Saltatory conduction
In
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 at rates significantly higher than would be possible in unmyelinated axons (150 m/s compared to 0.5 to 10 m/s).[1] 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.[2]
Distribution
Saltatory conduction occurs widely in the myelinated nerve fibers of vertebrates, but was later discovered in a pair of medial myelinated
See also
- Bioelectrochemistry
- Cable theory
- Electrophysiology
- Ephaptic coupling – Form of nervous system communication
- GHK current equation– Expression of the ionic flux across a cell membrane
- Goldman equation – Generalization of the Nernst equation for the membrane potential
- Hindmarsh–Rose model – Of the spiking-bursting behavior of a neuron
- Hodgkin–Huxley model – Describes how neurons transmit electric signals
- Neurotransmission – Impulse transmission between neurons
- Patch clamp – Laboratory technique in electrophysiology
- Quantitative models of the action potential
- Myelination– Fatty substance that surrounds nerve cell axons to insulate them and increase transmission speed
References
- ^ Purves D, Augustine GJ, Fitzpatrick D (2001). "Increased Conduction Velocity as a Result of Myelination". Neuroscience (2nd ed.). Sunderland (MA): Sinauer Associates.
- ^ Tamarkin D. "Saltatory Conduction of APs". Archived from the original on 30 October 2014. Retrieved 6 May 2014.
- ^ Hsu K, Tan TP, Chen FS (August 1964). "On the excitation and saltatory conduction in the giant fiber of shrimp (Penaeus orientalis)". Proceedings of the 14th National Congress of the Chinese Association for Physiological Science: 7–15.
- ^ Hsu K, Tan TP, Chen FS (1975). "Saltatory conduction in the myelinated giant fiber of shrimp (Penaeus orientalis)". KexueTongbao. 20: 380–382.
- S2CID 33273673.
- S2CID 11826323.
- PMID 8271510.
Further reading
- Saladin K. "Saltatory conduction". Biology Online.
- Anatomy & physiology : the unity of form and function (6th ed.). McGraw-Hill. 2011. ISBN 978-0-07-768033-6.