Which part of the nervous system includes the brain and spinal cord?

The Central Nervous System (CNS) is the primary control center for the body, consisting of both the brain and spinal cord. The brain serves as the processing unit, handling thought, memory, and coordination, while the spinal cord acts as a conduit for signals traveling between the brain and the rest of the body. Together, they facilitate essential functions, including reflexes and higher cognitive processes.

The Peripheral Nervous System (PNS) consists of all the nerves that branch out from the CNS to the rest of the body, connecting muscles and organs to the brain and spinal cord but not including these structures themselves. The Somatic Nervous System is a component of the PNS responsible for voluntary movements and transmitting sensory information, while the Autonomic Nervous System, also a part of the PNS, controls involuntary functions like heart rate and digestion. These systems support the CNS but do not encompass it.

Thus, the correct answer highlights that the CNS is specifically defined by its components, the brain and spinal cord, which are critical to the functionality of the entire nervous system.