Nerve

---- In Anatomy, a nerve is a Organe peripheral Nervous system composed of nervous fibers (or neurons, having Axone S and dendrites) able to transmit related sensitive information (body towards the Cerveau) and efferent (of the brain towards the Muscle S for the driving axons or worms of other bodies, like the Glande S). The axons composing the nerve are surrounded by their sheath of Myéline, whose synthesis is ensured by the Oligodendrocyte S.

Signal that the nerves transmit (the Potentiel action) is of nature electric, it is generated by movements of Ion S entering and outgoing of axon via channels specific, which involves a membrane Dépolarisation which is transmitted gradually, by jumps from one node to another. The nodes are zones deprived of myéline where the movements of ions take place, which allows a fast transmission of the electrical signals. These signals are born with the level from the cellular body from the Neuron and finish with the Synapse, where they are transmitted to the following neuron by a biochemical phenomenon .

Anatomy and functions

Sensory nerve and motor nerve

One distinguishes two categories of nerves according to the type of information which they convoient:
  • the sensory nerves (or sees related) make go up information since the somatic sensory receivers (located in the Peau, the Muscle S, etc) and visceral;
  • the motor nerves (or sees efferent) transport the driving order since the central nervous system towards the effector (mainly muscles, but also the Glande S) of the somatic systems or autonomous.

The nerves containers of the related and efferent ways are known as mixed.

General anatomy

The driving nervous efferent fibers are born with the level from the driving cerebral centers, called driving Cortex (or driving surfaces ) where the Motoneurone S. They are located walk on then in the Corona radiata and the Capsule interns (which are elements of the white Substance of the Cerveau), then in the cerebral trunk, and finally in the Spinal-cord, to the former horn where it passes the relai to a new group of motoneurone. This new group lets its axons form the driving former rachidian root. There exist two driving beams: the pyramidal Beam direct and cross. From there, the nervous fibers gather in nerves according to their function, emergent of marrow, and join their muscle of destination on which they will act via the driving Plaque and the Voie extrapyramidale in charge of the semi-automatic movements.

The related sensitive fibers have a dendritic termination in the target body (for example the Peau), but the cellular body of the sensitive neuron is in the rachidian Ganglion, bulge of the posterior rachidian root. The axon of this sensitive neuron walks on then in the spinal-cord, within a sensitive beam (posterior Faisceau cordonnal or Faisceau spinothalamic).

The majority of the nerves are mixed nerves, i.e. they are made up at the same time of sensitive fibers and driving fibers.

Detailed anatomy

The peripheral nerve

The nerve, if it is peripheral (i.e. if he belongs to the peripheral Nervous system), is composed of a very particular assembly of cellular prolongation (here, Axone). Several nervous fibers join in booklets by the means of a conjunctive Tissu named endonèvre (conjunctive fabric releases container of many microfibrils of Collagène). Several booklets join around an other fabric, the périnèvre (constituted of ten flattened cells covered by a basal Lame), thus forming a " group fascicules". Lastly, several " groups of fascicules" join by the means of the épinèvre (dense conjunctive fabric containing Adipocyte S and blood-vessels), giving the nerve as an anatomical unit.

Nervous fibers of the autonomous nervous system and nervous fibers which utilize the conscience

The autonomous Nervous system is the part of the nervous system responsible for the automatic functions such as digestion, sudation… these fibers have a role in the maintenance of the balance of the interior medium, or homeostasis, implies complex interactions between physiological and behavioral aspects. There can be related and efferent nerves.

One opposes the neurons to it controlling voluntarily or consciously functions such as the movement of a member.

List nerves at the man

Rachis and cranium

Upper limb

Lower extremity

External bonds

  • See a detailed diagram nerves originant of the spinal column

Simple: Nerve

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