What part of the bran is associated with regulating heart rate, breathing, and salivation?

Medulla Oblongota is the part of the brain which is associated with regulating heart rate, breathing, and salivation. It is most commonly referred to as medulla.
The medulla  is the lowest part of the brain and the lowest portion of the brainstem. It adjusts force and rate of heart contraction, adjusts blood vessel diameter for bp, generate respiratory rhythm, rate and depth of breathing (w/pons) and is responsible for other autonomic functions.

Major sources of stress, such as a death or divorce, problems in family relationships, job loss, school, and substance abuse, can trigger or aggravate some mental disorders in some people. but not everyone who goes through those things develops a mental illness