Editing Anatomy and Physiology (section)

== Homeostasis and Feedback ==

'''Homeostasis''' is the maintenance of a stable internal environment despite external change. It is maintained mostly by '''negative feedback''', in which a change triggers a response that reverses the change. Rising blood glucose triggers insulin release, glucose falls, and insulin secretion decreases. Falling blood pressure triggers baroreceptor-mediated sympathetic activation, blood pressure rises, and the stimulus is removed.

'''Positive feedback''' amplifies a change until an endpoint is reached. There are few physiologic examples: oxytocin release during labor intensifies contractions until delivery, and the clotting cascade amplifies until a clot forms.

'''Nursing application:''' Compensation is a negative-feedback response, and it hides deterioration. A patient in early compensated shock may have a normal blood pressure because tachycardia and vasoconstriction are holding it up. Rising heart rate, narrowing pulse pressure, cool skin, restlessness, and falling urine output appear before hypotension. Waiting for a low blood pressure to act is waiting too long. This is also why children compensate impressively and then decompensate abruptly.