The Nervous System in Relation to Neuropathy

We know that neuropathy is a disease of the nervous system and have a rough idea that it's to do with the disruption, or breakdown of signal paths, thus creating all the symptoms that we're well aware of - short circuits in the system, that sort of thing. However, what do we really understand when we are told we have a neurological disease? What do the nerves actually do and why do they stop working as they should wwhen we get neuropathy?

This article from Medifocus Health (see link below)gives an excellent explanation of exactly how the various nerves in our bodies work and what goes wrong when we suffer from neuropathy. Very much worth a read.

The Nervous System

The nervous system controls the smooth functioning of all systems in the body as well as all interactions between the human being and the environment. It consists of two networks:





•Central nervous system - includes the brain and spinal cord

•Peripheral nervous system - includes the nerves that lead from the brain and spinal cord to all parts of the body. This is the system affected by peripheral neuropathy. There are two components to the peripheral nervous system:

◦somatic nervous system - regulates body movement through control of skeletal muscles and connects the brain to the outside environment through the five senses. It is the "voluntary" nervous system that enables people to react to environmental stimuli.

◦autonomic nervous system- controls automatic, involuntary functions including heart rate, blood pressure, breathing, digestion, and bladder function. This system is responsible for maintaining homeostasis, the state of equilibrium where all body systems are working and interacting correctly.

An extensive system made up of three types of specialized nerves makes up the peripheral nervous system:

*Motor nerves - carry messages from the brain to organs, muscles, and glands, and are responsible for the ability to move any part of the body. These are called efferent nerves. * Sensory nerves - carry information from organs (e.g., the skin) to the central nervous system where it is processed into sensation (e.g., touch, temperature changes, and vibrations). These are called afferent nerves. * Autonomic nerves - control involuntary functions such as heart rate, digestion, respiration rate, and perspiration.

Each peripheral nerve cell (neuron) in the human body has three parts:

•Cell body (also called soma), which is similar to the cell body of all other cells.

•Dendrites - fibers of varying sizes which extend from the cell body and are the sensory terminals of the neuron. They receive messages from neighboring cells and transmit them to the cell body.

•Axon (also called a nerve fiber) - a long slender projection that extends from the cell body and transfers a signal from the cell body to another nerve or muscle cell. Axons can be either myelinated (insulated by the myelin sheath made up of specialized cells) or unmyelinated. The presence or absence of myelin affects the speed of transmission of impulses; conduction speed is significantly faster in myelinated cells.

Nerve fibers may be either large or small.

Large Nerve Fibers

Large fibers are long nerve fibers that are myelinated and enable very fast conduction of impulses to the brain and spinal cord. They carry non-nociceptive information and are not normally associated with pain. Lesions or injury to large fibers can affect many functions including:

•Motor function
•Vibration perception
•Positional sense
•Perception of temperature

Symptoms associated with large fiber neuropathy include:
•Numbness
•Tingling
•Weakness
•Loss of deep reflexes

Small Nerve Fibers

Small nerve fibers may or may not be myelinated and each type involves different sensations. Regardless of whether or not they are myelinated, they contain nociceptors which are highly sensitive to pain and paresthesia (abnormal sensations such as tingling, pricking, or burning).

Symptoms of small fiber neuropathy are many and include:

•Pain described as burning, stabbing, prickling, jabbing, or lancinating (piercing)
•Sensation of "broken glass", "burning sand", or "ice pick in the bone"
•Tight band-like pressure
•Insensitivity to heat and cold
•Autonomic dysfunction (malfunctioning of the autonomic nervous system)

While small fiber neuropathy may be caused by conditions such as diabetes or HIV, the cause of most cases of small fiber peripheral neuropathy is unknown and is called idiopathic peripheral neuropathy. It is estimated that an underlying cause for small fiber neuropathy is found in less than 10% of patients. Small fiber neuropathy is the most common type of PN in people over the age of 50 and is often unrecognized by physicians. It is very painful to the point of being debilitating and responds slowly to medication, if at all.

In peripheral neuropathy involving both large and small fibers, small fiber damage usually precedes large fiber dysfunction and occurs typically in the lower limbs.

http://www.medifocushealth.com/NR021/Introduction-to-Peripheral-Neuropathy_The-Nervous-System.php