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ch. 12 heart (14 steps of blood flow (Lungs, Pulmonary Veins, Pulmonary…

- - - - = outermost, tough, fibrous protective layer
    - - visceral pericardium= innermost delicate epithelial
      - Parietal pericardium= inner linning of fibrous pericardium
  - - - atria are thin walled chambers
      - atria recieve blood from veins
      - ear like flaps called auricles cover the atria
    - - ventricles pump blood from the heart into arteries
      - thick walled chambers
      - right and left ventricle are seperated by the interventricular septum
      - trabeculae carnae is the irregular inner surface of the ventricles
    - - bicuspid valve lies between the left atrium and ventricle
      - chordae tendinae= tendon like fibrous cords that connect the cusps of AV valves to the papillary muscle of ventricles
        
        prevent cusps from swinging back to the atria
      - tricuspid valve lies between the right atrium and ventricle
      - Papillary muscle= the muscular columns that are located on the inner surface of the ventricles
    - - the pulmonary SL valve lies within the pulmonary trunk
      - the aortic SL valve lies within the aorta
  - - - coronary arteries carry blood to the myocardium
      - pulmonary arteries carry blood from the right ventricle to the lungs
      - aorta carries blood from the left ventricle to the body
      - carry blood that is high in O2, and low in CO2, except pulmonary arteries that are low in O2, and high n CO2
    - - carry blood that is high in CO2 and low in O2 except pulmonary veins that are high in O2 and low in CO2
- - - - contractile fibers of the heart have a resting potential of -90mV
      - when the potential is brought to -70mV by excitation of neighboring fibers, certain sodium channels open very rapidly
      - Na+ ions rush into the cytosol of fibers and produce a rapid depolarization
    - - Ca++ binds troponin....contraction
      - Depolarization is maintained for 0.25 seconds
      - Ca++ ions pour out of SR into sytosol
      - Ca++ ions enter cytosol of fibers from ECF
      - Ca++ channels open
    - - K+ ions diffuse out of fibers
      - Na+ and Ca+ channels close
      - K+ channels open
      - -90mV resting potential is restored
    - - longer contraction itself
      - neccessary for ventricles to relax and fill with blood before again contracting to eject the blood
    - - caused because cardiac muscle is at less than optimal length when the heart is at resting rate
      - the frank-starling law of the heart says thar strength increases
      - within physiological limits increased stretch of cardiac muscle fiber will increase the strength of contraction
      - Basically this means that as blood flows into the heart it must be pumped out
  - - - atrioventricular bundle
        
        only electrical connection between the atrial and the ventricles
        
        located in the superior interventricular septum
        
        impulse enters both right and left bundle branches
      - atrioventricular node
        
        located in interatrial septum
        
        serves as a delay signal that allows for ventricular filling
        
        cardiac impulse enters the atrioventricular bundle
      - right and left bundle branches
        
        lead downward through interventricular septum toward the apex and impulse finally reaches the purkinje fibers
      - sinoatrial node
        
        pacemaker=self exciting tissue indicates cardiac impulses
        
        impulse travels throughout atrial fibers via gap junctions in intercalated discs to the atrioventricular node
        
        located in right uppermost atrial wall
      - purkinje fibers
        
        located within the papillary muscles of the ventricles
        
        conduct the impulse into the mass of ventricular muscle ftissue
        
        large diameter conduction myofibers
        
        cause ventricles to contract which forces blood put
  - - - the conduction pathway is normal
      - the heart is enlarged
      - certain regions are damaged
    - - depolarization procedes contraction
      - repolarization precedes relaxation
    - - QRS complex
        
        begins as a downward deflection,continues as large, upright, triangular wave, ends as a downward wave
        
        represents onset of ventricular depolarization
        
        shortly after QRS begins, ventricles start to contract
      - T wave
        
        dome shaped, upward deflection
        
        represents ventricular repolarization
        
        occurs just before ventricles start to relax
        
        shape indicates slow process
        
        P-Q interval and S-T segment
      - P wave
        
        represents atrial depolarization
        
        0.1 sec after p wave begins, atrial contracts
    - - enlarged Q wave= MI
      - enlarged R wave= ventricular hypertrophy
      - enlarged P=enlargement of an atrium possibly due to mitral stenosis
- - - - blood flows from areas of high pressure to areas of low pressure. As a chamber of the heart contracts, pressure increases, while as a chamber relaxes, pressure decreases
      - the atria and ventricles alternately contract and relax
      - definitions
        
        systole=phase of contraction
        
        diastole=phase of relaxation
      - a complete cardiac cycle includes systole and diastole of both atria and systole and diastole of both ventricles
      - includes all of the events associated with one heartbeat
    - - relaxation period
        
        ventricular pressure drops
        
        SL valves close
        
        isovolumetric relaxation for brief time
        
        when ventricular pressure drops below atrial pressure, AV valves open
        
        0.4 seconds
        
        follows T-wave
    - - rapid ventricular filling occurs just after AV valves open
    - - ventricles have completed filling=end-diastolic volume
      - atria relax, ventricles depolarize
      - SA node fires, atria contract, and remainder of ventricular filling occurs
      - 0.1 seconds
    - - ventricular pressure increases rapidly
      - AV valve close
        
        End-systole volume reached when ventricle finish emptying 0.3 seconds
        
        ventricular ejection phase= opening of SL valves to closing of SL valves
        
        isovolumetric contraction phase= start of contraction to opening of SL valves=0.05 sec
        
        stroke volume= end-diastole volume minus end-systole volume
      - ventricles contract
      - impulse passes through AV node and then through ventricles
  - - - lubb=closing of AV valves
      - dubb=closing of SL valves
    - - these sounds can be heard through a physician's stethoscope. They represent the closing of heart valves, and therefore help in diagnosing any problems occurring in the valves.
    - - if the closing of the valve cusps is incomplete some blood may leak back=murmur