How do feedback loops in the nervous/endocrine system regulate body conditions?

there are both positive and negative feedback loops.

an example of a positive feedback loop is the one used for childbirth. the brain secretes oxytocin, which stimulates contractions. more and more oxytocin is secreted, contractions increase in frequency, and this continues until the child is born.

negative feedback loops are more common. one example is with insulin. when there is a lot of sugar in your blood, the brain sends signals to the pancreas to secrete insulin. insulin tells the body to use the circulating sugar either as energy or to store it for future use. as blood sugar decreases, the brain tells the pancreas to stop secreting insulin so that blood sugar doesn't get too low.

In positive feedback loops, the result/response enhances the stimulus so that there is more result/response. These are not common in the human body so they usually control infrequent events. However, in terms of the nervous system, positive feedback is responsible for the depolarizing phase of action potentials. Increased sodium permeability due to increased channel openings leads to greater depolarization, which lead to increased sodium permeability, and the cycle continues.

Negative feedback loops comprise of most of the homeostatic control mechanisms. In negative feedback loops, the output shuts off the original effect of the stimulus or reduces its intensity.