Which of the following is NOT a major sense organ of the body?

The brain is not classified as a major sense organ; instead, it acts as the processing center for sensory information received from the sense organs. The primary sense organs include the skin, which detects touch, temperature, and pain; the eyes, which are responsible for vision; and the ears, which facilitate hearing and balance.

The skin contains nerve endings that respond to various stimuli, the eye contains photoreceptors for light detection, and the ear has structures that respond to sound waves and help maintain balance. While the brain is critical for interpreting the information from these sensory inputs and coordinating responses, it does not directly sense external stimuli itself. This distinction is essential in understanding the roles of different systems in the body related to sensory perception.