Redistribution of Blood

 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

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

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

 Increased blood flow to skeletal muscles skeletal muscles  Increased blood flow to the skin the skin  Increased blood flow to coronary vessels coronary vessels  Same blood flow to the brain  Reduced flow to kidneys  Reduced flow to liver

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

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

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

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

Task

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

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

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.

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!!

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

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.