What receptors in the lung, when stimulated, produce broncho constriction and which produce broncho dilation? 2. What happens to FEV1, BP and HR when M3 receptor agonist is administered and why?

The main function of the respiratory system is gas exchange (O2 and CO2). Ventilation is the movement of air through the respiratory tract into (inspiration) and out of (expiration) the respiratory zone (lungs).