Science has made huge strides in understanding the human brain and how it functions. For example, we know that the frontal lobes are the center of rational thinking and of self control. ... Lesions or damage to the frontal lobes and to other parts of the brain can and affect impulses and impulsive behaviors.
Olfactory sensory neurons in the epithelium detect odor molecules dissolved in the mucus and transmit information about the odor to the brain in a process called sensory transduction
A becuaase you breathe in oxygen and you release carbon dioxide.