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| Description: Alterations in neuromuscular activity caused by changes in free, ionized calcium levels. The lipid bilayer in nerve or muscle cell membranes with a sodium channel is shown on the left. Normally, during an action potential, the sodium channel would open, allowing sodium to rush into the cell, causing depolarization. Free, ionized calcium can occupy space in the extracellular portion of the sodium channel, thereby interfering with sodium entry. The more free calcium is available, the greater the degree of obstruction of the sodium channels. Acidosis results in increased levels of free calcium, which impairs sodium entry into nerve and muscle cells and decreases neuromuscular excitability. Alkalosis results in decreased levels of free calcium, which results in more sodium entry into nerve and muscle cells, increasing neuromuscular excitability. A lipid bilayer formed by round cells with long tail like strands emitting from them, is cut by a sodium channel. Ionized calcium and sodium enter the channel from the extracellular fluid around the layer. Picture Stats: Views: 22 Filesize: 118.71kB Height: 662 Width: 925 Source: https://biology-forums.com/index.php?action=gallery;sa=view;id=49810 |