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Nervous System Damage
At the most basic level, the function of the nervous system is to send signals from one part of the body to another. This is accomplished by transmitting from one cell to another. There are multiple ways that a cell can send signals to other cells. One is by releasing chemicals called hormones into the internal circulation, so that they can "broadcast" or be carried to distant parts of the body. In contrast to the "broadcast" mode of signaling, the nervous system provides "point-to-point" signals in which neurons project their axons to specific target areas and make synaptic connections with specific target cells. The "point-to-point" neural signaling is capable of a much higher level of specificity than hormonal signaling. It can also travel much faster, with the fastest nerve signals traveling at speeds that exceed 100 meters per second.

At a more integrative level, the primary function of the nervous system is to control the body. This is done by extracting information from the environment using sensory receptors, sending signals that encode this information into the central nervous system (CNS), processing the information to determine an appropriate response, and sending output signals to muscles or glands to activate the response. The evolution of a complex nervous system has made it possible for various animal species to have advanced perception abilities such as vision, complex social interactions, rapid coordination of organ systems, and integrated processing of concurrent signals. In humans, the sophistication of the nervous system makes it possible to have language, abstract representation of concepts, transmission of culture, and many other features of human society that would not exist without the human brain.

Pathology of Nerve Damage

The nervous system is susceptible to damage in a many number of ways, as a result of genetic defects, physical damage from trauma or poison, infection, or simply aging. The medical specialty of neurology studies the causes of nervous system malfunction, and looks for interventions that can alleviate it.

Neuropathology is the study of disease of nervous system tissue, usually in the form of either surgical biopsies or sometimes whole brains in the case of autopsy. Neuropathology is a subspecialty of anatomic pathology, neurology, and neurosurgery.

If a disease of the nervous system is suspected, and the diagnosis cannot be made by less invasive methods, a biopsy of nervous tissue is taken from the brain or spinal cord to aid in diagnosis. Biopsy is usually requested after a mass is detected by medical imaging.

The nervous system is susceptible to malfunction in a wide variety of ways, as a result of genetic defects, physical damage due to trauma or poison, infection, or simply aging. The medical specialty of neurology studies the causes of nervous system malfunction, and looks for interventions that can alleviate it.

The central nervous system (CNS) is protected by major physical and chemical barriers. Physically, the brain and spinal cord are surrounded by tough meningeal membranes, and enclosed in the bones of the skull and spinal vertebra, 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 peripheral nervous system (PNS) even though that damage to the CNS tends to have more serious consequences.

Although peripheral nerves tend to lie deep under the skin and muscle, except in a few places such as 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 peripheral nerve is completely transected (cut), it will often 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's also possible for peripheral nerves to lose function temporarily, resulting in numbness as stiffness. The 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 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 peripheral nerve fibers, but in the spinal cord, tissue destruction usually produces scar tissue that can't be penetrated by the regrowing nerves.

There are three types of nerves, or neurons, in the body:

Autonomic nerves - These nerves control the involuntary or partially voluntary activities of your body, including heart rate, blood pressure, digestion, and temperature regulation.
Motor nerves - These nerves control your movements and actions by passing information from your brain and spinal cord to your muscles.
Sensory nerves - These nerves relay information from your skin and muscles back to your spinal cord and brain. The information is then processed to let you feel pain and other sensations.

Nerve pain and nerve damage can be mild. But, because nerves are essential to all you do, nerve pain and damage can seriously affect your quality of life.