The sense in which we here speak of the heart are in those of first most emotions, and as such are much controlled by our bodys in general rather then our minds. But as mentioned by others, emotions are also a state of the mind, and of the body and can as of such be determined by thought or experience where the mind is the catalyst to spring through emotion or desires, stated by our heart which can in a sense be seen as a path to the subconcious where a maybe "true" self can found.
But with out the relfection of the body, a mind is nothing more then logic, and cold though. As such is the state of the heart can be seen as instinct - affliction for another, emotion and reaction with out pondering thought.
Then the question brings in; which is the stronger?
For humans this might be found in our selfs, as personallity.The set of the "true" self, a revelation is of a clear mind and a clear heart. But this is something that one need to seek for oneself, by belife in ones heart and admist the thoughts. A human stands in the middle - instinctes, emotion, desire, belife - thought, reson, logic, determination
But by looking at nature you can se how the heart is the ruler, stating the path of the mind...
So by now this should sound like preching... Well, by thinking of the clarity in mind by 01:25 in the morning, not to mention that my eyes keep going out of focus you'll have to see it by your self if ther's anything sensible in there... I think so, but no that clear on that part.^^