Integration of Cardiovascular Mechanism Flashcards
what is the function of capillaries
Site of gas, nutrient and water between blood and tissues
what is the function of veins
capacitance vessels containing most blood volume at rest
venous return must supply heart with sufficient blood to pump
what is the main regulator of HR
autonomic nervous system
what us the main regulator of Systemic vascular resistance
arterioles (vascular smooth muscle)
what effect does vasoconstriction have on SVR and MAP
increases SVR and MAP
what effect does vasodilation have on SVR and MAP
decreases SVR and MAP
what is resistance to blood flow directionally proportional to
blood viscosity and length of blood vessel
what is resistance to blood flow inversely proportional to
radius of the blood vessels
what is the most important faction in influencing resistnace/controlling vascular smooth muscle
changes in radius of arterioles
when there is a small decrease in the radius what effect is there on resistane
huge increase in resistance
what 2 extrinsic mechanisms control vascular smooth muscle
nerves and hormones
what nerves supply vascular smooth muscle
sympathetic nerve fibres ONLY (except brain)
baroreceptor reflex
what is the neurotransmitter of the sympathetic nerve fibres acting on vascular smooth muscle
noradrenaline
what is vasomotor tone and how does it affect SVR
blood vessels are always partially contracted at rest because of tonic discharge of sympathetic nerves resulting in continuous release of noradrenaline
what effect on vasomotor done does increasing sympathetic discharge have
increased vasomotor tone
VASOCONSTRICTION
what effect on vasomotor done does decreasing sympathetic discharge have
decreased vasomotor tone
VASODILATION
is there any parasympathetic activity of arterial smooth muscle
no only in penis and clitoris
what is the main hormone responsible for control of vascular smooth muscle control
Adrenaline
what receptors does adrenaline act on in vascular smooth muscle
A receptors in skin, gut and kidneys
B2 receptors in cardiac muscle and skeletal muscle