Mechanism of Heartbeat

 

 
10.3 Mechanism of Heartbeat
 
Heartbeat:
 
Source: [Text book Biology Form 4]
 
  • Average heartbeat = 72 times/minute. 
  • Sinoatrial nodes (SA) and atrioventricular nodes (AV) functions to ensure the heartbeat beats at a proper rate.
  • Sinoatrial nodes are also known as the pacemaker of the heartbeat. 
 
Pacemaker sets and coordinates the contraction of the heart but it is also influenced by:
 
  • Nervous system.
  • Endocrine system.
  • Sympathetic and parasympathetic nerves.
  • Adrenaline (hormone).
 
The sequence of the contraction of the heart muscles that pump the blood:
 
  • SA nodes produce electrical impulses.
  • Electrical impulses spread rapidly to both atria, causing the atria to contract simultaneously.
  • The contraction of the atria causing the blood pressure in the atria to increase and pump the blood to the ventricle. 
  • Electrical impulses arrived at the AV nodes.
  • The electrical impulses spread through the bundle of His, and Purkinje fibers until it reaches the heart's apex.
  • The electrical impulses spread to both ventricles and causing them to contract simultaneously.  
  • This causing the blood pressure in both ventricles to increase and pump the blood to the lungs and to all body parts.