Nerve fiber

definition

A nerve fiber is a portion of a nerve. A nerve is made up of several bundles of nerve fibers. These nerve fiber bundles contain many nerve fibers.
Each nerve fiber is surrounded by the so-called endoneurium, a kind of protective sheath around each nerve fiber. The endoneurium consists of connective tissue and elastic fibers and because the blood vessels run in it, it also has an important function in nourishing the Schwann cells and thus the nerve fibers. To join together to form a bundle of nerve fibers, there is the so-called Perineurium. It surrounds many nerve fibers and thus holds a bundle of nerve fibers together. Many nerve fiber bundles are held together by the so-called Epineurium surround and in their entirety form a nerve.

A general distinction is made medullary nerve fibers of non-medullary nerve fibers. A commonly used synonym for the nerve fiber is that Axon or that Neurite, Strictly speaking only that Axon together with the surrounding cell membrane (the axolemm) represents a nerve fiber.

The nerve fiber is used to transmit Information from the cell body (Soma) from to the End button (Telodendrons), which then with a new cell body (Soma) get in contact to pass the information on.

The nerve fiber begins from the so-called Axon moundswho added to that Cell body of a nerve cell is added. From there, the nerve fiber extends to its branching into the terminal button.

Medullary nerve fibers

Medullary (myelinated) Nerve fibers are characterized by the fact that the Axon is surrounded by a Myelin sheath. A nerve fiber can be thought of as similar like some kind of cable and the myelin sheath is one Insulating layer around the cable around. Myelination is in central nervous system (short CNS) and in peripheral nervous system (short PNS) differently.
in the CNS will the Myelin sheath formed by so-called oligodendrocytes. In the PNS, however, Schwann cells form the insulating layer.
These Myelin sheath but it is not consistently instead it always has short interruptions in which the nerve fiber is "naked", this interruption being referred to as RANVIER'S lace ring designated. This serves one faster conduction of excitation. This rapid form of conduction of excitation is known as Saltatory conduction of excitation. Here the excitation "jumps" from ring to ring and does not have to complete length of nerve fiber irritate.
In every lace-up ring it will be Action potential formed and passed on from lace ring to lace ring. This is much faster than that continuous spread of excitationas is the case with non-medullary nerve fibers.

Adenoved nerve fibers

Adenoved nerve fibers can be found above all where information does not have to be passed on so quickly. For example are Pain nerve fiberswho have favourited information on the perception of pain brain forward partly unmarked.
This is important because there is pain, for example have to last a long time. in the CNS are medullary nerve fibers not wrapped at allIn the PNS, however, the nerve fibers are partially covered with Schwann cells.

function

A nerve fiber has the function informationthat on Axon mounds enter the nerve cell, forward to the end buttonwhich then represent a synaptic connection with another Nerve cell or directly with one Muscle- or Gland cell.

A Nerve fiber can get the information from the brain out into the Periphery of the body lead, for example to the skin. In this case it is called efferent nerve fiber designated. A afferent nerve fiber on the other hand, the information passes from the skin or organs to the brain or the spinal cord, for example.
To illustrate this, one has to imagine that when one looks at the Ballpoint pen touches and felt with your fingers, this over the afferent nerve fibers happens. This tactile information from the skin is passed on to the brain.
But if we do write something with the ballpoint pen want, our brain must first have the Control movement. This movement plan is then sent to the efferent nerve fibers passed on, which then pass the information on to our hand muscles. Now we can grab the pen and start writing. All of this happens within a few milliseconds.

To the To maximize the speed of information forwarding there are special thick nerve fibers. These forward information particularly quickly. The so-called lead the fastest Aalpha fiber with a Line speed of up to 120m / sec. They lead the slowest thin and medullary carbon fibers at a speed of less than 2m / sec. They provide information about dull pain.
In addition to the Thickness of nerve fiber is also that length a decisive criterion. There are annoy, the only a few millimeters long and therefore only have to transport the information over a very short distance. Other nerve fibers, however, can up to a meter long be and therefore also have one very long distance over which the action potential and thus the information must be passed on.

Nerve fiber quality

Of the Nerve fiber quality one speaks to describe from what place of the body forwarded from information.
For one thing, there is somatosensitive nerve fibersthat too somatoafferent to be named. Somato refers to the body, sensitive or afferent, refers to the fact that the information from the body to the brain or that Spinal cord (together that CNS) to get redirected.
A somatosensitive nerve fiber could be a nerve fiber that supports the Forwards information about our sense of touch. The opposite is that somatosensory or somato-efferent nerve fiber. This leads from brain from the information about how our body should behave. For example, with the help of somatomotor nerve fibers, our Muscles moved at will.
Then there are those viscerosensitive nerve fiber qualities. These lead to our brain the information, how our organs are doing. This nerve fiber quality is very involuntarily can, however, for example with a Heart attack, be of great importance to the patient.
Then there are those visceromotor nerve fiber. This can be the Directly affect organs from the brain and is completely unconscious to the patient himself. This is also very important because otherwise we would have to keep thinking about breathing, ours To make your heart beat and after eating the Moving bowels so that it can digest adequately.