A highway for nerve impulses moving between the brain and the spinal cord and where nerve tracts cross
controls the autonomic nervous system, cardiovascular system, and digestive
system, and regulates water balance, temperature, appetite, sleep, sexual desire,
and emotions
the center of thought, Judgment, memory, language, and problem solving
coordinates voluntary body movements and maintains equilibrium and balance
provide a protective covering to the structures of the central nervous system to
cushion the brain and spinal cord

An epidemic is a large and localized outbreak of a sickness or disease.  a pandemic is a large global outbreak of a sickness or disease. 

explanation:

two years ago, when picking flowers in the mountains back of yosemite valley, i found a book. it was blotted and storm-beaten; all of its outer pages were mealy and crumbly. the paper seemed to dissolve like the snow beneath which it had been buried, however; many of the inner pages were well preserved. and although all were more or less stained and torn, whole chapters were easily readable. this is the condition of the great open book of yosemite glaciers today; its granite pages have been torn and blurred by the same storms that wasted the castaway book.two years ago, when picking flowers in the mountains back of yosemite valley; i found a book. it was blotted and storm-beaten, all of its outer pages were mealy and crumbly. the paper seemed to dissolve like the snow beneath which it had been buried, however, many of the inner pages were well preserved. and although all were more or less stained and torn; whole chapters were easily readable. this is the condition of the great open book of yosemite glaciers today, its granite pages have been torn and blurred by the same storms that wasted the castaway book.