What is the difference between the heart (qalb), the mind/intellect (fu'ad), and the reason/intellect (aql or lubb) in light of the Sharia texts?

The heart (qalb) is so named because of its frequent changes (taqallub). It is used to refer to the spirit (ruh), knowledge (ilm), and courage (shajaah). The mind/intellect (fu'ad) is the heart, with the added connotation of ignition or fervor (tawaqqud) within it. The intellect (aql) is the faculty by which a human being distinguishes and comprehends. The core/essence (lubb) is the intellect purified from impurities. These terms have similar meanings, with subtle differences between them.