15. Cardiovascular Control

• inputs from chemoreceptors, baroreceptors and cardiopulmonary receptors enter into the NTS of medulla
• NTS of medulla outputs:

  • vagal nerve
  • sympathetic nerve
• arterial baroreceptors = baroreceptors found in the carotid sinus and the aortic arch

  • respond to stretch in the vessel walls brought about by the changes in the blood pressure
• at normal blood pressure there is some activity in the baroreceptors afferents

  • increase in number of action potentials when increased blood pressure
  • informs CNS about the magnitude of change in blood pressure
• increase in blood pressure -> medulla and NTS

  • increases vagal outflow (nucleus ambiguous) and decreases sympathetic outflow (rostral ventral lateral medulla)
  • decreased heart rate, contractility and TPR
• decreased blood pressure -> reflex vasoconstriction, especially in GIT
• slope of the stimulus response curve = baroreflex sensitivity
• the baroreflex is most sensitive around the operating point - set at a normal blood pressure in a healthy person
• the baroreflex will be reset if high blood pressure is maintained for more than a few minutes

  • prevents heart rate falling in exercise
  • can be inhibited to allow blood pressure to rise in defence response