What does the release of epinephrine by the adrenal medulla into the bloodstream exemplify?

The release of epinephrine by the adrenal medulla into the bloodstream exemplifies endocrine control because it involves the secretion of hormones directly into the bloodstream to regulate physiological processes. The adrenal medulla, a part of the adrenal glands located above the kidneys, functions as an endocrine organ by synthesizing and releasing epinephrine (also known as adrenaline) in response to stress or stimulation from the nervous system.

Once released into the blood, epinephrine acts on various target organs, leading to effects such as increased heart rate, elevated blood pressure, and enhanced energy availability. This systemic action, characterized by the hormone's ability to travel through the circulation and influence distant tissues, is a hallmark of endocrine control.

In contrast, exocrine control involves the secretion of substances through ducts to specific sites, neural control refers to the direct influence of the nervous system on target tissues via neurotransmitters, and positive feedback describes a mechanism that amplifies responses in a biological system rather than initiating hormone release as in this case. Therefore, the correct answer highlights the role of hormones and the endocrine system in coordinating body responses.