![Propagation of action potential along myelinated nerve fiber en](https://upload.wikimedia.org/wikipedia/commons/6/68/Propagation_of_action_potential_along_myelinated_nerve_fiber_en.svg)
In
neuroscience
Neuroscience is the scientific study of the nervous system (the brain, spinal cord, and peripheral nervous system), its functions and disorders. It is a multidisciplinary science that combines physiology, anatomy, molecular biology, development ...
, saltatory conduction () is the propagation of
action potential
An action potential occurs when the membrane potential of a specific cell location rapidly rises and falls. This depolarization then causes adjacent locations to similarly depolarize. Action potentials occur in several types of animal cells, ...
s along
myelin
Myelin is a lipid-rich material that surrounds nerve cell axons (the nervous system's "wires") to insulate them and increase the rate at which electrical impulses (called action potentials) are passed along the axon. The myelinated axon can be ...
ated
axon
An axon (from Greek ἄξων ''áxōn'', axis), or nerve fiber (or nerve fibre: see spelling differences), is a long, slender projection of a nerve cell, or neuron, in vertebrates, that typically conducts electrical impulses known as action po ...
s from one
node of Ranvier
In neuroscience and anatomy, nodes of Ranvier ( ), also known as myelin-sheath gaps, occur along a myelinated axon where the axolemma is exposed to the extracellular space. Nodes of Ranvier are uninsulated and highly enriched in ion channels, al ...
to the next node, increasing the
conduction velocity
In neuroscience, nerve conduction velocity (CV) is an important aspect of nerve conduction studies. It is the speed at which an electrochemical impulse propagates down a neural pathway. Conduction velocities are affected by a wide array of factor ...
of action potentials. The uninsulated nodes of Ranvier are the only places along the axon where ions are exchanged across the axon membrane, regenerating the action potential between regions of the axon that are insulated by myelin, unlike
electrical conduction
Electrical resistivity (also called specific electrical resistance or volume resistivity) is a fundamental property of a material that measures how strongly it resists electric current. A low resistivity indicates a material that readily allows ...
in a simple circuit.
Mechanism
Myelinated axons only allow action potentials to occur at the unmyelinated nodes of Ranvier that occur between the myelinated internodes. It is by this restriction that saltatory conduction propagates an action potential along the axon of a
neuron
A neuron, neurone, or nerve cell is an electrically excitable cell that communicates with other cells via specialized connections called synapses. The neuron is the main component of nervous tissue in all animals except sponges and placozoa. N ...
at rates significantly higher than would be possible in unmyelinated axons (150 m/s compared to 0.5 to 10 m/s). As sodium rushes into the node it creates an electrical force which pushes on the ions already inside the axon. This rapid conduction of electrical signal reaches the next node and creates another action potential, thus refreshing the signal. In this manner, saltatory conduction allows electrical nerve signals to be propagated long distances at high rates without any degradation of the signal. Although the action potential appears to jump along the axon, this phenomenon is actually just the rapid conduction of the signal inside the myelinated portion of the axon.
If the entire surface of an axon were insulated, action potentials could not be regenerated along the axon resulting in signal degradation.
Energy efficiency
In addition to increasing the speed of the nerve impulse, the myelin sheath helps in reducing energy expenditure over the axon membrane as a whole, because the amount of sodium and potassium ions that need to be
pumped to bring the concentrations back to the resting state following each action potential is decreased.
Distribution
Saltatory conduction occurs widely in the myelinated nerve fibers of vertebrates, but was later discovered in a pair of medial myelinated
giant fibers of ''
Fenneropenaeus chinensis
The Chinese white shrimp, oriental shrimp, or fleshy prawn (''Fenneropenaeus chinensis'') is a species of shrimp. It is cultivated at an industrial level off mainland China. Production was devastated by a series of epidemics in the 1990s and ear ...
'' and ''
Marsupenaeus japonicus
''Marsupenaeus'' is a monotypic genus of prawn. It contains a single species, ''Marsupenaeus japonicus'', known as the kuruma shrimp, kuruma prawn, or Japanese tiger prawn. It occurs naturally in bays and seas of the Indo-West Pacific, but has a ...
''
shrimp
Shrimp are crustaceans (a form of shellfish) with elongated bodies and a primarily swimming mode of locomotion – most commonly Caridea and Dendrobranchiata of the decapod order, although some crustaceans outside of this order are refer ...
, as well as in a median giant fiber of an
earthworm
An earthworm is a terrestrial invertebrate that belongs to the phylum Annelida. They exhibit a tube-within-a-tube body plan; they are externally segmented with corresponding internal segmentation; and they usually have setae on all segments. Th ...
. Saltatory conduction has also been found in the small- and medium-sized myelinated fibers of ''
Penaeus
''Penaeus'' is a genus of prawns, including the giant tiger prawn (''P. monodon''), the most important species of farmed crustacean worldwide. The genus has been reorganised following a proposition of Pérez Farfante and Kensley based on morph ...
'' shrimp.
See also
*
Bioelectrochemistry
Bioelectrochemistry is a branch of electrochemistry and biophysical chemistry concerned with electrophysiological topics like cell electron-proton transport, cell membrane potentials and electrode reactions of redox enzymes.
History
The beginni ...
*
Cable theory
Classical cable theory uses mathematical models to calculate the electric current (and accompanying voltage) along passive neurites, particularly the dendrites that receive synaptic inputs at different sites and times. Estimates are made by model ...
*
Electrophysiology
Electrophysiology (from Greek , ''ēlektron'', "amber" etymology of "electron"">Electron#Etymology">etymology of "electron" , ''physis'', "nature, origin"; and , '' -logia'') is the branch of physiology that studies the electrical properties of b ...
*
*
*
*
*
*
*
*
*
References
Further reading
*
*
External links
Saltatory conduction - Scholarpediacell biology - Why is saltatory conduction in myelinated axons faster than continuous conduction in unmyelinated axons?
{{DEFAULTSORT:Saltatory Conduction
Neurophysiology
de:Erregungsleitung#Saltatorische Erregungsleitung