9.8 control of heart rate

• nodes involved in heart contraction...

  • Sinoatrial node - right atrium wall
  • Atrioventricular node - right atrium wall seperating atria
• two types of receptors

  • chemoreceptors = in aorta wall + carotid artery. detect carbon dioxide conc.
  • baroreceptors = in aorta wall + carotid artery. detect blood pressure
• control centre


  • in medulla oblongata
  • coordinates response to changes in blood pressure and carbon dioxide concentration
  • controls acceleratory and inhibitory centre
• body response to increased CO2 conc

  
  

  • detected by baroreceptors(bp) or chemo (co2) in aorta
  • impulse sent to cardiac (acceleratory) centre
  • impulse sent down sympathetic nervous system to SAN
  • stimulates release of noradrenaline, increasing heart rate
• body response to decreased CO2 conc

  • detected by baroreceptors(bp) or chemo (co2) in aorta
  • impulse sent to cardiac (inhibitory) centre
  • impulse sent down parasympathetic nervous system to SAN
  • stimulates release of acetylcholine, decreasing heart rate
• as carbon dioxide concentration decreases, pH of the blood increases
• shocks cause the SAN to stimulate the medulla which...

  • increases frequency of impulses in sympathetic
  • release of adrenaline in blood
  • adrenaline binds to target cell receptors in SAN
  • increasing heart rate