Answer:
To create a model of the central nervous system, you would need to add the spinal cord to your brain model. The spinal cord is a long, thin, tubular bundle of nervous tissue that extends from the brainstem to the lower back and is responsible for transmitting signals between the brain and the rest of the body. By adding the spinal cord to your brain model, you would create a model of the central nervous system that includes both the brain and spinal cord, and their integration and regulation of the body's many functions.
You would connect the spinal cord to the brainstem in your model of the central nervous system. The brainstem is the lower part of the brain that is continuous with the spinal cord and is responsible for many vital functions, such as breathing, heart rate, and blood pressure, and is also involved in the transmission of sensory and motor signals between the brain and the body. By connecting the spinal cord to the brainstem in your model, you would establish the important link between the brain and the rest of the body.