Some time ago Giovanni Lussu pointed out an article to me: “pages 47-66 [ Typographica 12], entitled Emphatic fist, informative arrow, with a short text by Edward Wright commenting some pictures by Herbert Spencer of fists (…) and arrows (…).
The article ends this way: “The sign on the highways is really not an arrow at all; it is a diagram which can change direction and be read from a distance at windscreen level. We can call them arrows because ‘arrow’ now means a certain kind of sign”.
1. There are several pointer of sense AND direction (such as fists or aztec footprints (meaning also “movement” or showing a sequence) or even medieval phylakterion);
2. and arrow is used not only to point a “sense” but also to show a sort of hierarchy in the synsemic text (for exemple, on one side of the arrow there is the main text on the other the “explanation”, or the “note”) or simply to “point out” something in the text.