cardiovascular system

• functions of the heart :

  • double pump
  • diastole
  • systole
  • cardiac cycle
  • role of component parts
• Double pump :

  The heart is sometimes referred to as a double pump. It pumps blood through 2 separate circulatory systems:

  • Pulmonary - the right side of the heart receives deoxygenated blood from the body and it pumps it to the lungs

  • Systemic - the left side of the heart receives oxygenated blood from the lungs and pumps it to the rest of the body.
• Cardiac cycle :

  The flow of blood is called the cardiac cycle. This takes place, on average, about 70 times a minute.

  The part of the cycle when the ventricles are contracting is known as systole ie ventricles are contracting with the atrio-ventricular valves closed and the semilunar valves open.

  Diastole is when both ventricles and atria are relaxed, the atrio-ventricular valves are open, the semilunar valves are closed and the heart fills with blood
• Cardiac cycle


  Regulated by electrical signals
• Sinoatrial node (SA)


  • Located in the upper wall of the right atrium
  • Known as the 'pacemaker'
  • Responsible for setting the rhythm of the heart
  • Ensures both atria contract at the same time
• Atrioventricular node (AV)


  • Situated at the bottom of the right atrium of the heart
  • Responsible for delaying the electrical impulses from the SA node to allow time for blood to flow from the atrium into the ventricles
• Purkinje / Purkyne fibres


  • Fine specialised cardiac muscle fibres
  • Rapidly transmit impulses from the AV node to the ventricles
  • Bundles of this take the impulse from the AV node to the bottom of the ventricles
• Sinoatrial (SA) node


  A mass of specialised cells in the wall of the right atrium near the opening of the vena cava. The SA node is the pacemaker of the heart as it sets the heart rate and triggers contractions.
• Atrioventricular (AV) node


  is in the wall which separates the two ventricles. This allows the current to pass through.
• Purkyne fibres (or Purkinje fibres OR bundle of this)


  Fibres that carry the current down the middle of the ventricles to the base of the heart, causing contractions.
• Cardiac cycle


  • Heart contracts then relaxes

  • contractions are known as systole and relaxation is diastole
• • An ECG shows the spread of the electrical signal generated by the SA node as it travels through the atria, the AV valves and the ventricles.

  • A normal ECG trace shows 5 waves, named P,Q.R,S, and T • The waves represent the different electrical activity of the heart.

  • The different sections represent different activities in the heart.

  > P = shows atrial contraction (systole)

  > QRS = ventricular contraction (systole)

  > T= ventricles relaxing (diastole)