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EADs most commonly originate in mid-myocardial cells and Purkinje fibers, but can develop in other cardiac cells that carry an action potential. Phase 2 may be interrupted due to augmented opening of calcium channels, while phase 3 interruptions are due to the opening of sodium channels .
Factors promoting the differentiation of M cells have yet to be elucidated, but they are thought to develop in response to signals from immune cells found in developing Peyer's patches. [4] B cells have been implicated in the developmental of M cells, since they are also localized in high numbers in the follicular-associated epithelium (FAE).
Several types of cells support an action potential, such as plant cells, muscle cells, and the specialized cells of the heart (in which occurs the cardiac action potential). However, the main excitable cell is the neuron , which also has the simplest mechanism for the action potential.
Cells with a defective G 2-M checkpoint will undergo apoptosis or death after cell division if they enter the M phase before repairing their DNA. [1] The defining biochemical feature of this checkpoint is the activation of M-phase cyclin-CDK complexes, which phosphorylate proteins that promote spindle assembly and bring the cell to metaphase. [2]
The process of depolarization is entirely dependent upon the intrinsic electrical nature of most cells. When a cell is at rest, the cell maintains what is known as a resting potential. The resting potential generated by nearly all cells results in the interior of the cell having a negative charge compared to the exterior of the cell.
The sodium-calcium exchanger (often denoted Na + /Ca 2+ exchanger, exchange protein, or NCX) is an antiporter membrane protein that removes calcium from cells. It uses the energy that is stored in the electrochemical gradient of sodium (Na +) by allowing Na + to flow down its gradient across the plasma membrane in exchange for the countertransport of calcium ions (Ca 2+).
M current is a type of noninactivating potassium current first discovered in bullfrog sympathetic ganglion cells. [1] The M-channel is a voltage-gated K+ channel (Kv7/KCNQ family) that is named after the receptor it is influenced by. The M-channel is important in raising the threshold for firing an action potential.
T-tubules (transverse tubules) are extensions of the cell membrane that penetrate into the center of skeletal and cardiac muscle cells.With membranes that contain large concentrations of ion channels, transporters, and pumps, T-tubules permit rapid transmission of the action potential into the cell, and also play an important role in regulating cellular calcium concentration.