Special Circulation Flashcards
Where doe most coronary venous blood drain into
Via coronary sinus into the right atrium
What are the special adaptations of the coronary circulation
High capillary density
High basal blood flow
High oxygen extraction
Only supplied by increasing coronary blood flow
Controlled by Intrinsic and Extrinsic mechanisms
What does the intrinsic mechanism do
decreased Po2 decreases causes vasodilation of the coronary arteries
Metabolic Hyperaemia matches flow to demand
Adenosine (from ATP) is a potent vasodilator
What is Metabolic hyperaemia
The process by which the body adjusts blood flow to meet the metabolic needs of its different tissues in health and disease
What are the Extrinsic Mechanisms of Coronary blood flow
Sympathetic stimulation of heart results in coronary vasodilation despite vasoconstrictor effect
Circulating adrenaline activates Beta 2 adrenergic receptors which cause vasodilation
Coronary arterioles supplied by … but Over ridden by … as a result of increased … and …
Sympathetic vasoconstrictor nerves
Metabolic hyperaemia
Heart rate
Stroke
When does the peak left coronary flow occurs
During Diastole
What is the effect of shortening diastole (e.g. very fast heart rate)
decreases coronary flow
When does most of the coronary blood flow and myocardial perfusion occurs?
In diastole when subendocardial vessels from the left coronary artery are not compressed
Why is the resting blood flow in skeletal muscles low
Because of sympathetic vasoconstrictor tone
Why does skeletal muscle blood flow increase during exercise
Local metabolic hyperaemia overcomes sympathetic vasoconstrictor activity
Circulating adrenaline causes vasodilation
Increased cardiac output which increases skeletal muscle blood flow
What is the skeletal muscle pump
The skeletal muscles that large veins lie in between in limbs
What is the effect of skeletal muscle pump
Contraction of muscle aids venous return
One-way venous valves allow blood to move forward towards the heart
It reduces the chance for postural hypotension and fainting
What is postural hypotension
Increased blood pressure after standing up
What are Varicose veins
Blood pools in lower limb veins if venous valves become incompetent
