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However, the main excitable cell is the neuron, which also has the simplest mechanism for the action potential. [citation needed] Neurons are electrically excitable cells composed, in general, of one or more dendrites, a single soma, a single axon and one or more axon terminals. Dendrites are cellular projections whose primary function is to ...
Like all animal cells, the cell body of every neuron is enclosed by a plasma membrane, a bilayer of lipid molecules with many types of protein structures embedded in it. [12] A lipid bilayer is a powerful electrical insulator, but in neurons, many of the protein structures embedded in the membrane are electrically active. These include ion ...
In non-excitable cells, and in excitable cells in their baseline states, the membrane potential is held at a relatively stable value, called the resting potential. For neurons, resting potential is defined as ranging from –80 to –70 millivolts; that is, the interior of a cell has a negative baseline voltage of a bit less than one-tenth of a ...
The polarization of cellular membranes are established and maintained through the active and passive transport of ions across the membrane through membrane proteins, specifically channel proteins and ion pumps. These proteins maintain an electrochemical gradient by pumping certain ions in and out of the cell.
Cell membranes are generally impermeable to ions, thus they must diffuse through the membrane through transmembrane protein channels. Voltage-gated ion channels have a crucial role in excitable cells such as neuronal and muscle tissues, allowing a rapid and co-ordinated depolarization in response to triggering voltage change.
Ion channels are located within the membrane of all excitable cells, [3] and of many intracellular organelles. They are often described as narrow, water-filled tunnels that allow only ions of a certain size and/or charge to pass through. This characteristic is called selective permeability.
An alpha subunit forms the core of the channel and is functional on its own. When the alpha subunit protein is expressed by a cell, it is able to form a pore in the cell membrane that conducts Na + in a voltage-dependent way, even if beta subunits or other known modulating proteins are not expressed. When accessory proteins assemble with α ...
Each cell of the automaton is made to represent some section of the medium being modelled (for example, a patch of trees in a forest, or a segment of heart tissue). Each cell can be in one of the three following states: Traveling waves in a model of an excitable medium (White – Quiescent, Green – Excited, Yellow – Refractory)