Question

Because they control many cell activities - as well as being controlled by feedback mechanisms - what substances are very important for homeostasis?

Answer 1

hormones

Hormones control many cell activities, so they are very important for homeostasis. But what controls the hormones themselves? Most hormones are regulated by feedback mechanisms. A feedback mechanism is a loop in which a product feeds back to control its own production. Most hormone feedback mechanisms involve negative feedback loops . Negative feedback keeps the concentration of a hormone within a narrow range.