What body system primarily regulates metabolic processes through hormone secretion?

• A. Circulatory
• B. Excretory
• C. Nervous
• D. Endocrine

Answer: (D)

The endocrine system is the primary regulator of metabolic processes in the body through the secretion of hormones. Hormones are chemical messengers produced by endocrine glands such as the thyroid, adrenal glands, pancreas, and pituitary gland. These hormones travel through the bloodstream to target organs and tissues, influencing a wide array of physiological processes including metabolism, growth, mood, and immune response.

For instance, insulin, produced by the pancreas, plays a crucial role in regulating blood glucose levels, which is a key aspect of metabolism. Thyroid hormones regulate the metabolic rate of cells, affecting how energy is utilized in the body. The intricate balance and timing of hormone release help to maintain homeostasis, ensuring that the body's metabolic demands are met according to varying conditions.

Other systems, such as the circulatory, excretory, and nervous systems, play important roles in the body but do not primarily regulate metabolic processes through hormones. The circulatory system facilitates the transport of hormones throughout the body, while the excretory system is involved in waste removal and maintaining fluid balance. The nervous system, while it can influence metabolic functions through neurotransmitters, primarily regulates immediate responses to stimuli rather than the long-term metabolic processes controlled by hormones.