exercise and blood flow through special regions Flashcards
how do you calculate cardiac output by the Fick principle?
rate of O2 consumption (ml/min)/
arteriovenous O2 difference (ml/L of blood)
what happens to the local alveolar flow of blood when there is reduced alveolar O2 concentrations?
the local flow of blood is reduced by constriction of the blood vessels supplying it
what 3 different changes to blood flow to the heart can cause a decrease in coronary blood flow to the heart?
- decreased diastolic pressure in the aorta
- increased end diastolic volume (increases diastolic pressure so the aortic-ventricular pressure difference decreases)
- decreased diastolic filling time
what change of blood flow to the heart during exercise decreases blood flow to the heart?
decreased diastolic filling period
by how many times can work output of the heart increase during strenuous excercise?
up to 6-9 times
how much of the coronary blood flow to the heart is used AT REST?
70-80%
how is the increased demand of blood flow met?
can only be met by increased flow of blood to the heart by coronary circulation
how do you increase coronary blood flow?
- PRIMARILY by local factors causing dilation of cardiac blood vessels (by vasodilators e.g. adenosine)
how does SYMPATHEIC innervation affect coronary blood flow?
- indirectly via an increase in heart rate and contractility
- there is a high degree of sympathetic innervation to the coronary system but the exact role is unclear
what effect does noradrenaline (produced from sympathetic nerves) have on alpha one receptors on blood vessels?
vasoconstriction
what effect does adrenaline (produced from the adrenal medulla) have on beta 2 receptors which are only found on arterioles in SKELETAL MUSCLE?
vasodilation
