Which organ is primarily responsible for controlling all body functions?

The brain is the primary organ responsible for controlling all body functions. It serves as the central processing unit of the nervous system, coordinating both voluntary actions, such as movement and speech, and involuntary actions, such as breathing and digestion. The brain interprets sensory information from the environment and sends signals to the body to elicit appropriate responses. It is also involved in higher functions such as reasoning, emotions, and memory.

Additionally, the brain plays a crucial role in maintaining homeostasis, which is the body's way of keeping its internal environment stable despite external changes. It regulates vital processes by communicating with various organs and systems through the nervous system and hormonal signals, thereby ensuring that all bodily functions are harmoniously integrated and efficient.