Integration Of Cradiovascular Mechanisms Flashcards
What regulates the stroke volume
Preload
Myocardial contractility
Afterload
What is the map eqn
Map = DBP + 1/3 difference between SBP and DBP.
What is resistance of blood vessels directly proportional to
Blood viscosity and length of blood vessels
Inversely proportional to radius of blood vessel to power of 4
What is the eqn for resistance
R= n.L/ r (4)
How is the resistance of the blood vessel mainly controlled
By vascular smooth muscle through changes in radius of arterioles
What is the extrinsic control of vascular smooth muscle
Nerves and hormone
- nerves baroreceptors
- symp nerve w/neurotransmitter noradrenaline at alpha receptors
- partial constriction at rest VASOMOTOR TONE
-hormones adrenaline act on alpha receps vasoconstriction and beta receps vasodilation
Where are alpha and beta receps
Alpha - receps n skin, but, kidneys
Beta - receps in cardiac and skeletal muscle
What are the hormones which control vasc smooth muscle
Angiotensin 2 - causes vasoconstriction ADH - vasoconstriction These match blood flow to metab needs Override extrinsic Include local chem and physical factors
What does local metabolic changes do to the contraction of arteriolar smooth muscle
Vasodilation caused by
- decreased local po2
- increased local pco2
- increased hydrogen ion
- increased extracellular potassium ion
- increased osmolarity of ECF
- adenosine release
What are some local changes in chemical factors
Decrease in these cause vasodilation
- histamine
- prostaglandins
- bradykinin
- nitric oxide ( continually released by endothelial cells)
What is nitric oxide
Continually produced by vasc endothelial from amino acid by L-arginine through enzymatic action of nitric oxide synthase (NOS)
Potent vasodilator short half life imp in reg of blood supply and maintainence vasc health
Flow dept NO formation
Receptor stimulated many vasoactive substances
No diffuses into adjacent smooth muscle where activates form of cGMP which is. Signalling smooth muscle relaxation
What are some chemical agents which cause vasoconstriction
Serotonin
Thromboxane A2
Leuktrienes
Endothelin - potent vasoconstrictor released form endothelial cells
Prod Stim by angiotensin2 and ADH
What are some physical control on vasc smooth muscle
Temp - cold ( vasoconstriction ) and hot ( vasodi)
Myogenic response to stretch - map rises constrict and map falls dilate
Sheer stress - dilation of arterioles causes sheer stress in arteries upstream to make them dilate causes blood flow to metab active tussles
What are factors influencing venous return
Increase return by:
- increases venomotor tone
- increases skeletal muscle pump
- increases RESP pump
- increases atrial pressure which inc EDV inc SV
- increase blood vol
What is the venomotor tone
The veins are capacitance vessels that contain most of blood volume under rest
Venous smooth muscles supplied. With symp nerve fibres
Stim gives venous constriction
Increased venomotor tone increases venous return.
What is the skeletal muscle pump
Large veins in limbs lie between skeletal muscles
Contraction of muscles aid venous return
One way venous valves allow flow unidurectional
Muscle activity increases venous return to heart
What are some acute cvs responses to exercise
Symp nerve activity increases
HR and SV increase ehich inc co
Symp vasomotor nerve reduce flow to kidneys and guts b
In skeletal and cardiac muscle, metab hypercapnia overcomes vasomotor drive - vasodi
Blood flow inc
What is the effect of symp Stim on the heart
Symp Stim increases heart rate by increasing the rate of firing of sa node and decreases av nodal delay
Symp Stim also increasesd force of contraction
What are some chronic cvs responses to exercise
Regular aerobic exercise helps reduce blood pressure
Mechanism not fully understood and controversial
Multi factorial
Include :
- reduction of symp tone and noradrenaline levels
- cardiac remodellifn
- increased parasymp tone
- reduction in plasma renin levels
What mainly regulates the heart rate
Autonomic nervous system
