between ECG waves and systole/diastole
    • Waves precede/cause contraction. 
    • P before atrial systole
    • QRS before ventricular systole. 
  102. Automaticity
    • The ability to spontaneously initiate a depolarization, triggering an action potential
    • All (autorhythmic) conduction fibers CAN, but only SA node exhibits automaticity
    • SA node is faster, so it sets the heartrate
  103. Who are the latent pacemakers
    AV node and His-Purkinje system.  Would set heart rate if SA failed
  104. Autonomic nerve supply to heart
    • Brain stem (medulla) regulates. 
    • Sympathetic, norepinephrine, stimulate ventricles.  Increase force of contraction. 
    • Parasympathetic, vagus, acetylcholine, can decrease but doesn't affect force of contraction. 
  105. Cardiac arrhythmias (dysrhythmias)
    • deviations from the norm: cardiac rate or rhythm, site of origin of cardiac impulse, sequence of activation of atria and ventricles. 
    • Comes from abnormalities in impulse initiation OR impulse conduction
  106. Sinus bradycardia
    • regular sinus (SA) rhythm that is slow. 
    • Don't treat without seeing lethargy/collapse.  Then give atropine (decrease the parasympathetic)
    • Caused by elevated vagus or decreased sympathetic, hypothermic, hypothyroid, sick sinus syndrome, vagus due to other systemic disease (respiratory, neurologic, ocular, GI, urinary)
  107. Sinus tachycardia
    • regular sinus (SA) rhythm at a fast rate.
    • treat problem not symptoms
    • caused by stress (ups sympathetic), hyperthyroid, fever, hypervolemia, compressed heart (tamponade), heart failure, drugs that increase the SA (catecholamines).
  108. Sinus arrest
    • failure of the SA node to discharge for a short period of time. 
    • Causes pause between complexes of ECG.  Missing beat. 
    • heart rate is interrupted by escape beat or resumption of sinus. 
    • Possible fainting or weakness
  109. Arrhythmia from impulse initiation
    • impulse initiation from abnormal or ectopic impulse (some part of heart not SA node signaling contraction).  Are described by site of origin (atrial, junctional, supraventricular, ventricular)
    • characterized by timing (premature or escape)
  110. tachycardia
    abnormal premature arrhythmias in groups of three or more.
  111. Supraventricular (atrial or junctional) premature complex
    • arrhythmia where early arrhythmia is initiated from above the AV node, either in atrium or AV junction (just above node). 
    • QRS complex normal but premature
    • p wave can be weird. 
    • Not always very obvious
  112. Ventricular premature complex (VPC)
    • depolarization coming from a site within ventricular myocardium. 
    • complex is wide, bizarre and early.  P wave not associated
  113. ventricular tachycardia
    three or more ventricular premature depolarizations conseculatively
  114. atrioventricular (AV) block
    • alteration of impulse conduction from atria to ventricles.  Something is stopping/slowing
    • Three degrees of AV block
  115. First degree AV block
    • Something is slowing electrical impulse from atria to ventricles. 
    • Conduction time is increased. 
    • Increased inerval between P and R on ECG
  116. Second degree AV block
    • intermittent conduction.  Occasional impulses fail to make it from atria to ventricles.  Atrial contraction is not followed by ventricular contraction. 
    • May be at regular intervals or random
    • 2 types (Type 1 and type 2)
  117. Second degree AV block type 1
    • Intermittant conduction between atria and ventricles. 
    • Increasing delays in each cycle of ECG before an omission. 
    • Pattern. 
  118. Second degree AV block type 2
    • Intermittant conduction between atria and ventricles. 
    • No pattern.  Random. 
  119. Third degree AV block
    • Complete heart block.  No impulses are conducted from atria to ventricles. 
    • Lack of synchronization between P-wave and QRS complex. 
  120. What was wrong with Molly?  11yr spayed whippet.  Respiratory distress, thick white mucous, choking cough, tired, losing weight, abnormal lung sounds, left systolic murmur
    Degenerative mitral disease or mitral regurgitation.  Mitral valve is thickened and no longer closing properly, so blood is flowing backward.  Left heart failure.  Pulmonary edema.  Management (treat respiratory signs). 

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