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

References in periodicals archive ?
(14) have compared the EABR and EAP (Electrically Evoked Whole-Nerve Action Potential) measurements in 10 postlingual adults with Nucleus CI 24R and Nucleus CI 24M implants, and reported to have found significant difference between the EAP and the EABR thresholds in the Nucleus CI 24M users, but no significant difference in Nucleus CI 24R users.
(50),(51) This local NMDA-R-dependent potential, a highly supralinear summation of multiple inputs, has a much more significant impact on the generation of an action potential than the summation of the separate effects, and enhances the generation of action potentials at the soma.
For acoustically evoked brainstem responses, the peripheral action potentials of the auditory nerve can be identified in the recording (wave I), but for electrically evoked responses recorded with an ABR recording setup, these potentials are embedded in the stimulus artifact [4].
elegans cells also produce action potentials; yet they note that this is not the norm for this animal's neurons.
[12] Both latency and conduction velocity depend on the intact, and myelinated nerve fiber as the myelin and node is essential for the fast action potential propagation.
Following the ideas of evolution equations (see for example [15,16], it is possible to derive also an evolution equation for the action potential [36]:
L-type and T-type [Ca.sup.2+] currents are important in the generation of phase 4, and L-type [Ca.sup.2+] current is also important in the generation of phase 0 of SAN and atrioventricular node action potentials. The T-type [Ca.sup.2+] channels also have roles in cell growth and cardiovascular remodeling.
Bean, "Roles of tetrodotoxin (TTX)-sensitive Na+ current, TTX-resistant [Na.sup.+] current, and [Ca.sup.2+] current in the action potentials of nociceptive sensory neurons," The Journal of Neuroscience, vol.
Some interesting discoveries have been found during the study of the energy distribution properties of structural neural networks [24]: (1) the theory of neural energy coding is based on the use of a global concept of energy; (2) neurons release their stored energy within a very short time (negative energy) at the beginning of firing action potential, after which the oxyhemoglobin provides them with biological energy, and this mechanism contradicts the traditional theory of pure energy consumption in neurons; (3) the distribution of the negative energy, as assessed by parameter studies, reflects the neural network parameters and neural oscillation with a high consistency.
found that treatment of differentiating hESCs with Noggin and a RA inhibitor increased the expression of ventricular-specific genes (IRX4 and MLC2v), and 83% of the obtained cardiomyocytes had ventricular-like action potentials [51].
Caption: Figure 6: Comparison of normal and abnormal epicardium action potentials. (a) shows the normal epicardium action potential, (b) shows the action potential of epicardium with myocardial ischemia, and (c) shows the action potential of epicardium with heart failure.
One can therefore measure and record the action potential of individual cells using a special camera.

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