Which of the following distinguishes the central nervous system?

The central nervous system (CNS) is specifically defined as comprising the brain and spinal cord. This distinction is crucial because the CNS serves as the primary control center for processing information and coordinating actions throughout the body. The brain interprets sensory input, makes decisions, and sends instructions, while the spinal cord serves as a communication pathway between the brain and the rest of the body.

Other elements listed, such as sensory receptors, primarily belong to the peripheral nervous system, which facilitates the transmission of sensory information to the CNS. The connection between limbs and the nervous system is also a function of the peripheral nervous system, where nerves extend from the spinal cord to various parts of the body. Finally, while the CNS does play a significant role in regulating functions such as heartbeat, this function is more closely associated with the autonomic nervous system, which operates mainly outside of conscious control. Thus, option A accurately encapsulates the specific anatomical components that define the central nervous system.