What is the primary function of the endocrine system?

The primary function of the endocrine system is to produce and secrete hormones, which are chemical messengers that play crucial roles in regulating various physiological processes throughout the body. These hormones are secreted directly into the bloodstream and can affect distant target organs or tissues, influencing functions such as metabolism, growth and development, tissue function, and mood regulation.

Unlike the nervous system, which offers rapid and short-term responses to stimuli, the endocrine system typically operates over longer durations, providing a more sustained influence on the body's activities. For example, hormones like insulin regulate blood glucose levels, while others like cortisol are involved in stress response and metabolism.

The other choices pertain to distinct systems or functions not primarily associated with the endocrine system. Muscle movements are controlled by the muscular system under the influence of the nervous system, gas exchange occurs primarily in the respiratory system, and temperature regulation involves multiple systems, including the integumentary system and hypothalamus. Each of these systems has a specialized role, but the fundamental purpose of the endocrine system centers on hormone production and secretion.