Transient depolarization

Kang N, Xu J, Xu Q, Nedergaard M, Kang J (2005) Astrocytic glutamate release-induced transient depolarization and epileptiform dischaiges in hippocampal CAl pyramidal neurons. J Neurophysiol... 

The transient change in the transmembrane potential upon excitation. An action potential cycle consists of a transient depolarization of the cell membrane of an excitable cell (such as a neuron) as a result of increased permeability of ions across the membrane, followed by repolarization, hyperpolarization, and finally a return to the resting potential. This cycle typically lasts 1-2 milliseconds and travels along the axon from the cell body (or, axon hillock) to the axonal terminus at a rate of 1-100 meters per second. See Membrane Potential... 

Excitatory synaptic potentials and spike generation. The figure shows a resting membrane potential of-70 mV in a postsynaptic cell. Stimulation of an excitatory pathway (E) generates transient depolarization. Increasing the stimulus strength (second E) increases the size of the depolarization, so that the threshold for spike generation is reached. 

Kang, N., Xu, J., Xu, Q., Nedergaard, M., and Kang,J. (2005). Astrocytic glutamate release-induced transient depolarization and epileptiform discharges in hippocampal CA1 pyramidal neurons. 

Two distinct receptor groups have been identified for acetylcholine, the nicotinic and the muscarinic groups (Table 11.1). Furthermore, there are at least four subtypes of nicotinic and five subtypes of muscarinic receptors. Nicotinic receptors are ubiquitous and exist at the neuromuscular junctions of skeletal muscles and on ganglion cells in the autonomic nervous system. Nicotinic receptors located on cation-specific ion channels, when opened, evoke fast, transient depolarizations of the recipient cell. Muscarinic receptors are found in smooth muscle receiving parasympathetic innervation and elsewhere, and can be blocked by atropine. Muscarinic receptors are coupled indirectly to slow and fast ion channels via G proteins. 

We have seen that sodium enters the cells, but potassium is set free into the extracellular space where it induces irregular depolarizations, particularly in the surroundings of an ischemic focus. Such transient depolarizations travel over the cortex like classical waves of spreading depression of electrical activity (Back et al. 1994b Leao 1944 Nedergaard and Astrup 1986). The number of such peri-infarct depolarizations (PIDs) correlated well with final... 

Figure 13.13 Action potential. Signals are sent along neurons by the transient depolarization and repolarization of the membrane.

A EXPERIMENTAL FIGURE 7-30 Recording of an axonal membrane potential over time reveals the amplitude and frequency of action potentials. An action potential is a sudden, transient depolarization of the membrane, followed by repolarization to the resting potential of about -60 mV. The axonal membrane potential can be measured with a small electrode placed into it (see Figure 7-14). This recording of the axonal membrane potential in this neuron shows that it is generating one action potential about every 4 milliseconds. 

The action potential is a wave of transient depolarization that travels along the membrane of a nerve cell (or any other kind of excitable cell, such as a muscle cell) as a result of the movements of ions across the membrane. (Figure 10.31). 

Fang Z, Mortimer JT (1991) A method to effect physiological recruitment order in electrically activated muscle. IEEE Trans Biomed Eng 38(2) 175-179 Grill WM, Mortimer JT (1997) Inversion of the current-distance relationship by transient depolarization. IEEE Trans Biomed Eng 44 (l) 001-009... 

Equation (30) has been normalized by the anisotropy at zero concentration. Thus, transient depolarization experiments provide a direct test of a transport theory, and useful information can be extracted from experiments performed at a single sample concentration. In terms of the steady state anisotropy r we may write... 

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