Physiology wk6 Flashcards
what is the role of each blood vessel
Arteries – blood delivery
Small arteries/arterioles – flow regulation
Capillaries – fluid/nutrient exchange
Venules – collection
Veins – return
what vessels are part of macrocirculation
- Conduit arteries
- Feed arteries
what vessels are part of microcirulation
- Resistance arteries
- resistance arterioles
- terminal arterioles
- capillaries
what influences help vasodilation
- neural
- hormonal – epinephrine/norepinephrine and AMP
- myogenic – lowers flow going to brain to reduce pressure going to the brain
what is hyperaemia
blood flow increases to the metabolic activity of a tissue/organ
what is hyperaemia stimulated by
- tissue hypoxia = not enough o2 delivery
- co2 increase
- pH decrease
- lactate production
- products of ATP
- osmolality
- potassium levels
what do prostaglandis do
these increase the amount of swelling at damaged tissues
what percentage of blood flow goes to muscles at rest and during exercise
20 at rest, rises to 80-85 during exercise
what causes such a massive increase in blood flow
redistribution from inactive muscles and reduced blood flow to inactive organs
what is autoregulation
- blood flow to meet metabolic demands of tissue
- Magnitude of vasodilation is proportional to size of recruited muscle mass
- Due to local changes (increased NO, prostaglandins, ATP and adenosine
what is vascular shunting
blood splits off when traveling to the liver, this shunts blood to the hepatic artery to deal with products to be treated in the liver
how does blood flow decrease
through sympathetic vasoconstriction and circulating catecholamines, o2 extraction increases to compensate (GLUT1 transporters sent out)
what happens after splanchnic blood flow is constricted
venous return is increased
what does the portal vein do
takes blood back to the heart through the liver, people with spine damage will have higher volumes in their portal vein as they cant shunt blood away efficiently
what are the ways of sympathetic neural control of skin blood vessels
- Adrenergic vasoconstrictor (non hairy skin) – noradrenalin neurotransmitter
- Cholinergic vasodilator (hairy skin) – acetylcholine neurotransmitter
why does vasodilation occur at higher thresholds during exercise than rest
- During exercise blood flow is shifted from core to surface to help cool
- Muscle pump cant assist in aiding venous return
- Filling of the heart is reduced and vasoconstriction must occur to maintain BP
what happens to renal blood flow when hr increases
it will decrease alongside the digestive system
how much of total cardiac output goes to the brain
20%
why is habitual exercise good for the brain
maintains its size and usefulness
what are the measures of brain blood flow
Brain perfusion imaging technique - MRI
Transcranial doppler – measures blood velocity as an index of flow
Near-infrared spectroscopy (NIRS) – measures balance of oxygen supply and demand at capillary level in cerebral cortex
what happens to brain blood flow during exercise
is directly proportional to co2 levels, rises and falls at the same time/rate
what can causae fainting
major increase or decrease in blood flow/pressure
what happens to Brain blood flow during different bouts of exercise
with higher intensities there is more bbf
what are the two endothelial derived relaxing factors (EDRF’s)
nitric oxide
prostoglandins
