(N/A) In living organisms, the functions of organs and organ systems must be coordinated to maintain homeostasis.
Two or more organs interact and complement each other's functions through the process of coordination. For example, during physical exercise, the rate of respiration, heartbeat, and blood circulation increase. When physical exercise stops, the activities of all these organs gradually return to their normal states.
Thus, during physical exercise, the functions of muscles, lungs, heart, blood vessels, kidneys, and other organs are coordinated.
In humans, all physiological activities are jointly coordinated and regulated by the $Nervous \text{ } System$ and the $Endocrine \text{ } System$.
The structural and functional unit of the nervous system is the $Neuron$.
The neural system provides an organized network for quick coordination, while the endocrine system provides chemical integration through hormones.