Cardiovascular Physiology Objectives Objectives Cardiovascular

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Cardiovascular Physiology Objectives Objectives Cardiovascular Powered By Docstoc

                                                 • Review the basic anatomy and
             Cardiovascular Physiology             physiology of the cardiovascular
                                                 • Describe the electrical and mechanical
                  Gems of Wisdom                   events involved in the cardiac cycle.


• Discuss the factors that alter or impact the
  electrical and mechanical events of the
  cardiac cycle.
• Explain the physiology of circulation and       Cardiovascular System Review
  perfusion, including the following
   •   Cardiac output
   •   Blood pressure
   •   Feedback loops
   •   Capillary sphincters

                                                     Anatomy Review

                                                 • Right atrium
          Review of Cardiovascular                 • Incoming blood supply
                                                 • Tricuspid valve
          Anatomy and Physiology:                  • Chordae tendinae and
                 The Heart                           papillary muscles
                                                 • Right Ventricle
                                                   • Pulmonary artery

       Anatomy Review                                            Anatomy Review

  • Left atrium                                              • Heart wall
     • Receives supply                                          • Endocardium
       from the pulmonary                                       • Myocardium
       vein                                                     • Epicardium
  • Left ventricle                                                • Splits into another
                                                                    outside layer – the
  • Bicuspid valve                                                  pericardium
     • Also known as the
       mitral valve
  • Aorta

                                                                                                        Valves of
                                                           Pulmonic                                     the Heart
       The Pericardium                                     Valve

• Fixates the heart to the
  thoracic cavity                                          Aortic Valve
• Relatively inflexible tissue
• Holds 30-50mL of serous
  fluid between the
  pericardium and                                          Mitral Valve
   • Pericardial sac
   • Prevents friction during
     contraction                                           Tricuspid

       Coronary Artery Supplies                                  Coronary Artery Supplies

                                 • Right C.A.                                             • Left C.A.
                                   • Right atrium and                                       • Left atrium
                                                                                            • Nearly all of the
                                   • Inferior portion of                                      left ventricle
                                     the left ventricle
                                   • Interventricular                                       • AV node in half
                                     septum                                                   of the population
                                   • Conduction

                                                                             Physiology of the Heart
          Review of Cardiovascular                                             Electrical components
                Physiology                                                        Electrophysiology
                                                                                 The Cardiac Cycle
                                                                       Mechanical Events of the Cardiac Cycle
                                                                       Influences of Electrical and Mechanical
                                                                                   Heart Function

    Electrical Conduction System                                       Cardiac Cell Types

                                                                   • Electrical cells         • Muscle (myocardial)
                                                                      • Generate and            cells
                                                                        conduct impulses        • Main function is
                                                                        rapidly                   contraction
                                                                         • SA and AV nodes         • Atrial muscle
                                                                                                   • Ventricular muscle
                                                                         • Nodal pathways
                                                                         • Interventricular
                                                                                                • Able to conduct
                                                                           septum                 electrical impulses
                                                                                                   • May generate its own
                                                                      • No contractile               impulses with certain
                                                                        properties                   types of stimuli

    Unique Properties of Cardiac Cells
                                                                         Electrophysiology of the Heart
• Automaticity                   • Conductivity
   • SA and AV nodes                • All cells
                                    • Points of stimulation
                                        • Nervous system
• Excitability                          • Electrolytes
   • All cells                      • Slowing of conductivity
   • Points of stimulation              • Ischemia
      •   Nervous system                • Calcification of nodal
      •   Physical cell damage            pathways
      •   Ischemia               • Contraction
      •   Electrolytes              • Muscle cells

       Review of nerve
                                                                           Nerve impulse Terminology
• Path of travel                                                       • Resting state
  • Stimulation of the nerve             Travel of
                                                                          • The relative electrical charges found on
  • Travel of stimulus down the
                                                        Axon                each side of the membrane at rest
     • “Wave effect” of stimulus down                                        • Net positive charge on the outside
       the axon is caused by the rapid
       movement of ions across the                                           • Net negative charge on the inside
       cell membrane of the axon
                                                                       • Action Potential
  • Impulse moves across
    synapse to another nerve or                                           • Change in the electrical charge caused by
    to a target organ                                Target organ           stimulation of a neuron

                                                                           Action Potential – Resting
       Action Potential Terms
  • Depolarization
     • The sudden reversal of electrical charges
       across the neuron membrane, causing the
       transmission of an impulse
        • Minimum voltage must be met in order to do
          this                                                         • Sodium stays outside of the cell
  • Repolarization                                                        • The pores in the membrane are too small for them to
                                                                            pass through
     • Return of electrical charges to their original
       resting state                                                   • Potassium mostly stays inside
                                                                       • Massively negative charges never leave the cell

