Nerve excitation

I. Tasaki and P. M. Byrne. Optical changes during nerve excitation interpretation on the basis of rapid structural changes in the superficial gel layer of nerve fiber. Physiological Chemistry and Physics and Medical NMR, 26 101-110, 1994. 

Cyclodiene insecticides produce intense nerve excitation in both vertebrate and invertebrate species (Matsumura 1985 Matsumura and Tanaka 1984). It has been suggested that the biochemical mechanisms by which these chemicals induce hyperexcitation in the central nervous system are due to the release of neurotransmitters caused by the interactions of the insecticide with the picrotoxinin receptor. 

The mechanism of antidepressive action of this series of drugs is likely associated with their inhibition of the oxidizing deamination process of the neurotransmitters norepinephrine, epinephrine, dopamine, and serotonin, which participate in the transmission of nerve excitement in the CNS. A major drawback of these drugs is the high toxicity associated with their inhibition of not only MAO, but also a number of other nonspecific enzymes. 

Electro-osmotic oscillation (first observed by Teorell [1]—[4] in a laboratory set-up devised to mimic nerve excitation) may likely represent a common source of oscillations in various natural or synthetic electrokinetic systems such as solid microporous filters, synthetic ion-exchange membranes or their biological counterparts. The original experimental set-up, which contained all essential elements to look for when the electro-osmotic oscillations are suspected in a natural system, is schematically as follows. 

Recall from our discussion of cocaine and amphetamines that the body responds to the long-term abuse of these stimulants by creating more depressant receptor sites. Likewise, the body recognizes the excessive inhibitory actions produced by alcohol and tries to recover by increasing the number of synaptic receptor sites that lead to nerve excitation. A tolerance for alcohol therefore develops. To receive the same inhibitory effect, the drinker is forced to drink more, which induces the body to create even more excitable synaptic receptor sites. Eventually, an excess of these excitatory receptor sites leads to perpetual body tremors, which can be subdued either by more drinking or, with greater difficulty, by a long-term cessation of alcohol consumption. 

What is known about the channels through which Na+ and K+ flow during nerve excitation That the channels for the two ions are separate was shown by the fact that tetrodotoxin (found in the puffer fish)429 4293 and saxitoxin of dinoflagellates, as well as... 

The present sensor could easily discriminate between some kinds of commercial drinks such as coffee, beer and aqueous ionic drinks (Figure 11) [22], Since the standard deviations were 2 mV at maximum in this experimental condition, these three output patterns are definitely different. If the data are accumulated in the computer, any food can be easily discriminated. Furthermore, the taste quality can also be described quantitatively by the method mentioned below. In biological systems, patterns of frequency of nerve excitation may be fed into the brain, and then foods are distinguished and their tastes are recognized [4-8]. Thus, the quality control of foods becomes possible using the taste sensor, which has a mechanism of information processing similar to biological systems. 

Acetylcholine plays a recognized role in the nerve excitation scenario that we have described above very briefly. It is found in cholinergic synapses that provide stimulatory transmissions in the nervous system. Its complete neurocycle implies a coupled two-enzymes/two-compartments model with two strongly coupled events as follows ... 

Of the two different types of ionic channels, the opening of sodium channels is considered as the first step of nerve excitation. The opening of potassium channels is a delayed response and lags behind that of sodium channels. There are... 

These considerations lead us to a conclusion that nerve excitation is a very slow process and the membrane does not contain elements which has a frequency response of MHz or GHz. The only molecular species which may have such a frequency response are water molecules. However, the role of water in nerve excitation is totally unknown and does not offer, at present, any evidence for the possible mechanism of interaction between micro-waves and nerve membranes. 

Neumann, E. Nachmansohn, D. Katchalsky, A. An attempt at an integral interpretation of nerve excitability. Proc. Nat. 

Spiegel, R. J. Joines, W. T. A semiclassical theory for nerve excitation by a low intensity electromagnetic field. Bull. Math. Biophys., 1973, 35, 591-605. 

Example 12.10 Multiple steady states Multiple steady states and dissipative structures may play an important role in nerve excitations. Consider the following simple set of reactions ... 

These results provide additional evidence that enzyme repression is an important mechanism in B(a)P-induced neurotoxicity and likely results from oxidative stress in the nervous system. Inhibition of Na /K -ATPase, an important enzyme in muscle contraction and nerve excitability, in addition to decreased motor conduction velocities may explain the suppression of motor activity observed in B(a)P intoxicated rats (Kim et al, 2000 Saunders et al, 2001). Furthermore, there is also strong experimental evidence showing that oxidative stress and lipid peroxidative products can cause decreases in dopamine and inhibit Na /K -ATPase activity as well (Madrigal et al, 2003). 

He FS, Deng H, Ji X, et al. (1991) Changes of nerve excitability and urinary deltamethrin in sprayers. International Archives of Occupational and Environmental Health 62 587-590. 

He discovered and measured heat production associated with nerve impulses and analyzed physical and chemical changes associated with nerve excitation, among other studies. In 1922 he won the Nobel Prize in physiology or medicine (with otto meyerhof) for work on chemical and mechanical events in muscle contraction, such as the production of heat in muscles. This research helped establish the origin of muscular force in the breakdown of carbohydrates while forming lactic acid in the muscle. 

Effect on the Central Nervous System. Perfusion of the central nerve cord with 10 7 M avermectin eliminated the nerve excitation induced by y-BHC (10 6 M) (44). Within 15-20 min after perfusion of avermectin the nerve became completely calm. Under the experimental conditions a few random single spikes per minute were observed but only in the control nerves. Avermectin completely eliminated such background signals. Shortly before transmission blockage occurred, the nerve treated with y-BHC and avermectin showed severe but transient excitation. Recently Mellin et al. (49) observed an initial enhancement by avermectin of the facilitation response of excitatory postsynaptic potentials to a train of stimuli in the stretcher muscle of the lobster. Nerve excitation by DDT (10 5 m) was also found to be eliminated by avermectin (10 7 m). 

Calcium is the third most abundant metal (after Fe and Al) in the earth s crust and the fifth most abundant element in the body (after H, O, C, and N). Of all metal ions calcium, Ca, is undoubtedly most often referred to in the biochemical literature. The Ca ion plays a vital role in many processes in living systems including muscle contraction exocytosis cell fusion, adhesion, growth and motility blood cotting microtubule formation nerve excitability membrane transport of molecules intracellular communication hormonal responses biomineralization of bone and teeth photosynthesis immune reactions and enzymatic activation and control. A number of reviews and monographs are available " . 

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