Nerve Impulse

(redirected from Nerve impulses)
Also found in: Dictionary, Thesaurus, Medical, Legal.

nerve impulse

[′nərv ‚im‚pəls]
(neuroscience)
The transient physicochemical change in the membrane of a nerve fiber which sweeps rapidly along the fiber to its termination, where it causes excitation of other nerves, muscle, or gland cells, depending on the connections and functions of the nerve.

Nerve Impulse

 

a wave of excitation that spreads along a nerve fiber; it transmits information from the peripheral receptor (sensory) endings to the nerve centers inside the central nervous system, and from there to the performing apparatus—the skeletal musculature, the smooth muscles of the internal organs and vessels, and the glands of external and internal secretion.

The main bioelectric manifestation of a nerve impulse is the action potential (AP), or peaked fluctuation of electrical potential, caused by changes in the ionic permeability of the membrane. Increase in permeability during AP leads to intensification of cation flow (Na+ and Ca2+) to and from the interior of the nerve fiber (K+). As a result, the decomposition of compounds rich in energy—adenosine triphosphate and phos-phocreatine—and the decomposition and synthesis of proteins and lipids are intensified; glycolysis and tissue respiration are activated; certain biologically active compounds (acetylcholine, norepinephrine) are freed from the bound state; and the heat production of the nerve fiber is increased.

The velocity at which a nerve impulse travels varies from 0.5 m/sec (in the thinnest fibers of the autonomic nervous system) to 100–120 m/sec (in the thickest motor and sensory nerve fibers). The propagation of a nerve impulse is ensured by local currents that arise between the excited, negatively charged parts and the resting parts of the fiber.

Under natural conditions, series of nerve impulses run continuously along the nerve fibers, both in the peripheral parts of the nervous system and in its central parts. The frequency of these rhythmic discharges depends on the strength of the stimulus that produces them. During moderate motor activity the discharge frequency is 50–100 impulses per second in the motor nerve fibers; in the majority of sensory fibers it attains 200 a second. Some nerve cells (for example, the interneurons of the spinal cord) discharge at a frequency reaching 1,000–1,500 a second.

B. I. KHODOROV

References in periodicals archive ?
And the proteins then send nerve impulses, which make the pig feel hungry.
When any part of the myelin sheath or nerve fiber is damaged or destroyed, nerve impulses traveling to and from the brain and spinal cord are distorted or interrupted, producing a wide variety of symptoms.
Myelin is critical for allowing nerve impulses to be transmitted quickly and affects our ability to walk, speak and see.
Three small bones in the middle ear help transfer sound vibrations to the inner ear where they become nerve impulses that the brain interprets as sound.
Those who were deficient were less sensitive to touch, and nerve impulses traveled over their nerves more slowly than impulses in people with higher B-12 levels.
Normally cells that respond to light, called photoreceptors, pick up signals and transfer that information as nerve impulses to ganglion cells.
It allows them to make countless such cells and try to find why motor neurones - which carry nerve impulses to the body's muscles - degenerate, leading to paralysis and ultimately death.
The message travels as nerve impulses through a threadlike axon, heading toward a synapse (space between neurons).
The eyes provide us with a precise, three-dimensional and focused view of the world by converting light energy to nerve impulses which are sent to the visual centre of the brain.
In small controlled quantities Botox interrupts nerve impulses and paralyse muscles and can be used to smooth out fine lines and wrinkles on the face.
The assumption is that nerve impulses in the optic nerve cause a nerve discharge in the trigeminal fibres, which produces the sneezing.