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Cardiac Output (Contributing factors (Heart Rate (Influences (Persistant…

- - - - Age: HR slows with age. Fetal HR is between 120-160 beats/min
      - Gender: Women tend to have a faster HR than men
      - Exercise increases HR; trained athletes have a lower HR, but they have a higher SV
      - Body Temperature: HR increases with increased body temperature
      - Persistant HR changes
        
        Tachycardia: Abnormally high HR at 100 beats/min., can lead to fibrillation
        
        Bradycardia: Unusually slow HR, Can cause inadequate blood circulation in non-athletes. May be a favorable result of endurance training.
  - - - EDV = amount of blood collected in a ventricle during diastole (Normally 120 mL)
        
        Affected by preload
      - ESV = amount of blood remaining in a ventricle after contraction (Approx. 50 mL)
        
        Affected by contractility and afterload
    - - Preload (Amount ventricles are stretched by contained blood)
        
        Most important factor is preload stretching of cardiac muscle is venous return - amount of blood returning to heart
        
        Slow heartbeat and exercise increase venous return to the heart, increasing SV
        
        Blood loss and extremely rapid heartbeat decrease venous return and SV
      - Contractility (Cardiac cell contractile force)
        
        Negative inotropic agents decrease contractility
        
        Increased extracellular K+
        
        Calcium channel blockers
        
        Acidosis
        
        Positive inotropic agents increase contractility:
        
        Certain hormones (epinephrine, thyroxine, and glucagon)
        
        Ca2+ (required for binding to troponin, resulting in the binding of actin and myosin)
        
        Increased sympathetic stimuli
      - Afterload (Back pressure exerted by blood in the large arteries leaving the heart)
        
        NOT a major determinant of SV in normal individuals, but is important in people with hypertension
        
        Hypertension increases afterload → increased ESV, decreased SV
        More blood is going to be left over in the ventricles because the ventricles are having a hard time overcoming the pressure in the aorta