Cardiovascular Pharmacology Flashcards
describe sympathetic nerve fibres
sympathetic nerve fibres has a short preganglionic fibre and a long post ganglionic fibre. The preganglionic fibre is myelinated and releases acetylcholine. The post ganglionic fibre is unmyelinated and mostly release noradrenaline.
describe parasympathetiv nerve fibres
parasympathetic nerve fibres have a long preganglionic fibre and a short postganglionic fibre. the preganglionic fibre is myelinated, however the postganglionic fibre is unmyelinated. Both fibres release acetylcholine.
describe innervation to the adrenal medulla:
a myelinated pre-ganglionic fibre releases acetylcholine at the adrenal medulla. This stimulates the release of adrenaline and noradrenaline
What is the affect of parasympathetic innervation on vascular tone
Parasympathetic NS has little affect on vascular tone
Describe the synthesis of Noradrenaline
In the cell cytosol L-tyrosine is converted to L-DOPA and dopamine. dopamine is then actively tranported into storage vesicles where it is converted to noradrenaline
describe the synthesis of adrenaline
Adrenaline is synthesized from noradrenaline in the adrenal medulla.
describe alpha 1 adrenergic receptors
a1 receptors are located postsynaptically. They stimulate Gq which causes the activation of phospolipase C.
a1 receptors on smooth muscle cause contraction (VASOCONSTRICTION)
describe aplha 2 receptors
a2 receptors are located presynaptically. causes the INHIBITION of adenylate cyclase which in turn causes cAMP to decrease. mediated by Gi
(a2 receptors inhibit the release of noradrenaline *-ve feedback)
describe beta 1 receptors
b1 receptors are located postsynaptically. They activate adenylate cyclase and cause increase in cAMP. (this is mediated by Gs)
When b1 receptors are stimulated by adrenaline, this increases the heart rate and force of contraction. (+ve dromotropy and Inotropy)
describe beta 2 receptors
b2 receptors are located postsynaptically. They activate adenylate cyclase and cause an increase in cAMP. (this is mediated by Gs).
b2 receptors on smooth muscle cause relaxation (VASODILATION)
describe beta 3 receptors
b3 located postsynaptically. active adenylate cyclase causing an increase in cAMP. (this is mediated by Gs).
b3 causes lypolysis in fat cells.
when are alpa1 adrenergic antagonists (e.g. Doxazosin) used?
treatment of hypertension
When are beta adrenergic receptor blockers used?
Used in hypertensives to reduce the chronotropic and ionotropic effects of catecholamines. leading to decreased heart rate and myocardial contractility. [*positive chronotropy increases the heart rate by changing the rhythm of the SA node.]
nonselective beta antagonists:
What receptors do they bind to?
Why are they used?
Give an example:
bind equally to b1 and b2 receptors. Used to treat hypertension and angina. e.g. propranolol
nonselective beta and a1 antagonists:
what receptors do they bind to?
Why are they used?
Give an example:
bind to b1/b2 and a1 receptors equally. Used to treat severe hypertension. eg. labetalol
(a1 causes vasodilation)
Partial agonists:
why are they used?
give an example:
Useful to treat bradycardia. e.g.pindolol
b1 selective antagonists:
Why are they used?
give an example drug:
Used to treat hypertension and angina.
e.g. atenolol
how do beta-receptor antagonists help to stabalise angina?
They decrease the sympathetic drive to the heart. this has a negative chronotropic effect (decreases heart rate). Also has a negative ionotropic effect (decreases force of contractions). therefore there is less demand for Oxygen.
Prolongation of diastole (negative chronotropy) results in a longer time for perfusion of the coronary arteries.
Decrease in blood pressure (due to less RAAS activation) decreases work load of heart so less oxygen demand.
what is used to treat variant angina?
calcium channel blockers
Patients with unstable angina, have a high risk of myocardial infarction. what would be their longterm treatment?
Aspirin (anticoagulant), beta blocker (reduce heart rate and oxygen demand), ACE inhibitor (reduce hypertension)
what is the normal blood pressure range?
120-135 / 70-85 mm Hg
what is the blood pressure for hypertension?
> 140/90 mm Hg
what drugs are used to treat supraventricular and ventricular arrhythmias.
Class II antiarrhythmic agents (β-blockers)
name 5 adverse effects of beta blockers
Bronchoconstriction - in asthmatic patients this may be life-threatening
Cardiac failure – patient with heart disease may depend on sympathetic drive to maintain their cardiac output.
Bradycardia – serious bradyarrhythmias in patients with defects in AV conduction
Exacerbation of IHD - abrupt discontinuation of long term treatment may exacerbate angina and increase risk of sudden death
Diabetics
-mask warning signs (palpitations and tremor) of impending hypoglycaemia
-prolong hypoglycaemia (blockade of b2 stimulation of glycogenolysis)
Fatigue – reduced cardiac output and muscle perfusion
Cold extremities – blockade of vasodilatory b2 receptors
CNS effects – sleep disturbances, vivid dreams
