Explain the difference between positive and negative feedback mechanisms and use examples that are easy to understand for non-biologists, such as valves releasing steam in a pipe, ovens pre-heating to certain temperatures, and so on.

Mrs. h, age 42 years, is experiencing severe rheumatoid arthritis in her wrists, fingers, and knees. the joints are quite inflamed, red, and swollen. she is sitting rigidly in a chair and refuses to put on a sweater, even though she is shivering, or let anyone touch her arms. she has been prescribed an analgesic and an anti-inflammatory drug, but her dose is not due for another hour. she is feeling nauseated, so she has not eaten for the past 8 hours. based on patient history and the signs and symptoms, discuss how the effects of pain are exacerbating her condition.