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': "While measuring jugular venous pressure, 'a' wave is indicative of: \nSelect and explain. \nA. Atrial filling, B. Atrial relaxation, C. Atrial contraction, D. Ventricular relaxation", 'role': 'user'}, {'content': "Answer: C \nExplanation: The pressure pulsations that occur in the right atrium are transmitted in retrograde fashion to the large veins near the hea. Atrial contraction produces the first pressure peak called the a wave. The c wave is the transmitted manifestation of the rise in atrial pressure produced by the bulging of the tricuspid valve into the atria during isovolumetric ventricular contraction. The v wave mirrors the rise in atrial pressure before the tricuspid valve opens during diastole. Ref: Barrett K.E., Barman S.M., Boitano S., Brooks H.L. (2012). Chapter 30. The Hea as a Pump. In K.E. Barrett, S.M. Barman, S. Boitano, H.L. Brooks (Eds), Ganong's Review of Medical Physiology, 24e.", 'role': 'assistant'}]