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Depolarization is essential to the function of many cells, communication between cells, and the overall physiology of an organism. Action potential in a neuron, showing depolarization, in which the cell's internal charge becomes less negative (more positive), and repolarization, where the internal charge returns to a more negative value.
A neuron receives signals from neighboring cells through branched, cellular extensions called dendrites.The neuron then propagates an electrical signal down a specialized axon extension from the basal pole to the synapse, where neurotransmitters are released to propagate the signal to another neuron or effector cell (e.g., muscle or gland).
Since basal and lateral membranes share the same determinants, another mechanism must make the difference between the two domains. Cell shape and contacts provide the likely mechanism. Lateral membranes are the site of contact between epithelial cells, whereas basal membranes connect epithelial cells to the basement membrane , an extracellular ...
(A brief chemical gradient driven efflux of Na+ through the connexon at peak depolarization causes the conduction of cell to cell depolarization, not potassium.) [27] These connections allow for the rapid conduction of the action potential throughout the heart and are responsible for allowing all of the cells in the atria to contract together ...
Furthermore, it can be used to identify characteristics of significant medical conditions through comparing the effects of those conditions on threshold potential with the effects viewed experimentally. For example, ischemia and depolarization cause the same "fanning in" effect of the electrotonus waveforms. This observation leads to the ...
This inward flow of sodium leads to a short term depolarization of the postsynaptic neuron and an EPSP. While a single depolarization of this kind may not have much of an effect on the postsynaptic neuron, repeated depolarizations caused by high frequency stimulation can lead to EPSP summation and to surpassing the threshold potential. [9]
Ion channels, which are specific in which ions are allowed to pass through them, are also crucial to polarization and maintaining polarization. Voltage-gated ion channels activate or deactivate in response to changes in membrane potential, allowing various ions to flow down their concentration gradient according to the channel's specificity.
There are important physiological differences between nodal cells and ventricular cells; the specific differences in ion channels and mechanisms of polarization give rise to unique properties of SA node cells, most importantly the spontaneous depolarizations necessary for the SA node's pacemaker activity.