Which system is extensive and composed of nerve fibers?

The nervous system is indeed extensive and composed of nerve fibers, which include both neurons and supporting cells. This system is responsible for transmitting signals throughout the body, facilitating communication between the brain and the rest of the body. It is divided into two main parts: the central nervous system (CNS), which comprises the brain and spinal cord, and the peripheral nervous system (PNS), which consists of all other neural elements.

The fundamental role of the nervous system involves sensory input, central processing, and motor output, making it crucial for responding to environmental changes and integrating bodily functions. Its complexity is highlighted by the vast number of connections formed by nerve fibers, allowing for rapid signal transmission and coordination of bodily activities.

In contrast, the cardiovascular system is primarily responsible for transporting blood, oxygen, and nutrients throughout the body. The endocrine system governs hormone release for regulating various bodily functions but does not entail a network of nerve fibers. The musculoskeletal system facilitates movement and provides structure to the body, but its composition focuses more on bones and muscles rather than nerve fibers. Thus, the description of the nervous system aligns perfectly with the characteristics presented in the question.