Action Potentials


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Action Potentials

 

changes of bioelectric potentials in an electroencephalogram or in a recording of electrical activity of other brain structures in response to stimuli arriving via the ascending or sensory tracts. A distinction is made between primary and secondary potentials or reactions. Primary action potentials or primary reactions (PR) with a short latent period arise ten to 20 milliseconds after the arrival of impulses. The PR is recorded in a limited area of the cortical projection of the receptor stimulated (for example, after the eye is stimulated by a flash of light, the PR arises in the occipital cortex in the form of monophasic or biphasic oscillations of biopotential). Secondary action potentials or secondary reactions (SR) have longer latent periods (from 30 to 200 milliseconds) and a wider region of propagation. SR arise first in the same area of the brain as the PR, but their shape is more complex, and they are polyphasic. Still more complex SR arise at the same time or later in other cerebrocortical centers (localized reactions) or even throughout the cortex (generalized reactions).

The PR is the algebraic sum of the initial changes in biopotentials of cortical neurons reacting to the first volley of im-pulses reaching the cortex from the receptor through the specific direct sensory tracts (lemniscus). The causes of local SR include reactions occurring in the corresponding cortical neurons and propagation of excitation (irradiation) along the associative neural pathways to the nearest or more distant neurons. Generalized SR are believed to arise following stimulation of the cerebral cortex through nonspecific neural pathways (from the reticular formation and limbic system).

Maps showing the cortical projection of the visual, acoustic, cutaneous, and other receptors have been constructed on the basis of recordings of PR. The origin of PR and SR is closely related to the processing of information received by the organism and formation of conditioned reflexes in the nervous system. Recordings of action potentials are used clinically to determine the precise location of a pathological process in the brain.

REFERENCES

Roitbak, A. I. “Vyzvannye potentsialy kory bol’shikh polusharii.” In the collection Sovremennye problemy elektrofiziologicheskikh issledovanii nervnoi sistemy. Moscow, 1964.
Kullanda, K. M. “Vtorichnyye bioelektricheskie reaktsii kory bol’shikh polusharii.” In the collection: Sovremennye problemy elektrofiziologicheskikh issledovanii nervnoi sistemy. Moscow, 1964.
Puchinskaia, L. M. Elektrokortikal’nye reaktsii na svet u cheloveka. Novosibirsk, 1967.

E. A. ZHIRMUNSKAIA

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The HH model is a benchmark for action potential models, but further studies have improved it considerably by explaining the ion pumps in more details [32-34].
Subtype-specific promoter-driven action potential imaging for precise disease modelling and drug testing in hiPSC-derived cardiomyocytes," European Heart Journal, 2016; ehw189 DOI: 10.
Both the SFN- and CN-jitters reflect a similar physiological phenomenon (variability in the arrival time of muscle fiber action potentials to the recording electrode) and clinical significance.
The recommended criteria for an abnormal study is: 1) a value for the mean MCD of 20 fiber pairs greater than the 95% upper confidence limit for that muscle; or 2) jitter values in more than 10% of pairs greater than the 95% upper CL for action potential pairs in a muscle (7).
Also, we calculate the time profile for action potentials in the RCLSJHH model under different conditions to understand C and K to understand generalized synchronization.
In motor conduction studies, motor distal latency (MDL) and compound muscle action potential (CMAP) values were recorded for the median and ulnar nerves by stimulating at the level of the wrist and antecubital region in the abductor pollicis brevis (APB) and abductor digiti minimi (ADM) muscles in the upper extremity.
Bioelectrical therapies use electrical discharges to override action potentials generated within the body, thus altering nerve function in the stimulated area.
2] for the membrane capacitance, the discharging current density for generation of action potential can be estimated as follows:
Cochlear neurons transmit information about the intensity (loudness) of the sound to central auditory regions in part by the number of action potentials that are generated.
Sheng, "Effects of berberine on ventricular fibrillation threshold and action potentials in rabbit myocardium in vivo," Clinical and Experimental Pharmacology, vol.
As a result of increased duration of the action potential and refractory period, patients with hypokalemia are at increased risk for certain dysrhythmias like ventricular tachycardia.
Electrocochleographic recordings were made from an implanted round window electrode and the compound action potentials were measured daily at 2-16 kHz for 7 days.

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