Control of the heart 6.1.3

• The cardiac c is the ongoing system of contraction and relaxation of the atria and ventricles.
• Cardiac muscle contraction is known as systole.

  Cardiac muscle relaxation is known as diastole.
• Cardiac muscle is myogenic meaning it can contract and relax without receiving signals from nerves. The pattern of contractions controls the regular heartbeat.
• Add labels to this diagram detailing the system of controlling the heart.

  A) Bundle of HIS

  B) Purkyne Fibres

  C) The atrioventricular node

  D) The Sinoatrial node

  
• The sinoatrial node is where a heart contraction begins. It sends out a wave of depolarisation to the atrial walls, causing atrial systole.

  Depolarisation doesn't reach the ventricle due to issulation from collagen.
• As depolarisation form the SAN cannot reach the ventricles, the atreoventricular node sends out a wave of depolarisation to the bundle of HIS. This creates a delay between atrial systole and ventricle systole, ensuring the atria are empty.
• The bundle of HIS splits inhalf, onto a left and right side. Each of these sides of the bundle of HIS then splits again into many purkyne fibres that release waves of depolarisation causing simultanious ventricle systole.
• The autonomic nervous system is the section of the peripheral nervous system responsible for unconcious functions of the body.
• Within the medulla oblongata there are two centres with connections to the SAN, which act as cardioregulatory centres. These are the cardioacceleratory centre and the cardioinhibitory centre.