Topic 27 - The cardiac cycle

Question 1

Words to include

Answer 1

• Electrical activity
• Mechanical properties
• Cardiac cycle
• Systole
  
  • Contraction
• Diastole
  
  • Relaxation
• Pressure
  
  • Pressure
  • Pulmonary veins
  • Left atrium
  • Left ventricle
  • Aorta
  • Valves
  • Blood flow
• Volume
  
  • Diastole
  • Diastolic volume
  • EDV
  • ESV
  • SV
• Valves
  
  • Semilunar valves
    
    • Aorta
    • Pulmonary artery
  • Cuspid valves
    
    • Atria
  • Diastole
  • Systole
• Heart sounds
  
  • 1^st sound
    
    • Cuspidal valves
      
      • Systolic heart sound
    • Vibration
    • Muscle contraction
    • Turbulence
  • 2^nd sound
    
    • Diastolic
    • Semilunar valves
    • Physiologically split
      
      • Aortic valve
      • Semilunar valve
      • Pulmonary artery
  • Sub-audible sound
  • 3^rd sound
    
    • Rapid filling
    • Ventricle
  • 4^th sound
    
    • Turbulent flow
    • Atrial contraction
  • Stenosis
    
    • Murmurs
• Jugular pressure
  
  • V. jugularis
• ECG
• Pressure values
• Valves
• Atrial contraction
  
  • P-wave
  • Cuspidal valves
  • Semilunar valves
• Isovolumetric contraction
  
  • QRS-complex
  • Ventricular volume
• Rapid ejection
  
  • Semilunar valves
  • Cuspidal valves
• Reduced ejection
  
  • Semilunar valves
  • Cuspidal valves
• Isovolumetric relaxation
• Rapid filling
  
  • Semilunar valves
  • Ventricles
• Reduced filling
  
  • Semilunar valves
  • Ventricles
• Ventricular systole
• Ventricular diastole

Question 2

Introduction

Answer 2

• The coordinated electrical activity and mechanical properties of the heart make it possible that the heart functions all trough a lifetime
  
  • The basic unit of this functioning that is repeated uninterruptedly is the cardiac cycle
• Composed of two elements:
  
  • Systole (contraction)
  • Diastole (relaxation)

Question 3

Total length of cardiac cycle in dog

Answer 3

800 msec

Question 4

Parameters of the cardiac cycle

Give the parameters of the cardiac cycle

Answer 4

1. Pressure
2. Volume
3. Valves
4. Heart sounds
5. Jugular pressure

Question 5

Parameters of the cardiac cycle

Pressure

Answer 5

The minute to minute changes of pressure values in the pulmonary veins, left atrium, left ventricle, and the aorta determine the position of the valves and accordingly the flow of blood in these compartments

Question 6

Parameters of the cardiac cycle

Volume

Answer 6

• The volume is constant in the isovolumetric stages of cardiac cycle
• In the early ejection phase of systole the volume of the ventricle decreases rapidly and then the rate of emptying slows down
• During diastole a rapid filling phase is followed by reduced filling (EDV, end diastolic volume)
• The difference of EDV and ESV is the SV

Question 7

Parameters of the cardiac cycle

Valves

Answer 7

• Semilunar valves:
  
  • ​Diastole: closed
  • Systole: open
• Cuspid valves:
  
  • ​​Diastole: open
  • Systole: closed

Question 8

Parameters of the cardiac cycle

Heart sounds

Answer 8

• 1^st sound:
  
  • During and just after the closure of the cuspidal valves (systolic heart sound)
  • Three components:
    
    • Vibration of muscle contraction
    • Turbulence of blood due to closure of the valves
    • Turbulence of blood caused by fast ejection
• 2^nd sound:
  
  • Diastolic, during closure of semilunar valves
  • Physiologically split:
    
    • First the aortic valve closed, followed by the semilunar valves of the pulmonary artery

​

• Sub-audible sound

​

• 3^rd sound:
  
  • Rapid filling of the ventricle
• 4^th sound:
  
  • Turbulent flow caused by the atrial contraction

​

• Stenosis
  
  • ​Insufficiency generate distorted heart sounds (murmurs)

Question 9

Parameters of the cardiac cycle

Jugular pressure

Answer 9

With the sudden onset of cardiac relaxation at the beginning of the diastole the basis of the heart moves cranially and this increases the pressure in the v. jugularis

Question 10

Cardiac cycle

Answer 10

By analyzing the ECG and pressure values, we can easily understand the blood flow in the heart and the role of the valves

1. Atrial contraction
   
   • Begins after P-wave
   • Cuspidal valves are open
   • Semilunar valves are closed
2. Isovolumetric contraction
   
   • Begins with the QRS complex
   • All valves are closed
     
     • Ventricular volume is unchanged
3. Rapid ejection
   
   • Semilunar valves: open
   • Cuspidal valves: closed
4. Reduced ejection
   
   • Semilunar valves: open
   • Cuspid valves: closed
5. Isovolumetric relaxation
   
   • All valves are closed
   • Isovolumetric relaxion: no volume changes
6. Rapid filling
   
   • Semilunar valves: open
   • The major volume of the blood flows into the ventricles
7. Reduced filling
   
   • Semilunar valves: open
   • More blood flows passively into the ventricles from the atria