Living Will is a term that may be more appropriate in public culture, and perhaps in states other than Michigan. There are no specific Michigan statutes dealing with something called a "living will".
When it comes to setting up the decision-making process, for how health care decisions are made, and who makes them, the gold standard is a properly drafted Medical Power of Attorney (aka a Durable Power of Attorney for Health Care). In a properly drafted Medical Power of Attorney, it will be clear who the initial agent is, who will carry out the principal's wishes; it will be clear who the successor agents are; religious and other preferences can be set forth in the document, as to how extensive the measures should be, to prolong life; and finally, a properly drawn Medical Power of Attorney will help establish procedures for the resolution of disputed medical care decisions.
A properly drafted Medical Power of Attorney can also provide needed guidance to doctors & nurses, hospitals, nursing homes, hospice organizations and the like, for how best to provide care for a now-incapacitated person.