Various biological and physiological properties of living tissues can be studied by means of NMR techniques. However, the basic physics of extracting the relevant information from the solution of Bloch NMR equations to accurately monitor the clinical state of biological systems is still not fully understood. Presently, there are no simple closed solutions known to the Bloch equations for a general RF excitation. Therefore, an exponential type of solution of the equations presented in this study, which can be taken as definitions of new functions to be studied in detail, may reveal very...