Final answer:
A physiological parameter regulated by varying signal intensity is under negative feedback control, essential in maintaining homeostasis by reversing deviations from the set point.
Step-by-step explanation:
A physiological parameter which is regulated in an up-down fashion by signals that are always present but change in intensity is said to be under negative feedback control.
Maintaining homeostasis requires that the body continuously monitor its internal conditions, such as body temperature and blood pressure, and react to deviations using negative feedback mechanisms. For example, when the set point of body temperature is exceeded, physiological processes are activated to bring the temperature back within the normal range.
Control centers in the brain and other parts of the body monitor various parameters and instigate a response to steer a deviating condition back to its set point. This is achieved by negative feedback loops, which act to reverse changes to the conditions, maintaining body parameters within their normal range. Positive feedback loops, in contrast, are much less frequent and act to intensify the response until an endpoint is reached.