         Action Potential - Depolarization
                                                                           Action Potential - Repolarization

• The stimulus hits                                                 • Sodium channels close
  the cell                                                          • Potassium channels
• Sodium channels                                                     open
  open up and                                                         • Potassium pours out
  sodium pours in                                                     • Allows for a quick return
                                                                        to a resting state
• The charges
                                                                    • Sodium is kicked out of
  reverse                                                             the cell
  • Positive inside                                                   • Active transport
  • Negative outside                                                  • Sodium-potassium

       The Action Potential in                                                    The Action Potential in Cardiac
       Skeletal Muscle                                                            Muscle: Step 1
• The electrical events                                                    • The conduction cells
  occurring at the cell                                                      stimulate the                         1
  will always preclude                                                       myocardial cells
  the actual muscle                                                        • Similar events of
  contraction                                                                depolarization
• The action potential is                                                     • Sodium dumps inward
  quick to allow for a                                                        • Potassium rushes out
  faster contraction of                                                       • Sharp spike of the initial
  the muscle                                                                    action potential

       The Action Potential in Cardiac                                            The Action Potential in Cardiac
       Muscle: Step 2                                                             Muscle: Step 3
• The sodium channels close                                                • The calcium channels close
• Calcium channels open                                                      up
  slowly                                                                   • Potassium channels widen                  3
   • Calcium trickles into the cell                                           • Rush of potassium back into
   • Allows for a stronger                                                      the cell
     contraction                                                              • Slower return to a complete
   • Allows all of the ventricular                                              resting state
     cells to contract together                                                  • Allows for contraction to
                                                                                   finish and to get the
• Potassium movement is                                                            ventricular chambers to start
  minimal                                                                          filling with blood

          Action Potential Term:                                                  Electrical and Mechanical
          Refractory Period                                                       Connections
                                      • Absolute                                         Peak of ventricular
                                         • A period of time where the                       contraction
                                           action potential is resistant
                                           to any additional stimuli
                                             • Steps 1, 2 and the early
                                               part of step 3
                                      • Relative
                                         • A period of time where the
                                           action potential moderately
                                           resists a stimulus
                                         • Highlighted area

                                                              The Cardiac Cycle

                                                         • 2 components
                                                            • Diastole
            Mechanical Function                                 • Filling of the chamber
               of the Heart                                 • Systole
                                                                • Contraction of the chamber and ejection of

     Cardiac Output                                                         CO = SV x HR
                                                                   Determination of Stroke Volume
• The amount of blood ejected from the                 • Preload
                                                          • Amount of blood delivered to the chamber
  ventricle in one minute                                 • Depend upon venous return to the heart
• Elements of cardiac output                              • Also dependent upon the amount of blood delivered to
   • Stroke volume       CO = SV x HR                       the ventricle by the atrium
                                                       • Contractility
     • Amount of blood ejected from the ventricle in
       one contraction                                    • The efficiency and strength of contraction
                                                          • Frank Starling’s Law
  • Heart rate
                                                       • Afterload
     • The # of cardiac cycles in one minute
                                                          • Resistance to forward blood flow by the vessel walls

     Another way to look at cardiac
                                                                         Factors Affecting
                                                                         the Cardiac Cycle


    Cardiac Feedback Loops                                         Autonomic Nervous System

• Master controller: the medulla                              • Sympathetic Nervous System
                                                                • Extensively innervates the SA node and ventricular
  • Incoming input                                                cells
      • Chemoreceptors                                             • Increase in heart rate
          • Sense changes in pH, PaCO2 and PaO2                    • Increase in conduction and contractility in the
      • Baroreceptors                                                ventricles
          • Sense changes in arterial pressure                • Parasympathetic Nervous System
  • Response of the medulla                                     • Innervates the SA and AV nodes
      • Stimulate the autonomic nervous system                      • Decreases heart rate
                                                                    • Decreases conduction times through the AV node

    Chemical Factors                                               Chemical Factors

• Hormones                                                     • Electrolyte Concentrations
  • Epinephrine                                                  • Calcium
      • Stimulation of beta receptors in the                        • Impacts the strength of contractions
        myocardium                                                  • High calcium may cause irritability of electrical
      • Increase in contractility of the ventricles                   cells
      • Increase in conduction throughout the

    Chemical Factors                                               The pieces will fit together
• Potassium                                                        soon…
  • Impacts the rates of firing and recovery of the
    cardiac cells
  • High potassium
     • Irregular firing of cardiac cells
     • Dysrhythmias and ventricular fibrillation potentials
  • Low potassium
     • Longer delays in the firing of cardiac cells
     • May be caused by diuretic use
         • Bradycardia
         • Hypotension (systemic complication)
         • Poor cardiac output results


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