Redistribution of Blood

1. Redistribution of Blood

2. We only have 4-5 litres of blood in our body • Huge capillary network • More space for blood than there is blood! • Competition for blood between regions of the body • Especially during exercise

3. In Pairs……… • Discuss the redistribution of blood during exercise to the: skeletal muscles, coronary vessels, brain, kidney and liver.

4. Which body parts need more oxygen?Which parts still need the same?Which parts can have a reduced flow?

5. Increased blood flow to skeletal muscles • Increased blood flow to the skin • Increased blood flow to coronary vessels • Same blood flow to the brain • Reduced flow to kidneys • Reduced flow to liver

6. Shunting of Blood • Achieved by vasodilatation (opening) and vasoconstriction (closing) of the arterioles that supply the blood entering the capillary beds. • Within the arterioles – rings of circular muscle act as sphincters • Ring of muscle contracts and the size of the opening decreases reducing the blood flow

7. Vasoconstriction • Controlled by the sympathetic nervous system • Stimulation by impulses from nerves causes the smooth muscle in arteries and pre capillary sphincters to contract • Vasoconstriction • Reduced blood flow

8. Vasodilatation • The same sympathetic nerves act as vasodilataters which increase the diameter of the vessel and so the blood flow. Other local factors that cause this; • Drop in O2 and increase in CO2= Increase in acidity • Movement in the joints and tendons- instant vasodilatation as result of muscle activity

9. Explain how redistribution of blood occurs during exercise. • A. Increase in CO2 levels/acidity/ decrease in O2 levels/pH/ chemoreceptors • B. Movement of joints/tendons/ mechanoreceptors/proprioceptors • C. Vasomotor centre/medulla • D. Autonomic/sympathetic nervous system/(nor)adrenaline • E. Pre-capillary sphincters/rings of circular/smooth muscle • F. Vasodilation to areas needing blood/muscles • G. Vasoconstriction of areas not needing so much blood/kidneys/liver/ gut

10. Task

11. Blood Flow Skeletal Muscles; To supply the muscles with oxygen and nutrients, remove waste products Coronary arteries; Blood supply is increased here to the heart so it can beat stronger and faster

12. Blood Flow Skin; • Increased flow here as heat is generated by the working muscles and we need to maintain a constant temp. • Need to lose heat- radiation and evaporation • Radiation- body hotter than its’ environment. Vasodilatation of capillaries near skin warms the skin so allowing heat to be lost

13. Blood Flow • Evaporation; sweating • Sweat forms a layer of water on the skins’ surface. When the water evaporates it loses heat and so cools the skin Exercise= sweat and skin reddens due to increase blood flow.

14. Where does the blood come from? • Brain- stays the same as it can’t switch off! • Brain function maintained during exercise • Oxygen/nutrients required • Reduced flow to abdominal organs- liver, kidney and digestive organs • Vasoconstriction • This is why you should not eat before exercise- Puky!!

15. Explain why performers should not eat immediately before exercise. • During exercise, less blood goes to the gut • But, blood/oxygen needed in gut for digestion of food • Less blood/oxygen available to muscles

16. Lets Recap….. • Begin to exercise… • Increase in demand for O2 and increase in need to get rid of waste products- CO2 and Lactic. • Increases in blood acidity detected by chemoreceptors • Stimulates sympathetic nervous system • Pre capillary sphincters in non-essential areas contract and cause vasoconstriction • Pre capillary sphincter in skeletal muscle relax and cause vasodilation.