redistribution of blood Flashcards
vascular shunt mechanism
the redistribution of cardiac output
why should sport performers not eat less than an hour before competition
a full gut will result in more blood being directed to the stomach instead of the working muscles and this would have a detrimental effect on performance as less oxygen is being made available
what happens to blood flow to the brain during exercise
must remain constant to ensure brain function is maintained as the brain needs oxygen for energy
what happens to blood flow to heart during exercise
more blood needs to go to the heart because the heart muscles need oxygen for energy to beat faster
what happens to blood flow to the skin during exercise
more blood goes to the skin because energy is needed to cool the body down
what is blood pressure and blood flow controlled by
vasometer centre located in the medulla oblongata in the brain
vasodilation
widening of the blood vessels to increase blood flow into capillaries
*occurs after changes being detected by chemoreceptors
vasoconstriction
narrowing of blood vessels to reduce blood flow into capillaries
what happens when sympathetic stimulation increases
when sympathetic stimulation increases, vasoconstriction occurs and blood flow reduces so it can be redistributed to other parts of the body such as muscles
what happens when sympathetic stimulation decreases
vasodilation occurs and increases blood flow to that body part
pre-capillary sphincters
aid blood redistribution
- tiny rings of muscle located at the opening of capillaries
- when they contract, blood flow is restricted through the capillary and they they relax blood flow is increased
- during exercise, the capillary networks supplying skeletal muscle will have relaxed pre-capillary sphincters to increase the blood flow and therefore saturate the tissues with oxygen
why is redistribution of blood important
- increase the supply of oxygen to the working muscles
- remove waste products from muscles e.g. C02 and lactic acid
- ensure more blood goes to the skin during exercise to regulate body temp and get rid of heat through sweating
- direct more blood to the heart as it is a muscle and requires extra oxygen during exercise
arterio-venous difference
the difference between the oxygen content of arterial blood arriving at the muscles and the venous blood leaving the muscles
what is the arterio-venous difference at rest
low as not much oxygen is required by the muscles
what is the arterio-venous difference during exercise
much more oxygen is needed from the blood for the muscles so arterio-venous difference is high
- an athletes muscles demand a larger amount of oxygen, causing there to be an increase in the volume of oxygen in the muscle capillaries and a lower volume in the veins
- As the volume of oxygen in the arteries remains constant, there is a larger difference in the oxygen volume in the veins and arteries and therefore a larger arteriovenous oxygen difference
what effect will an increase in arterio-venous difference have
affects gaseous exchange at the alveoli so more oxygen is taken in and more carbon dioxide is removed
how to increase arterio-venous difference
training as trained performers can extract a greater amount of oxygen from the blood
explain how blood is redistributed to working muscles
- increase in C02 detected by chemoreceptors
- send impulse to medulla and will redistribute blood flow by vasoconstriction and vasodilation
- SNS brain sends impulse causing pre-capillary sphincters to relax so blood flow increases
explain how increased C02 causes increased HR
- detected by chemoreceptors
- impulse sent to medulla
- sympathetic impulse sent to SAN
- decrease in parasympathetic nerve impulse
