Changes in Blood Supply to Organs (DP IB Biology)

Changes in Blood Supply to Organs

• The role of the circulatory system is to supply the cells of the body with oxygen and nutrients, and to remove the waste products of metabolism

• The requirements of the cells in different parts of the body will differ depending on the activity levels of the body, e.g.

  • During exercise the muscles will require more oxygen and glucose to fuel muscle contraction, so will need an increased blood supply

  • After a meal the digestive system will require more oxygen and glucose to fuel digestion and absorption, so will need an increased blood supply

• The circulatory system can divert blood flow to increase or decrease the blood supply to different organs

  • This is achieved by vasodilation or vasoconstriction in the arterioles that supply the capillary beds in different parts of the body

• The blood supply to the organs may change as follows:

  • Skeletal muscles

    • During sleep the skeletal muscles are relaxed and blood flow to these muscles is relatively low

    • During wakefulness some muscle groups will be working to keep the body upright, and blood flow will increase

    • There will be a large increase in blood flow during physical exercise, as rapid contraction of many muscle groups will occur

  • Gut

    • Soon after a meal the blood flow to the gut will increase

    • Blood flow decreases during exercise so that more blood can be diverted to the skeletal muscles

  •  Brain

    • The blood flow to the brain remains relatively constant regardless of the activity levels of the body, as it carries out processes that need to occur all the time

    • Blood flow increases slightly during a stage of sleep known as REM

  • Kidneys

    • Blood flow does not change significantly on the basis of activity level, but will increase slightly during sleep and rest, and decrease slightly during prolonged exercise