Briefly describe the organization of the central nervous system. Describe the function and circulation of cerebrospinal fluid. What is meant by the following terms: upper motor neuron lesion, lower...

Briefly describe the organization of the central nervous system. Describe the function and circulation of cerebrospinal fluid. What is meant by the following terms: upper motor neuron lesion, lower motor neuron lesion, flaccid paralysis, and spastic paralysis?