This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
[{'content': 'Impulses from SA node to the left atrium and AV node passes through: \nSelect and explain. \nA. Bundle of His, B. Bachmann bundle, C. Purkinje fibres, D. None', 'role': 'user'}, {'content': 'Answer: B \nExplanation: There are three bundles of atrial fibers that contain Purkinje-type fibers and connect the SA node to the AV node: the anterior, middle (tract of Wenckebach), and posterior (tract of Thorel) tracts.\nBachmann bundle is sometimes used to identify a branch of the anterior internodal tract that connects the right and left atria.\xa0\n\xa0\nKey Concept\n3 INTERNODAL TRACTS:\nConnects SA node to AV node:\n\nAnterior – Bachman’s bundle\nMiddle – Wenckebach’s bundle\nPosterior – Thorel’s bundle\n\nReference: Ganong’s Review of Medical Physiology T W E N T Y - F I F T H\xa0 \xa0E D I T I O N page no 519', 'role': 'assistant'}]