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Cardiac Output (Heart Rate (positive chronotropic factors (exercise,…

- - - - ACH hyperpolarizes pacemaker cells by opening K+ channels, which will slow the HR
      - This will cause a greater difference in membrane potential jumps, which will create the slower HR
  - - - Norepinephrine is released and binds to receptors on the heart, reducing repolarization and making it easier to depolarize quicker
      - This will cause a decreased difference in membrane potential jumps, which will create a faster HR
- - - - definition: cardiac cell contractile force
      - Positive inotropic agents increase contractility
        
        increased sympathetic stimuli
        
        certain hormones (epinephrine, thyroxine, and glucagon)
        
        Ca+2 (required for binding to troponin)
      - Negative inotropic agents decrease contractility
        
        increased extracellular K+
        
        calcium channel blockers
        
        acidosis
    - - definition: back pressure exerted by blood in the large arteries leaving the heart
      - ventricles must overcome to eject blood
      - not a major determinant of SV in normal individuals
      - hypertension ^ after load -> ^ ESV, decreases SV
    - - venous return
        
        definition: amount of blood returning to the heart. The most important factor in preload stretching of cardiac muscle
        
        Slow heartbeat and exercise increase venous return to the heart, increasing SV
        
        Blood loss and extremely rapid heartbeat decrease venous return and SV
        
        ^ venous return -> ^ EDV -> ^ SV -> ^CO
      - definition: amount ventricles are stretched by contained blood. this is the critical factor controlling SV