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The endocrine system is responsible for regulating various body activities through the release of hormones. Hormones are chemical messengers that travel through the bloodstream to specific organs and tissues, where they induce a variety of physiological responses. This system plays a crucial role in maintaining homeostasis, controlling growth and development, managing metabolism, and coordinating reproductive processes, among other functions.

In contrast, the nervous system primarily regulates body activities through electrical signals and neurotransmitters, facilitating rapid responses to stimuli. The muscular system is responsible for movement and maintaining posture but does not regulate bodily functions through hormones. Lastly, the skeletal system provides structural support and protection for the body but does not have a role in hormone release or regulation. Thus, the endocrine system is the key player in the hormonal regulation of bodily activities.