Närvikiududel

Närvikiududel, also known as nerve fibers, are the long, slender projections of nerve cells (neurons) that transmit electrical signals. These signals, called nerve impulses or action potentials, are the fundamental means of communication within the nervous system. A typical nerve fiber consists of an axon, which is the main conducting part, and often a myelin sheath, which is an insulating layer that speeds up impulse transmission.

There are two main types of nerve fibers: myelinated and unmyelinated. Myelinated fibers are covered by a myelin sheath, which is produced by glial cells (Schwann cells in the peripheral nervous system and oligodendrocytes in the central nervous system). This sheath is interrupted at regular intervals by gaps called nodes of Ranvier. The impulse jumps from one node to the next, a process called saltatory conduction, significantly increasing the speed of transmission. Unmyelinated fibers lack this insulating sheath and transmit impulses more slowly through continuous conduction along the axon membrane.

Nerve fibers are classified based on their diameter and conduction velocity. Larger diameter fibers generally conduct impulses faster than smaller diameter fibers. This classification is important for understanding the different roles nerve fibers play in sensory perception, motor control, and autonomic functions. For instance, motor neurons that control voluntary muscles have large, myelinated axons for rapid responses, while sensory fibers carrying dull pain signals may be thin and unmyelinated. The integrity and function of nerve fibers are crucial for the proper functioning of the entire nervous system, and damage to them can lead to various neurological disorders.