Innervation of Myocardium

• Innervation of the myocardium:

  • the sarcolemma of myocardial fibres contain sympathetic receptors (particularly the ventricular myocardium)
  • these receptors are sensitive to circulating levels of the hormone epinephrine and to the neurotransmitter released by the sympathetic nervous system, which is norepinephrine
  • activation of the sympathetic nervous system results in the opening of more calcium ion channels than usual
• Innervation of the myocardium:

  • switching on/off or upgrading/downgrading sympathetic activity provides a mechanism for opening more or less calcium ion channels
  • thereby upgrading or downgrading calcium induced calcium release and manipulating force production and the volume of blood ejected
• Innervation of the myocardium:

  • an increased force of contraction caused by sympathetically increased calcium influx is known as inotropy or increased contractility