6.1.3 Control of heart rate

• Cardiac muscle is myogenic. What does this mean?

  It can contract and relax without receiving electrical impulses from nerves
• label parts of heart involved in control of heart rate

  A) sino atrial node

  B) bundle of his

  C) atrioventricular node

  D) purkenye tissue

  E) apex

  
• Describe the myogenic stimulation of the heart and transmission of a wave of electrical activity

  • SAN releases waves of electrical activity across atria
  • Causing atria to contract simultaneously
  • Non-conducting tissue between atria/ventricles prevents impulse passing to ventricles
  • Prevents contraction of ventricles
  • Waves of electrical activity reach AVN delaying impulse
  • atria fully contract and empty before ventricles contract
  • AVN sends wave of electrical activity down bundle of His, between ventricles to apex where it branches into Purkyne tissue
  • ventricles contract simultaneously from base up
• Where are chemoreceptors and pressure receptors located?

  Chemoreceptors and pressure receptors are located in the aorta and carotid arteries
• Describe the roles of chemoreceptors, pressure receptors, the autonomic nervous system and effectors when blood pressure or pH falls

  1. Baroreceptors detect fall in blood pressure and / or chemoreceptors detect rise in blood CO2 conc. or fall in blood pH

  2. Send impulses to medulla / cardiac control centre

  3. Which send more frequent impulses to SAN along sympathetic neurones

  4. So more frequent impulses sent from SAN and to / from AVN

  5. So cardiac muscle contracts more frequently

  6. So heart rate increases
• Describe the roles of chemoreceptors, pressure receptors, the autonomic nervous system and effectors when blood pressure of pH rises

  1. Baroreceptors detect rise in blood pressure and / or chemoreceptors detect fall in blood CO2 conc. or rise in blood pH

  2. Send impulses to medulla / cardiac control centre

  3. Which send more frequent impulses to SAN along parasympathetic neurones

  4. So less frequent impulses sent from SAN and to / from AVN

  5. So cardiac muscle contracts less frequently

  6. So heart rate decreases