What does this regulation of body activities, such as response to internal and external stimuli and communication between parts of the body

Regulation of body activities such as response to internal and external stimuli and communication between parts of the body is carried out by the NERVOUS SYSTEM.
The nervous system is made up of network of nerves which transmit information from one part of the body to the other. The major components of the central nervous system are the brain and the spinal cord which work together to relay information to different body parts.