The human body is a fascinating array of mechanisms, each perfectly sculpted to satisfy its role in the ever changing needs of our physiology. The various systems within us each rely on impulses, sent via the central or peripheral nervous systems, to coordinate everything from breathing to walking to thinking. These messages, sent throughout the entire body and relayed through neurons, consisting of axons and dendrites, are just as intricate as the systems they support.
[...] Figure Legend: A side view of a voltage operated paddle in a potassium channel in the S3- S4 domain. (http://www.sciencemag.org/cgi/content/full/306/5700/1304) The voltage sensor paddles hold four positive charges, making the total sixteen, which slide almost all the way through the fluid membrane. This motion slides the charges from the interior side of the membrane to the exterior, as the situation dictates. With the charge at the cell exterior end of the membrane, the channel remains open to let out ions, however as soon as current through the membrane changes back to negative, or resting potential of around -70 mv, the gates close again and await the next depolarization. [...]
[...] Figure Legend: Two of the helical subunits of a voltage gated potassium channel, along with carbonyl binding sites at the top, which is the narrowest region of the channel Nanolake When an action potential occurs in a cell, current propagates quickly along its membrane, which does not allow for the casual passage of charged molecules. To allow for permeability in order to restore resting potential, the voltage gated potassium channel includes, as the name suggests, a voltage operated This gate consists of four paddles, known as “voltage sensor paddles”, with flexible hinges which are extremely sensitive to voltage changes, even when compared to a modern transistor, as illustrated in Figure 3 below. [...]
[...] The helical subunits, with their respective carbonyl binding sites in the narrow pore region, as well as the voltage sensitive gates contribute to the explanation of the apparent paradox between high conductivity and permeability, however the sodium ion's smaller radius and consequently its free energy difference of about 18 kcal/mol with potassium ions is the determining factor in the channels selectivity (Noskov and Roux). This selectivity allows for the cell to return to its resting potential of -70mv after a spike with the outflow of potassium ions along their concentration gradient and as a result allows for the normal operations of all the physiological systems that we take for granted on a daily basis. [...]
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