This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Physiology
[{'content': 'Occlusion of common carotid aeries on both sides leads to \nSelect and explain. \nA. Increase in hea rate and BP, B. Increase in BP and decrease in hea rate, C. Decrease in hea rate and BP, D. No effect on hea rate and BP', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Occlusion of both common carotid aeries causes an increase in HR and BP. Reduced sinus pressure - response carried to nucleus tractus solitarius glossopharyngeal and vagus nerve -less inhibitory effect on the vasomotor center. Decreased parasympathetic activity to the hea- increases hea rate. Increased sympathetic activity to the hea and blood vessels - increases hea rate, contractility, constricts aerioles - increases TPR, constricts veins- increases venous return. The carotid baroreceptors are located in the walls of the carotid sinus, which is located at or slightly above the bifurcation of the common carotid aeries. So, the occlusion of common carotid aeries is occlusion proximal to the carotid sinus. If the occlusion is distal to the carotid sinus -increase in sinus pressure - activation of baroreceptor reflex- decrease in BP and HR. Ref: Guyton and Hall 13th edition Pgno: 166', 'role': 'assistant'}]