. Compare and contrast the CNS with the PNS. What are 4 structural differences? Hypothesize how these structural differences translate into functional differences between the two systems. (2 points) Structural Difference Functional Difference
The Correct Answer and Explanation is:
Here’s a completed comparison table followed by an explanation that expands on the differences:
| Structural Difference | Functional Difference |
|---|---|
| CNS includes the brain and spinal cord; PNS includes all nerves outside the CNS | CNS processes and integrates information; PNS transmits signals to and from the CNS |
| CNS is enclosed by protective bones (skull and vertebrae); PNS lacks such protection | CNS is shielded from mechanical injury; PNS is more exposed and vulnerable to trauma |
| CNS contains oligodendrocytes for myelin production; PNS uses Schwann cells | CNS myelinates multiple axons efficiently; PNS myelinates one axon per Schwann cell |
| CNS primarily consists of neuronal cell bodies; PNS mainly contains axons and ganglia | CNS supports high-level computation; PNS relays sensory and motor signals |
Explanation:
The central nervous system (CNS) and peripheral nervous system (PNS) work together to coordinate body function, but they differ structurally and functionally. The CNS consists of the brain and spinal cord, which serve as the control center for interpreting sensory data and issuing commands. In contrast, the PNS is composed of nerves and ganglia branching off from the spinal cord and brainstem. These structures carry information between the CNS and the rest of the body, facilitating communication with muscles, glands, and sensory organs.
Structurally, the CNS is encased in protective bone—specifically the skull and vertebral column—which guards it against mechanical trauma. The PNS, however, lacks this level of physical protection, making peripheral nerves more susceptible to external injury. On the microscopic level, different cells carry out myelination: oligodendrocytes in the CNS and Schwann cells in the PNS. This distinction affects the efficiency of signal conduction. Oligodendrocytes can myelinate multiple axons at once, whereas Schwann cells can only wrap around a single axon, potentially limiting conduction speed in the PNS.
Functionally, these differences support the systems’ distinct roles. The CNS is optimized for high-level processing, with many tightly packed neuronal cell bodies enabling complex computations. The PNS, with its long axons and ganglia, acts primarily as a communication network—routing sensory inputs to the CNS and relaying motor outputs to the body. Together, they form an integrated and responsive control system.
