Integration of cardiovascular mechanisms Flashcards
Factors which influence MAP?
Heart Rate
Stroke Volume
Systemic vascular resistance
Main site of systemic vascular resistance?
Arterioles
Components of cardiovascular system?
Heart - pump
Arteries - passageway of blood from heart to tissues
Arterioles - major resistance vessels
Capillaries - Site of gas exchange, nutrients and water between blood and tissues
Veins - Contains most of blood volume during rest - passageways of blood from tissues to heart
What must venous return provide?
The heart with sufficient blood to pump
Name for veins?
Capacitance vessels
How is HR mainly regulated?
Autonomic nervous system
How is SV mainly regulated?
Preload
Myocardial contactility
Afterload
CO equation=
CO= HR x SV
How can MAP be estimated?
DBP + 1/3 pulse pressure
How is systemic vascular resistance regulated?
By vascular smooth muscles
What does contraction of vascular smooth muscles cause?
Vasoconstriction and decreases SVR and MAP
What are vascular smooth muscles controlled by?
Intrinsic and extrinsic mechanisms
What is resistance to blood flow directly proportional tp?
Blood viscosity and length of blood vessel
What is resistance to blood flow inversely proportional to?
Radius of blood vessel to the power of 4
Resistance to flow equation?
R proportional to n.l/r^4 n=blood viscosity L= length of blood vessel r= radius of blood vessel R= resistance to flow
What does extrinsic control of vascular smooth muscle involve?
Nerves and hormones
If we constrict muscle in arterioles what happens?
Increases resistance and decreases flow
What are vascular smooth muscles supplies by?
Sympathetic nerve fibers
Vascular smooth muscle neurotransmitter and receptor it works on?
Noradrenaline
acts on alpha receptors
Vasomotor tone?
Vascular smooth muscle partially constructed at rest
Control of vascular smooth muscles via hormones?
Adrenaline
Organ specific
Depends on predominant type of receptor
What does adrenaline acting on alpha receptors cause?
Vasoconstriction
What causes vasodilation?
Adrenaline acting on beta 2 receptors
Where are alpha receptors predominantly found?
Skin
Gut
Kidney arterioles
What receptor is found on cardiac and skeletal muscle arterioles?
Beta2 receptors
Other hormones which extrinsically affect vascular smooth muscle control?
Angiotensin 2- causes vasoconstriction
Antidiuretic hormone- causes vasoconstriction
What do local metabolic changes within an organ influence?
Contraction of arteriolar smooth muscles
What factors causes relaxation of arteriolar smooth muscles?
Vasodilation
Metabolic hyperaemia
What do other local chemicals released within an organ influence? and when are they released
Contraction of arterial and arteriolar smooth muscles
Following a tissue injury or inflammation
Examples of humoral agents which cause contraction of arteriolar smooth muscles resulting in vasoconstriction?
Serotonin
Thromboxane A2
Leukotrienes
Endothelin
Endothelin?
Potent vasoconstrictor released from endothelial cells- production stimulated by various agents which cause vasoconstriction
What s endothelium important for?
Maintenance of vascular health
What can endothelial damage/dysfunction be caused by?
High BP
High cholesterol
Diabetes
Smoking
What are endothelial produced vasodilators?
Anti-thrombotic
Anti-inflammatory
Anti-oxidants
Endothelial produced vasoconstrictors are?
Pro-thrombatic
Pro-inflammatory
Pro-oxidants
What does a cold temperature cause?
Vasoconstriction
What does warmth cause?
Vasodilation
What is vasomotor tone caused by?
Tonic discharge of sympathetic nerves resulting in continuous release of noradrenaline
What will increased sympathetic discharge cause in vascular smooth muscles?
Increase the vasomotor tone
Vasoconstriction
What causes decreased vasomotor tone (vasodilation)?
Decreased sympathetic discharge to vascular smooth muscle
There is no significant parasympathetic innervation of arterial smooth muscles. True or False?
There is no significant parasympathetic innervation in arterial smooth muscle EXCEPT in penis and clitoris.
What hormone controls vascular smooth muscle?
Adrenaline from the adrenal medulla
Explain the affect of adrenaline?
Largely organ specific - depends on predominant type of receptor
What does adrenaline acting on alpha receptors cause?
Vasoconstriction
What are important in immediate control of BP?
Angiotensin 2
ADH
Intrinsic control of vascular smooth muscles can override extrinsic controls? True or False?
True
What do intrinsic control of vascular smooth muscle include?
Chemical and physical factors
Intrinsic control of vascular smooth muscles?
These match the blood flow of different tissues to their metabolic needs
