In the cardiovascular system, what is the effect of high-dose Atropine on the heart rate?
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Correct answer: Tachycardia due to blockade of M2 receptors at the SA node
Atropine blocks M2 receptors at the sinoatrial (SA) node, which normally mediate the inhibitory 'vagal tone' of the parasympathetic nervous system. Removing this inhibition results in an increase in heart rate.
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