A nerve is a closed, rope-like bundle of Nerve fibers with a covering made of connective tissue in the peripheral nervous system. Together with other nerves, this forms the path for electrochemical impulses that are transmitted along the nerve fibers to the peripheral organs.
What are nerves?
Schematic representation of the anatomy and structure of a nerve cell. Click to enlarge.The totality of all nerve cells (neurons) and glial cells (isolation and connection of neurons) is called the nervous system. The brain and spinal cord form the central nervous system (CNS), all nerves outside the CNS belong to the peripheral nervous system (PNS).
The simplest annoy are unipolar nerves - simple sensory cells such as those in the eyes, while biopolar nerve cells transmit sensory impulses. The most common nerve cells are so-called multipolar cells, which mainly occur in the spinal cord. Afferent nerves carry signals from sensory neurons, such as the mechanoreceptors in the skin, to the central nervous system.
Efferent nerves, in turn, carry signals from the central nervous system to the muscles and glands. The PNS includes both the spinal nerves (connection to the spinal cord through the spine), the cranial nerves (connection to the brain stem) and the nerves of the visceral nervous system (enteric nervous system).
Anatomy & structure
Neurons have special structures to send signals to other cells quickly and precisely. Each Nerve cell forms a string-like structure, which consists of a cell body with appendages, so-called axons (nerve fibers).
Within a nerve, each axon is surrounded by a layer of connective tissue (endoneurium). This endoneurium consists of an inner shell made of glycocalix and an outer sensitive network of collagen fibers. Within the endoneurium, the individual nerve fibers are surrounded by a protein liquid, similar to the cerebrospinal fluid in the central nervous system.
The nerve fibers are bundled in groups (fascicles) and again covered by connective tissue (perineurium). The connective tissue that envelops the entire nerve is called the epineurium. Nerve growth usually ends at puberty but can be re-stimulated using a molecular mechanism.
Functions & tasks
Primary function of the annoy and the nervous system is to sensorimotor control the body. It does this by extracting information from the environment using sensory receptors, sending signals encoding that information into the central nervous system, processing the information for an appropriate response, and sending output signals to muscles or glands to trigger the response in question to activate.
Even in the nervous system of a single species like humans, there are hundreds of different types of neurons, with a wide variety of morphologies and functions. The exchange between them takes place in the form of electrochemical nerve impulses at speeds of up to 120 m / s.
They migrate from one neuron to the next; when a synapse crosses, the message in question is converted from an electrical impulse to a chemical message (neurotransmitter) and then converted back into an electrical impulse.
The connections between the neurons form neural circuits that generate a perception and determine the behavior of the organism.
Diseases
The nervous system, like the rest of the organism, is prone to failure, whether as a result of genetic defects, physical damage due to trauma or poison, infections or simple aging processes. The medical department of neurology deals with the causes of malfunctions of the nervous system and their treatment or prevention.
In the peripheral nervous system, the most common type of problem is nerve conduction loss, which can have a variety of causes. These include diabetic neuropathy and demyelinating diseases such as multiple sclerosis and amyotrophic lateral sclerosis. A pinched nerve occurs when pressure is placed on a nerve, for example due to swelling from an injury or pregnancy.
Nerve damage or pinched nerves are usually accompanied by pain, numbness, weakness or paralysis, some of which can be perceived far from the actual location of the damage. If a nerve is damaged, radiating pain occurs in all areas from which the nerve cell receives input. Nerve disorders are usually diagnosed by a physical examination, including testing reflexes, running and other directed movements, muscle reactions and sensory functions, supplemented by an EMG.
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