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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).
Depolarization propagates through cardiac muscle very rapidly. Cells of the ventricles contract nearly simultaneously. The action potentials of cardiac muscle are unusually sustained. This prevents premature relaxation, maintaining initial contraction until the entire myocardium has had time to depolarize and contract. Absence of tetany.
(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 ...
A nerve impulse causes Na + to enter the cell, resulting in (b) depolarization. At the peak action potential, K + channels open and the cell becomes (c) hyperpolarized. Voltage gated ion channels respond to changes in the membrane potential. Voltage gated potassium, chloride and sodium channels are key components in the generation of the action ...
This electrical polarization results from a complex interplay between protein structures embedded in the membrane called ion pumps and ion channels. In neurons, the types of ion channels in the membrane usually vary across different parts of the cell, giving the dendrites , axon , and cell body different electrical properties.
Because voltage is by definition a bipolar measurement between two points, describing an electrocardiographic lead as "unipolar" makes little sense electrically and should be avoided. The American Heart Association states "All leads are effectively 'bipolar,' and the term 'unipolar' in description of the augmented limb leads and the precordial ...
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 ...