Chapter 18: The Cardiovascular System: The Heart (The Cardiac Cycle Notes/Quiz)

• heart is muscle pump that simultaneously moves blood through pulmonary circuit of lungs and systemic circuit of remaining body tissues
• cardiac cycle
  • alternating contraction and relaxation of the heart that moves blood to both left and right sides of the heart simultaneously
  • oxygen poor blood flows into right side of heart into right atrium
  • blood then flows into Right atriventicular valve into the right ventricle
  • as ventricles contract blood is forced into right semilunar valve into pulmonary trunk\
  • Oxygenated blood flows into the left atrium through left AV valve into left ventricle 
  • as ventricle contract blood is forced through left semilunar valve into aorta
  • heart valves open only one direction due to force of blood/blood flow
    • prevents back flow of blood
  • to force blood through the heart chambers must alternatively contract, which is termed systole and relax which is termed, diastole
  • single cardiac cycle consists of 5 phases
    • takes place during ventricular diastole or ventricular systole
    • 1st phase
      • ventricles are relaxed and filling with blood
      • then contract (systole)
        • force blood to arteries
    • Last Phase
      • returns to ventricular diastole
      • after pumping blood out of heart ventricles begin to relax again
    • throughout cardiac cycle volume of blood in ventricles is measured through time
      • volume changes are the same for right and left ventricles
      • blood volume decreases during systole and volume increases during diastole
    • 1st phase (atrial contraction)
      • contraction of atria tops off ventricles filling them to maximum volume of blood
        • known as End Diastolic Volume (EDV)
      • now full ventricles begin to contract
    • Next 2 phases represent ventricular systole
      • 1st part of ventricular systole
        • Isovolumertric contraction
          • very small phase
          • pressure in ventricles begins to rise which closes AV valves
          • pressure is not yet high enough to open semilunar valves
            • so blood volume in venricles remains constant
          • ventricles contract as blood volume remains the same
          • ventricular volume remains the same in EDV
          • as ventricles continue to contract blood pressure builds and forces semilunar valves open
        • Ventricular Ejection
          • blood rushes from ventricles into pulmonary trunk and aorta
          • blood leaves ventricles, ventricular volume decrease
            • continues till reaching minimum volume known as End Systolic Volume (ESV)
            • marks beginning of ventricular diastole
    • Isovolumetric Relaxation
      • as pressure inside ventricles drops due to relaxation the semilunar valves shut
      • for brief time pressure is not yet low enough for ventricles to open AV valves so volume of ventricles remain constant
      • no change in ventricles volume 
      • blood volume remains at minimum because all valves into and out of ventricles are closed
    • Ventricular Filling
      • begins when pressure in ventricles becomes low enough that AV valves open
      • blood flow into left and right atria to av valves into ventricles
      • during this phase ventricular volume increases over time as ventricle is filled
      • passive flow of blood during this phase accounts for 80% of ventricular filling
      • remaining 20% of blood is forced into ventricles during atrial contraction
      • indicates start of another cardiac cycle

Questions/Quiz

1. What is the main function of the heart valves?

          to prevent backward flow of blood

2. When the atria contract, which of the following is true?

          the ventricles are in diastole

3. Which of the following is equivalent to the ventricular volume during isovolumetric contraction?

          the end diastolic volume (EDV)

4. Which of the following is true during ventricular systole?

          the AV valves are closed

5. During the ventricular ejection phase of the cardiac cycle, which of the following is true?

          the semilunar valves are open

6. Most of the decrease in ventricular volume takes place during which phase of the cardiac cycle?

          ventricular ejection

7. Which of the following is equivalent to the ventricular volume during isovolumetric relaxation?

          end systolic volume (ESV)

8. Most of the increase in left ventricular volume takes place during what phase of the cardiac cycle?

          ventricular filling


Note: The book I use for Anatomy and Physiology is called Human Anatomy and Physiology. Its the eight edition of the book. The Authors company of this particular book are/is Elaine N. Marieb and Katja Hoehn. The ISBN is: 978-0-321-74232-2 (9780321742322).Copyright 2010 by Pearson Education, inc.