I always knew Morphine reduced the oxygen demand on the heart, but I never knew through what mechanism. An instructor said that it is done by decreasing the pain so the patient isn't breathing as hard. However, Morphine releases histamine so does that mean it also vasodilates? I know it can affect your hemodynamic state by decreasing your bp and o2 but is that how? I love patho so I am constantly trying to put all the pieces together instead of just knowing the results. Thanks in advance.