In human anatomy, what does the central nervous system consist of?

Introduction / Context:
The nervous system in humans is broadly divided into the central nervous system and the peripheral nervous system. Knowing which structures belong to each division is fundamental for understanding how the body processes information and controls movement. This question asks you to identify what the central nervous system includes according to standard anatomical classification.

Given Data / Assumptions:

The nervous system has central and peripheral parts.
Key structures are the brain, spinal cord, and peripheral nerves.
We use common textbook definitions for these divisions.

Concept / Approach:
The central nervous system, often abbreviated as CNS, consists of the brain and the spinal cord only. These structures are enclosed within bone for protection, with the brain inside the skull and the spinal cord inside the vertebral column. The peripheral nervous system includes cranial nerves, spinal nerves, and their branches that extend out into the body to connect the CNS with muscles, glands, and sensory receptors. When a question asks specifically about the central nervous system, peripheral nerves must be excluded from the answer.

Step-by-Step Solution:
Step 1: Recall that the CNS is made up of the brain and spinal cord as the main integration and processing centers. Step 2: Recognize that peripheral nerves form the peripheral nervous system, not the central nervous system. Step 3: Review the options and find the one that lists brain and spinal cord together without including peripheral nerves. Step 4: Select brain and spinal cord as the correct description of the central nervous system.

Verification / Alternative check:
In diagrams, the central nervous system is often highlighted in one color within the midline of the body, showing only the brain and spinal cord. Nerves radiating outwards in another color are labeled as peripheral. Medical terms such as central nervous system disorders or injuries refer to conditions affecting the brain or spinal cord, further confirming that these two structures define the CNS.

Why Other Options Are Wrong:
Brain and all peripheral nerves: This mixes central and peripheral parts and does not match the strict definition of CNS.
Spinal cord and all peripheral nerves: This also incorrectly includes peripheral nerves instead of the brain.
Brain, spinal cord, and all peripheral nerves: This describes the entire nervous system, not specifically the central nervous system.

Common Pitfalls:
A common error is to group all nervous tissue together without distinguishing central from peripheral divisions. Another pitfall is thinking that cranial nerves are part of the central nervous system simply because they originate near the brain. In fact, cranial and spinal nerves are classified as peripheral. Always remember that central refers strictly to brain and spinal cord.

Final Answer:
The central nervous system consists of the brain and spinal cord only.