English is full of idioms related to nerves. "You've got a lot of nerve!" "He gets on my nerves." "You just have a case of nerves." These sayings come from alternate meanings for the word. According to the Online Etymology Dictionary, "nerve" has the following definitions:
- boldness (1601)
- courage (1809)
- nervousness (1839)
- impudence (1887)
Nerve activity can be affected by toxins, trauma and disease.
- Toxic substances interfere with sodium or potassium channels, whose actions underlie the action potential. Such toxic substances include venoms, heavy metals (like mercury and lead) and anesthetics.
- Trauma happens when limbs or vertebrae become fractured and the nerves close to them are crushed, pinched or even severed. This can result in pain, numbness, complete loss of feeling or loss of movement. The extent of damage and recovery depends upon the severity and location of the injury.
- A pinched nerve is a common problem in which a bone, joint or muscle compresses a nerve and impairs its conduction, leading to pain and numbness. This often occurs between vertebrae in the spine, where swelling discs can compress the nerves as they exit.
- Another common example is carpal tunnel syndrome, where repeated motions of the wrist (like from typing on computers) causes swelling in the bone tunnel (carpal bones) where the radial and ulnar nerves pass through the wrist into the fingers. Sciatica is a similar nerve problem where an injured spinal disc compresses the sciatic nerve to the leg, causing pain and numbness.
- Some diseases directly affect nerve function. For example, multiple sclerosis (MS) occurs when the myelin surrounding nerves degrades, which affects nerve conduction. MS may be caused by an autoimmune response, where the patient's own immune system attacks the myelinated nerves. Myasthenia gravis (MG) is a disease in which the synaptic transmission between nerve cells and muscle cells is disrupted.
Your nerves must conduct impulses correctly for you to regulate your internal environment, respond to your external environment, think, and learn. When nerves become impaired, many body functions or quality of life can be affected.
To learn more about nerves, check out the links on the following page.