Heart & Vagus Nerves

• Effect of sympathetic nerves on the heart

  • Increase heart rate
  • Increase force of contraction
• Sinoatrial (SA) node


  Located in the right atrial wall of the human heart
• Excessive vagal stimulation of the heart

  Decrease in heart rate
• Vagus nerve stimulation applied to the frog heart

  Heart rate slowed and eventually stopped
• In the absence of neural and hormonal influences, the SA Node generates action potentials at a frequency of about 100 times per minute
• Resting heart rate is about 70 BPM
• Spontaneous depolarization rate


  • Fastest - SA node