in living organisms what are the 2 most basic strategies for promoting survival? how does each strategy seek to achieve its aim? which one has the higher priority in the “long term and why, and which one has the higher priority in the “short term and why? what 3 types of detectors are necessary? what general kind of purposive behavior is involved? What functions does each serve singly and together? what does the VTA-nucleus-accumbens medical forebrain bundle circuit play?