Controlling heart rate

• Medulla oblongata= responsible for controlling heart rate.
• Increasing heart rate:

  • Impulses sent through sympathetic nervous system.
  • Transmitted by the accelerator nerve.
• Decreasing heart rate:

  • Impulses sent through parasympathetic nervous system.
  • Impulses transmitted by the vagus nerve.
• Baroreceptors= detect changes in blood pressure.

  • Present in the walls of the aorta, carotid arteries, vena cava.
• Chemoreceptors= detect changes in the level of chemicals in the blood. Eg: carbon dioxide.

  • Preset in the walls of the aorta and the carotid artery.
• 1. Baroreceptors or chemoreceptors detect changes and send impulses to the medulla oblongata.
  2. The medulla oblongata increases or decreases the frequency of impulses along the sympathetic or parasympathetic nerve to the SAN.
  3. The SAN then increases or decreases the heart rate.
• Heat rate also influenced by hormones.

  • Adrenaline and noradrenaline are released which affects the SAN which increases or decreases the heart rate.