What is the physical and mental responses of marijuana?

Hallucinogenics typically affect respiratory(breathing) and heart (pulse).

These types of drugs are harmful in short term use (recreational) and long term use (addiction)

mental responses tend to vary with each hallucinogen but if you are talking about the actual brains response then it is classified as physiological.

Physiologically a persons brain will go haywire after long term use, producing less or more of chemicals which are produced regularly, producing the wrong chemicals at wrong times, interfering with sleep, eating, eventually through long term use the heart and lungs start to suffer as well, because it becomes increasingly harder to function under the influence of these drugs, typically ending in Cardiac Arrest or Respiratory Failure.