Two students, Vineet and Kamlesh were asked to demonstrate in dogs the role of sinus nerve in hypo-volemic shock. Vineet severed the sinus nerve when the mean blood pressure (MBP) was 85 mm Hg and Kamlesh cut the sinus nerve when the mean blood pressure was 60 mm Hg. On cutting the sinus nerve

C i.e. Both recorded an increase in MBPWhen carotid sinus nerve is sectionedLoss of inhibitory impulse from carotid sinus nerve --> Medullary vasomotor center activated -* 1' sympathetic discharge -> Vasoconstriction ( TBP), IHR & T CO.The baroreceptors do not fire when mean BP is below 30 mm Hg (fire maximally at mean BP of 150 mm Hg) Carotid sinus nerve and vagal fibres from aoic arch commonly called Buffer nerves.* Severing only carotid sinus nerve will not lead to decrease in BP because aoic arch baroreceptors are still functional. If both are severed the BP rise to more than 200-300 mm Hg.