Answer to Question 1
There are several layers of defense that comprise our protective and immune systems. The first layer consists of our skin and mucous membranes. Most bacteria or viruses we contact are blocked by the skin from mounting an invasion. Those that manage to penetrate the skin are vigorously attacked. Bacteria that penetrate the skin are ingested by white blood cells otherwise known as leukocytes.
Answer to Question 2
Solomon and Moos were the first to publish the term psychoneuroimmunolo gy (PNI) to refer to the study of the relationship between the psychological, neurological, and immunological interactions. Their introduction of the term was followed over a decade later by stress researcher Kenneth Pelletier popularizing the idea in his 1977 book Mind as Healer, Mind as Slayer. Pelletier and Herzing defined the then emerging interdisciplinary field of PNI as the study of the intricate interaction of consciousness (psycho), brain and central nervous system (neuro), and the body's defense against external infection and internal aberrant cell division (immunology).
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