This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Heart, Circulation, and Blood, Subject name: Physiology
[{'content': "'Y' descent of the IVP is due to: \nSelect and explain. \nA. Atrial relaxation, B. Closure of the right ventricle, C. Opening of the triscuspid valve, D. Opening of the left ventricle", 'role': 'user'}, {'content': 'Answer: C \nExplanation: (Opening of the tricuspid valve): Ref: 1306-H, 569-G (1384-HI7th) (512- Ganong 23rd)Jugular venous pulse: (JVP)* Positive presystole \'a wave\' is produced by venous distension due to right atrial contraction and is the dominant wave in the JVP.* Large \'a wave\' indicates that the right atrium is contracting against an increased resistance (Tricuspid stenosis, pulmonary hypertension or PS)* Large \'a-wave\' also occurs during arrhythmias whenever the right atrium contracts while the tricuspid valve is closed by right ventricular systole.* C-wave - produced by the bulging of the tricuspid valve into the right atrium during right ventricular isovolumetric systole and by the impact of the carotid artery adjacent to the jugular vein* "X-descent" is due to both to atrial relaxation and to the downward displacement of the tricuspid valve during ventricular systole* "V wave" results from the increasing volume of blood in the right atrium during ventricular systole when the tricuspid valve is closed.* "Y descent" produced mainly by the opening of the tricuspid valve and the subsequent rapid inflow of blood in the right ventricles. (Tricuspid regurgitation)', 'role': 'assistant'}]