<prompt> Chemoreceptors operate between pressure range of:Below 90 mm HG40-100 mm Hg70-150 mm Hg70-220 mm Hg  <response>: 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. 