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
Chemoreceptors operate between pressure range of: 
Select and explain. 
A. Below 90 mm HG, B. 40-100 mm Hg, C. 70-150 mm Hg, D. 70-220 mm Hg
B: 40-100 mm Hg
Answer: B: 40-100 mm Hg 
Explanation: In nervous circulatory mechanism of aerial BP the chemoreceptor reflex operates between 40-100 mm Hg . Fallen the aerial BP less than 80 mmhg decreases blood flow to the tissues this decreases pO2 2 carotid and aoic bodies and causes stimulation of VMC and CVC and respiratory centre.