nervernes

Nervernes is the term used to describe the nerves of the nervous system in many Nordic languages. In humans and other vertebrates, nerves are organized cables that connect the central nervous system to muscles, skin, and internal organs. They enable sensory perception, motor control, and autonomic regulation, coordinating bodily responses to internal and external conditions.

Nerves consist of bundles of axons, termed nerve fibers, which are enveloped by layered connective tissue. The innermost layer, the endoneurium, surrounds individual fibers; groups of fibers form fascicles encased by the perineurium; the outermost layer, the epineurium, surrounds the entire nerve. In the peripheral nervous system, many fibers are insulated by myelin produced by Schwann cells, which increases conduction velocity. Gaps in myelination, called nodes of Ranvier, facilitate saltatory conduction.

Nerves are categorized by the information they carry: sensory (afferent) nerves relay touch, temperature, pain, and proprioception to the CNS; motor (efferent) nerves carry signals from the CNS to muscles; and mixed nerves contain both sensory and motor fibers. Autonomic nerves regulate involuntary functions such as heart rate, digestion, and glandular activity and include sympathetic and parasympathetic components in more complex organisms.

Conduction velocity depends on fiber diameter and myelination; larger, myelinated fibers conduct faster. Nerve signals are often organized into reflex arcs, allowing rapid, automatic responses without cortical input.

Peripheral nerves are susceptible to injury from trauma, compression, or disease, leading to neuropathies or motor deficits. In the peripheral nervous system, axons can regenerate under certain conditions, guided by Schwann cells and the extracellular environment, though regeneration is slow and often incomplete compared with other tissues.