Chapter 17 Part D: Cardiac Output and Its Regulation

Review of Key Volumes

• End Diastolic Volume (EDV):

  • Amount of blood in each ventricle after diastole.
  • Normal EDV: ~120 mL.
  • Represents the maximum blood capacity of the ventricles.

• Stroke Volume (SV):

  • Amount of blood ejected from the ventricles during systole.
  • Normal SV: ~70 mL.

• End Systolic Volume (ESV):

  • Blood remaining in the ventricles after systole.
  • Normal ESV: ~50 mL.

Key Equations and Concepts

• Stroke Volume Calculation:

  • Formula: SV = EDV - ESV
  • Example Calculation: 120 mL (EDV) - 50 mL (ESV) = 70 mL (SV)

• Ejection Fraction (EF):

  • Indicates the percentage of blood ejected.
  • Formula: EF = (SV / EDV) x 100

Cardiac Output (CO)

• Definition:

  • Blood volume pumped by ventricles into pulmonary and systemic circuits per minute.
  • Indicator of heart function and efficiency, especially the left ventricle.

• Importance of Left Ventricle Efficiency:

  • Pumps oxygenated blood to active tissues.
  • Necessary for ATP production in cells.

• Cardiac Output Calculation:

  • Formula: CO = Heart Rate (HR) x SV
  • Units: milliliters per minute (mL/min)

Factors Affecting Cardiac Output

• Heart Rate (HR):

  • Increases in HR can increase CO and vice versa.

• Stroke Volume (SV):

  • Preload: Influenced by EDV; more volume leads to more stretch and higher preload (Frank-Starling Law).
  • Contractility:
    • Intrinsic ability of the heart to pump.
    • Higher contractility increases SV, reduces ESV.
  • Afterload:
    • Resistance the ventricles must overcome; higher afterload reduces SV.

Factors Influencing Heart Rate

• Chronotropic Agents:
  • Positive Agents: Increase HR (e.g., sympathetic stimulation, epinephrine).
  • Negative Agents: Decrease HR (e.g., parasympathetic activation).
• External Influences:
  • Body temperature can affect HR.

Overview and Study Tips

• Review slides from textbook pages 663.
• Understand the relationships between preload, contractility, afterload, and their impact on stroke volume and cardiac output.
• Make sure to comprehend the factors that increase or decrease cardiac output.

Conclusion

• Thorough understanding of these concepts is crucial for mastering cardiac function homework and tests. Study these dynamics closely for part D of chapter 17.