Manipulating cardiac function Flashcards
What is EC50
Concentration of drug that produces 50% of maximal response (how much of the drug we need to ilicit a response)
What will happen to the dose response curve in the presence of a competitive antagonist
Parrallel shift to the right, EC50 will increase due to the presence of a competitive antagonist
Cardiac output
= heart rate x stroke volume
Which neurotransmitter is released following sympathetic innervation of the heart
Noradrenaline, increasing HR and contraction force
Which neurotransmitter is released following parasympathetic innervation of the heart
Acetylcholine, can reduce HR and force of contraction
Where does noradrenaline act
Binds to alpha and beta receptors
Acts in the heart tissue and in the vasculature
What does Isoprenaline bind to
Only binds beta receptors
What is the affect of isoprenaline on HR and BP
Increases Hr, but decreases BP
What does the introduction of isoprenaline tell you about the role of beta receptors in the heart tissue and vasculature
- Beta receptors in heart tissue increase HR
- Beta receptors in the vasculature are vasodilators
What are the roles of alpha, beta 1 and beta 2 receptors
- Alpha= cause vasoconstriction
- Beta 1= in the heart, increase HR and force of contraction
- Beta 2= in the vasculature, cause vasodilation
What is prazosin
Adrenergic antagonist (alpha 1 blocker)
When prazosin was added the affect of noradrenaline was unchanged, what does this tell you
No alpha 1 receptors in the heart
What do alpha 1 receptors do
vasoconstriction
- so prazosin can block the BP increase from noradrenaline
What is propanolol
An adrenergic antagonist (beta 1 and 2 blocker)
How does propanolol
Will block noradrenaline, menaing HR does not change
Propanolol has little affect on BP what does this mean about noradrenaline and vasculature
Shows the dominant affect of noradrenline in the vasculature is alpha related
What is atenolol
adrenergic antagonist (beta 1 blocker)
What happens to the affect of noradrenaline in the presence of Atenolol
Affect on HR is reduced, shows that Beta 1 receptors are located in cardiac tissue (also reduction in BP likely due to reduced cardiac output)
From these tests, what do B-adrenoreceptors regulate
Regulate HR (B1 or B2)
What does blocking B-adrenreceptors also lead to?
Increase noradrenaline’s alpha 1 effect (slight increase to vasoconstriction)
What do Beta 1 and Beta 2 receptors regulate resepectivley
B1 adrenoreceptor in heart
Vasodilation regulated by B2
Describe the full affects noradrenaline (sympathetic ) has on the alpha and beta receptors
A1- blood vessels, constriction
A2- Blood vessels, constriction/relaxation
B1- heart, increased HR, increased contractility
B2- blood vessels, relaxation (also relaxes airways)
Describe the full affects of acetylcholine (parasympathetic) has on muscarinic receptors
M2- decreases HR, decreases contractility
What does atropine do
blocks muscarinic receptors, acting as an antagonist for acetylcholine
What does angiotensin II do
increases blood pressure by inducing vasoconstriction
What blocks angiotensin II
Isosaratan
