The nervous system performs the function of integrating the sensory information and then responding to the sensory information.
This function is especially performed by the central nervous system where the thalamus part of the brain is normally associated with the sensory neurons as they have nuclei which sense and analyse the information.
If the organism will not have the neurons which could perform the function of integration mainly the centers associated with sensing and analysing therefore, the organism will lose its capability to interpret or analyse the stimuli.
Cellular respiration is when cells take oxygen and food to make energy, and also water and carbon dioxide. For the organism to get oxygen, they breath in the air from the outside. The oxygen travels through the respiratory pathway to get to cells.