Graded potentials

Graded potentials are short-distance signals (see Table 4.1). They are local changes in membrane potential that occur at synapses where one neuron 

Magnitude of signal dissipates as it moves away from the site of stimulation 

Initiated at synapses (where one neuron comes into contract with another) 

Signal travels by local current flow or by saltatory conduction 

Magnitude of signal is maintained along entire length of neuron 

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Compare and contrast graded potentials and action potentials... 

Table 4.1 Distinguishing Features of Graded Potentials and Action Potentials Graded potentials Action potentials...

Figure 5.1 Mechanism of action at a chemical synapse. The arrival of an action potential at the axon terminal causes voltage-gated Ca++ channels to open. The resulting increase in concentration of Ca++ ions in the intracellular fluid facilitates exocytosis of the neurotransmitter into the synaptic cleft. Binding of the neurotransmitter to its specific receptor on the postsynaptic neuron alters the permeability of the membrane to one or more ions, thus causing a change in the membrane potential and generation of a graded potential in this neuron.

As previously mentioned, a single action potential at a single synapse results in a graded potential only an EPSP or an IPSP. Therefore, generation of an action potential in the postsynaptic neuron requires the addition or summation of a sufficient number of excitatory inputs to depolarize this neuron to threshold. Two types of summation may occur ... 

Data collection and communication in the nervous system occurs by means of graded potentials, action potentials, and synaptic coupling of neurons. These electrical potentials may be recorded and analyzed at two different levels depending... 

A. Gossard, M. Sundaram, and P. Hopkins, Wide Graded Potential Wells... 

Nerve conduction action potential, -+ graded potential... 

Electrolytic Oxidation I. Electrode Potential.—A series of stable potentials is difficult to obtain at an anode in the presence of a depolarizer the potential generally rises rapidly from the low value, at which the anode dissolves, to the high value for passivity and oxygen evolution. Since a platinum electrode is nearly always passive, however, it is possible to obtain graded potentials to a limited extent the data quoted in Table LXXXVI were recorded for the oxidation of an acid solution of... 

The impact of particle size on the dissolution performance was also observed for amorphous ITZ Soluplus extrudates. Samples of defined sieve fractions as well as samples of the unmilled strands were compared (simulated gastric fluid, n=6). The results (Fig. 13.1 data not published) clearly showed that after 100 min, the API from milled particles with a mean particle size above 250 xm was fully dissolved, whereas the dissolution from finer particles was significantly slower and incomplete. The unmilled strands were steadily eroding resulting in almost 100 % dissolution after 330 min. For this formulation, coarser particles were more beneficial fhan finer grades, potentially as a result of polymer swelling or concurrent recrystallization effects. 

As early as 1908, Sand (4) determined antimony in a variety of media by controlled-potential deposition using a manually-controlled graded potential device. Most commonly, antimony is deposited as the metal on platinum electrodes from solutions of antimony (III) although antimony has also been deposited at mercury cathodes for separation purposes (5). Care must be taken to avoid hydrogen evolution or some antimony may be lost as the hydride (stibine), especially at elevated temperatures (6). 

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