Editing Nervous system (section)

==Pathology==
{{Main|Neurology}}

{{See also|Psychiatry}}
[[File:CNS protection.jpg|thumb|267x267px|Layers protecting the brain and spinal cord]]
The central nervous system is protected by major physical and chemical barriers. Physically, the brain and spinal cord are surrounded by tough [[meninges|meningeal]] membranes, and enclosed in the bones of the [[skull]] and [[vertebral column]], which combine to form a strong physical shield. Chemically, the brain and spinal cord are isolated by the [[blood–brain barrier]], which prevents most types of chemicals from moving from the bloodstream into the interior of the CNS. These protections make the CNS less susceptible in many ways than the PNS; the flip side, however, is that damage to the CNS tends to have more serious consequences.

Although nerves tend to lie deep under the skin except in a few places such as the [[ulnar nerve]] near the elbow joint, they are still relatively exposed to physical damage, which can cause pain, loss of sensation, or loss of muscle control. Damage to nerves can also be caused by swelling or bruises at places where a nerve passes through a tight bony channel, as happens in [[carpal tunnel syndrome]]. If a nerve is completely transected, it will often [[nerve regeneration|regenerate]], but for long nerves this process may take months to complete. In addition to physical damage, [[peripheral neuropathy]] may be caused by many other medical problems, including genetic conditions, metabolic conditions such as [[diabetes]], inflammatory conditions such as [[Guillain–Barré syndrome]], vitamin deficiency, infectious diseases such as [[leprosy]] or [[shingles]], or poisoning by toxins such as heavy metals. Many cases have no cause that can be identified, and are referred to as [[idiopathic]]. It is also possible for nerves to lose function temporarily, resulting in numbness as stiffness—common causes include mechanical pressure, a drop in temperature, or chemical interactions with [[local anesthetic]] drugs such as [[lidocaine]].

Physical damage to the spinal cord may result in [[paralysis|loss of sensation or movement]]. If an injury to the spine produces nothing worse than swelling, the symptoms may be transient, but if nerve fibers in the spine are actually destroyed, the loss of function is usually permanent. Experimental studies have shown that spinal nerve fibers attempt to regrow in the same way as nerve fibers, but in the spinal cord, tissue destruction usually produces scar tissue that cannot be penetrated by the regrowing nerves.

Neurological practice draws heavily on the fields of neuroscience and psychiatry to treat diseases of the nervous system using various techniques of [[neurotherapy]].<ref name="International Neuromodulation Society_2024">International Neuromodulation Society, Retrieved 10 January 2025 from: https://www.neuromodulation.com/ </ref><ref name="EEE Brain 2019">IEEE Brain (2019). "Neurotherapy: Treating Disorders by Retraining the Brain". ''The Future Neural Therapeutics White Paper''. Retrieved 21.01.2025 from: https://brain.ieee.org/topics/neurotherapy-treating-disorders-by-retraining-the-brain/#:~:text=Neurotherapy%20trains%20a%20patient's%20brain,wave%20activity%20through%20positive%20reinforcement </ref><ref name="Val Danilov Origin Neurostimulation_2024">Val Danilov I (2023). "The Origin of Natural Neurostimulation: A Narrative Review of Noninvasive Brain Stimulation Techniques." ''OBM Neurobiology'' 2024; 8(4): 260; https://doi:10.21926/obm.neurobiol.2404260.</ref>