control of heart rate

• CNS: Central Nervous System, consists of the brain and spinal cord.
• PNS: Peripheral Nervous System, consists of all the nerves outside the brain and spinal cord
• PNS:

  • 2 different systems: Somatic nervous system & Autonomic nervous system
  • Somatic nervous system - controls conscious activities
  • Autonomic nervous system - controls unconscious activites
• Autonomic system is split into Sympathetic and Parasympathetic nervous systems

  • Sympathetic - ' fight or flight', prepares body for action
  • Parasympathetic - 'rest & digest' calms body down
  • Autonomic system concerned with control of heart rate
• Cardiac muscle is MYOGENIC- contracts and relaxes without signals from nerves
• process of HR:

  • begins in Sinoatrial node, SAN - pacemaker - sets heartbeat rhythm by sending regular waves of electrical activity to atrial walls
  • Bundle of non-conducting collagen tissue prevents waves of electrical activity to travel to the ventricles from atria-> instead travel to the Atrioventricular node
  • AVN passes waves of electrical activity to bundle of His
  • slight delay before ANS reacts
  • Bundle of His conducts waves from ventricles to apex of heart
  • BOH splits into Purkyne tissues
  • Purkyne tissue in l & r ventricle muscular walls -simultaneous contraction
• SAN:

  • small mass of tissue at the top of the right atrium wall and at the opening of the superior Vena Cava
  • PACEMAKER- at regular intervals sens waves of electrical activity to atrial walls
• AVN:

  • Passes ave of electrical impulse to bundle of His
  • slight delay before it acts to ensure atria is empty
  • located in the interatrial septum
• Bundle of His - A bundle of muscle fibers that contracts to pump blood through the heart.

  • split into finer muscle fibres in left and right muscular walls in ventricles
  • in endocardium
• • After apex of heart contracts, during systole the papillary muscle contract to prevent backflow of blood by closing of AV valves - attached to AV by chordae tendinae
  • prevent the valves from prolapsing