What function do sensory neurons serve?

Sensory neurons play a crucial role in the nervous system by carrying incoming information from sensory receptors to the brain or spinal cord. This process is essential for perception, as sensory neurons translate external stimuli—such as light, sound, touch, taste, and smell—into electrical signals that the central nervous system can understand and interpret.

By transmitting this information quickly and efficiently, sensory neurons enable the body to respond to its environment, facilitating both reflex actions and conscious perceptions. For instance, when you touch something hot, sensory neurons send immediate signals to your spinal cord, prompting a quick withdrawal response before the information even reaches your brain, which is pivotal for survival.

The other options do not accurately describe the main function of sensory neurons. While relaying messages to muscles or carrying information to them are functions associated more with motor neurons, and communication between internal brain structures pertains to interneurons, it is the primary role of sensory neurons to channel information from the body's sensory receptors to the brain or spinal cord, making option D the clear and correct choice.