A recent r.h.f post reminded me of this... I don't think this originates with him, but a psychology professor of mine used to say something like the following in the neuropsychology section of his intro course: The hypothalamus is one of the most important parts of the brain, involved in many kinds of motivation, among other functions. The hypothalamus controls the "Four F's": 1. fighting; 2. fleeing; 3. feeding; and 4. mating.
(From the "Rest" of RHF)