Atropine Cardio-action !

Atropine Functions as a Cardioaccelerator  , so it’s used for treatment of Bradycardia

How is that  ??

Before Atropine administration  :

When the neurotransmitter acetylcholine is released , it binds to cholinergic receptors causing a vagal stimulation

the vagus nerve acts on the sinoatrial (SA) node  and the atrioventricular (AV) node found in the Heart ,

and causes inhibition of the electrical conduction between the two Nodes ( SA & AV )

>> this causes the heart rate to slow down into :

Lub-dub . . . Lub-dub . . .  Lub-dub !!

After Atropine administration  :

Atropine act as a cholinergic blocking drug, so it competes with acetylcholine for cholinergic receptor sites on the SA and AV nodes.

and By blocking acetylcholine ;

– the Vagus nerve stimulation is decreased

– Conduction between the heart nodes ( SA & AV ) is enhanced ( less inhibited )

> > > > > This speeds up the heart rate into :

Lub-dub  Lub-dub  Lub-dub  Lub-dub  Lub-dub !!

~ . ~ . ~ . ~. ~. ~ . ~ . ~ . ~ . ~ . ~

Atropine also may be given to prevent cardiac arrest resulting from vagal reflex activation, incident to anesthetic induction , gastric lavage , or endoscopic procedures .

Ipratropium is used in bradycardia and AV-block to raise heart rate and to facilitate cardiac impulse conduction.

As it is a quaternary substance, it doesn’t penetrate into the brain,
which greatly reduces the risk of CNS disturbances caused by Atropine .

but relatively , high oral doses are required because of an inefficient intestinal absorption.

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Hint :

A healthy heart makes a ” Lub–dub”  sound with each beat.

This sound comes from the valves shutting on the blood inside the heart.

The first sound ” Lub ” happens when the mitral and tricuspid valves close after the blood has been pushed from atria into ventricles ,

while the next sound “ dub ” happens when the aortic and pulmonary valves close after the blood has been squeezed out of the heart .

you can listen to a sample of normal heart sounds in this animation :

Next time you go play with a stethoscope , try to listen to Your own lub-dub 😉

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References :

– Basic and clinical Pharmacology \\ chapter 8

– Color Atlas of Pharmacology

– Pharmacology – 4th edition

– introductory to clinical Pharmacology – 7th edition