Facial Expressions-Grammar
The non-manual markers* (NMM) is the accurate description of this parameter because in ASL, this parameter has grammatical application and less related to emotional facial expressions.
This is a feature of ASL that is not written easily (through sI5s, it can be shown). The NMM must be used in the sentences produced along with other parameters. One must have the brows-furrowed WHq (WH family question/statement) when signing YOUR NAME WHAT?
In English, the tone of 'What' is the same as the brow-furrow of WHAT. The only difference is the sound and the sight of the emphasis of "what" in the sentence.
In addition to NMMs, we have mouth morphemes and adverbial grammar, which are not mouthing English words. They are the shaping-movement of the mouth to reflect size, specific signs, and specific expressions tied to grammar.
Examples: CHA, MM, OO, LOOK (tongue repeat movement), CS, HUGE and so on.
*Also known as non-manual signals