III. disease:

Central nervous system is protected by physical barriers and large chemical. Physically, the brain and spinal cord are surrounded by tough brain membranes, and enclosed in the bones of the skull and spinal vertebrae, which combine to form a strong physical shield. Chemistry, brain and spinal cord are isolated by the so-called blood-brain barrier, which prevents most types of chemicals from moving from the blood into the central nervous system. These safeguards make the CNS less susceptible in many ways than the PNS, the left side, however, is the damage to the central nervous system tend to have more serious consequences.

Although nerves tend to lie deep under the skin, except in a few places such as the nerves near the elbow joint office, they are still relatively exposed to physical damage, can cause pain, loss of sensation, or loss of muscle control. Nerve damage can also be caused by swelling or bruises where the nerve passes through a tight channel bone, as occurs in carpal tunnel syndrome. for long nerves this process may take several months to complete. In addition to physical damage, peripheral neuropathy can 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 toxins such as heavy metals. In many cases, no cause can be identified, and are referred to as idiopathic. It is also possible for nerves to lose function temporarily, resulting in numbness as hard-common causes include mechanical pressure, reduced temperature, or chemical interactions with local anesthetic types drugs such as lidocaine.

Physical damage to the spinal cord can result in loss of sensation or movement. If spinal cord injury produced nothing worse than swelling, the symptoms may be transient, but if nerve fibers in the spine are actually destroyed, 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 the spinal cord, tissue destruction usually produces scar tissue that can not be broken by the wire regrowing nerves.