What process describes a gland's secretion being regulated by the levels of substances in the bloodstream?

The concept of a gland's secretion being regulated by the levels of substances in the bloodstream is primarily characterized by a feedback mechanism. In biological systems, feedback mechanisms play a crucial role in maintaining homeostasis, which is the balance of physiological processes.

In this context, feedback mechanisms can be classified as either positive or negative. Negative feedback is the more common type, where the secretion of a hormone or substance is decreased in response to high levels of a particular substance in the bloodstream, thus working to restore balance. For instance, if blood sugar levels rise, the pancreas secretes insulin to help lower those levels. Conversely, when blood sugar levels drop, insulin secretion decreases.

This dynamic allows the body to continuously monitor and adjust physiological responses, ensuring that internal conditions remain stable despite changes in the external environment. While homeostatic control generally encompasses the overall process of maintaining stable internal conditions, it is the feedback mechanisms that specifically detail how individual glands adjust their secretions based on substance levels in the blood, making feedback mechanism the most accurate answer in this scenario.