control of blood flow

• define redistribution of blood

  • During exercise more blood needs to be redirected to muscles in order to meet increased demand
  • Redirecting of blood flow during exercise is called the VASCULAR SHUNT MECHANISM
• The vascular shunt is important to ...

  • increased oxygen supply to working muscles ( allows contraction )
  • inc blood flow to heart for more blood around body
  • removed waste products from muscles produced during exercise ( lactic acid and C02)
  • inc blood flow to skin to help us cool down ( thermal regulation )
• Define vasodilation and vasoconstriction.

  vasodilation - widening of blood vessels to increase blood flowvasoconstriction - narrowing of blood vessels to reduce blood flow
• define arterio-venous difference


  The difference between the oxygen content of the arterial blood arriving at the muscles and the venous blood leaving the muscles
• explain A-V02 diff at rest and exercise

  • At rest the difference is low as muscles don't require much oxygen
  • During exercise the muscles need more o2 for energy so the difference is high as more o2 is extracted by muscles
• describe how process of vascular shunt happens

  • chemoreceptors detect increase in carbon dioxide
  • baroreceptors detect blood pressure
  • vasomotor centre in the medulla stimulates vascular shunt
  • vasoconstriction in arterioles at non active tissues + pre-capillary sphincters contract to decrease blood flow to non active tissues
  • vasodilation in arterioles at muscles + pre-capillary sphincters relax to increase blood flow to working muscles
• pre-capillary sphincters


  rings of cartilage leading up to muscle open up when they relax