Transcript Redistribution of Blood

Redistribution of Blood
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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
 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
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!
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Brain function maintained during exercise
Oxygen/nutrients required
 Reduced flow to abdominal organsliver, 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.