Josh notices that the frog he is dissecting has many different types of tissues and cells. The cells are different due to different gene expression. The term differential gene expression denotes the activation of different genes within a cell. Each cell expresses only those genes which it needs.
The main difference between physical and mental health is that our emotions, our ability to work and our relationships are the main things to be influenced by our mental health. When our mental health is positive we can cope with ups and downs. Our mood is stable and we feel optimistic.