Nervbanor

Nervbanor are bundles of axons that transmit neural signals between different parts of the nervous system. In the central nervous system they consist of axons organized into white matter tracts within the brain and spinal cord, while in the peripheral nervous system similar bundles are grouped into nerves that connect to peripheral targets.

The term encompasses both ascending pathways that convey sensory information to the brain and descending pathways that deliver motor commands from the brain to muscles, as well as autonomic pathways that regulate visceral function.

Structure and composition: nervbanor are composed of long-range axons, their myelin sheaths, and supporting glial cells. They are organized into fascicles or tracts with characteristic trajectories; some tracts cross the midline (decussate) at various levels during development.

Examples of major nervous tracts include the corticospinal tract (voluntary motor control), dorsal columns (fine touch and proprioception), spinothalamic tract (pain and temperature), and spinocerebellar tracts (unconscious proprioception). Peripheral nerves bundle sensory, motor, and autonomic fibers for specific regions.

Development and plasticity: nervbanor form during embryogenesis under molecular guidance cues such as netrins and semaphorins that direct axon growth. After injury, certain tracts can reorganize and remyelinate to varying degrees, depending on species and age.

Clinical relevance and imaging: damage to nervbanor produces selective deficits depending on the tract affected, including weakness, numbness, or coordination problems. Diffusion tensor imaging (DTI) and tractography are key noninvasive methods to visualize major white-matter nervbanor in vivo.