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Cells, biological nerve

Nerve Cells. A nerve cell is also known as a neuron. It serves as the basic functional unit of the system. There are approximately 10 billion neurons in the human nervous system. In many ways, the neuron is just like any typical cell. It has a cell membrane and a nucleus. Its cytoplasm contains the usual organelles that you learned about in high school biology endoplasmic reticulum, mitochondria, storage vesicles, and the Golgi apparatus. [Pg.13]

Biochemistry is a dynamic, rapidly growing field, and the goal of this color atlas is to illustrate this fact visually. The precise boundaries between biochemistry and related fields, such as cell biology, anatomy, physiology, genetics, and pharmacology, are dif cult to define and, in many cases, arbitrary. This overlap is not coincidental. The object being studied is often the same—a nerve cell or a mitochondrion, for example—and only the point of view differs. [Pg.473]

Biological membranes show anisotropy, as their molecules are preferentially ordered in a definite direction in the plane of the membrane, and the coupling between chemical reactions (scalar) and diffusion flow (vectorial) can take place. Almost all outer and inner membranes of the cell have the ability to undergo active transport. Sodium and potassium pumps operate in almost all cells, especially nerve cells, while the active transport of calcium takes place in muscle cells. The proton pumps operate in mitochondrial membranes, chloroplasts, and the retina. [Pg.531]

Within cells, including nerve cells, fluxes of Ca ions play an important role in signal transduction (Chapter 11). Most eukaryotic cells export calcium across the plasma membrane or deposit it in membrane-enclosed storage sites in order to maintain free cytosolic Ca levels at 100—200 nM, roughly 10,000 times less than in the extracellular space. This allows calcium to function as a second messenger and also as a carrier of biological... [Pg.387]

A biological cell can be compared to a concentration cell for the purpose of calculating its membrane potential. Membrane potential is the electrical potential that exists across the membrane of various kinds of cells, including muscle cells and nerve cells. It is responsible for the propagation of nerve impulses and heart beat. A membrane potential is established whenever there are unequal concentrations of the same type of ion in the interior and exterior of a cell. For example, the concentrations of ions in the interior and exterior of a nerve cell are 400 mM and 15 mM, respectively. Treating the situation as a concentration cell and applying the Nemst equation, we can write... [Pg.775]

Electronic signals in nerve cells travel by means of metal-ion transport laterally in and out of the axon. Such transmembrane transport of ions is fundamental to cell biology, and attempts to mimic it artificially laid the foundation of supramolecular chemistry. Early studies in molecular recognition by Lehn in the 1970s explored the use of crown ethers as mimics of cyclic peptide ionophores like valinomycin, which bind cations selectively in their internal cavities. Natural ionophores act as antibiotics by upsetting the ionic balance across bacterial cell walls. [Pg.882]

The posterior lobe of the pituitary, ie, the neurohypophysis, is under direct nervous control (1), unlike most other endocrine organs. The hormones stored in this gland are formed in hypothalamic nerve cells but pass through nerve stalks into the posterior pituitary. As early as 1895 it was found that pituitrin [50-57-7] an extract of the posterior lobe, raises blood pressure when injected (2), and that Pitocin [50-56-6] (Parke-Davis) causes contractions of smooth muscle, especially in the utems (3). Isolation of the active materials involved in these extracts is the result of work from several laboratories. Several highly active posterior pituitary extracts have been discovered (4), and it has been deterrnined that their biological activities result from peptide hormones, ie, low molecular weight substances not covalendy linked to proteins (qv) (5). [Pg.187]

It is tempting to view ANNS as simplified versions of biological nervous systems. Yet even the most complex neurocomputers, with several million neurons, are unable to mimic the behavior of a fly, which has approximately one million nerve cells. This is because the nerve system of the fly has far more interconnections than are possible with current-day neurocomputers, and their neurons are highly specialized to perform necessary tasks. The human brain, with about 10 billion nerve cells, is still several orders of magnitude more complex. [Pg.8]

One form of biological poisoning mirrors the effect of lead on a catalytic converter. The activity of an enzyme is destroyed if an alien substrate attaches too strongly to the enzyme s active site, because then the site is blocked and made unavailable to the true substrate (Fig. 13.42). As a result, the chain of biochemical reactions in the cell stops, and the cell dies. The action of nerve gases is believed to stem from their ability to block the enzyme-controlled reactions that allow impulses to travel through nerves. Arsenic, that favorite of fictional poisoners, acts in a similar way. After ingestion as As(V) in the form of arsenate ions (As043 ), it is reduced to As(III), which binds to enzymes and inhibits their action. [Pg.690]

Tamplin et. al. (54) observed that V. cholerae and A. hydrophila cell extracts contained substances with TTX-like biological activity in tissue culture assay, counteracting the lethal effect of veratridine on ouabain-treated mouse neuroblastoma cells. Concentrations of TTX-like activity ranged from 5 to 100 ng/L of culture when compared to standard TTX. The same bacterial extracts also displaced radiolabelled STX from rat brain membrane sodium channel receptors and inhibited the compound action potential of frog sciatic nerve. However, the same extracts did not show TTX-like blocking events of sodium current when applied to rat sarcolemmal sodium channels in planar lipid bilayers. [Pg.82]

V. G. Dethier, in R. G. Grenell and L. J. Mullins (Eds.), Molecular Structure and Functional Activity of Nerve Cells, American Institute of Biological Sciences, Arlington, VA, 1956, pp. 1-35. [Pg.248]

In medical practice, methods and instruments relying on electrochemical principles are widely nsed in diagnosing various diseases. The most important ones are electrocardiography, where the transmembrane potential of the muscle cells during contraction of the heart mnscle is measured, and electroencephalography, where impulses from nerve cells of the brain are measured. They also include the numerous instruments nsed to analyze biological fluids by electrochemical methods (see also Section 30.3). [Pg.411]


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See also in sourсe #XX -- [ Pg.489 , Pg.490 ]




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Nerve cells

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