Action Potential Essay

Neurons communicate over long distances using action potentials. Action potentials occur as a result of rapid changes in membrane permeability. Resting membrane potential of a cell is approximately -70 millivolts. Large anions trapped inside the cell, negatively charged proteins, as well as a higher concentration of positively charged ions outside than inside are some of the factors that contribute to the initial negative charge within the cell at resting value. Ion concentration gradients as well as membrane permeability to ions can affect resting membrane potential. Cells expend a great deal of energy in order to maintain a higher concentration of K+ inside the cell and a higher concentration of Na+, Cl-, and Ca++ outside the cell. While at rest, K+ can …show more content…
When the action potential reaches its peak of 30 millivolts, Na+ channels close. Repolarization begins as K+ voltage gated channels start to open and an efflux of K+ are driven out of the cell due to the electrochemical gradient. With less Na+ inside the cell and more K+ outside the cell, the membrane potential begins to decline toward its resting value. Resting value is reached, yet K+ voltage gated channels remain open allowing additional K+ to move out. Hyperpolarization is activated when the K+ gates finally close and the membrane potential is now more negatively charged than at resting value due to the imbalance of ions inside and outside the cell. Following inactivation of K+ gates, the Na+/K+ pump moves Na+ out and K+ in, restoring the gradient and resting membrane potential. The action potential fires. In an unmyelinated axon, Na+ flow in and cause adjacent areas to depolarize to threshold, sending the action potential slowly down the axon. Conversely, the conduction rate of an action potential is much faster in a myelinated axon. Since ions will not travel across myelin, a separate area must be utilized to permit the conduction of the action potential. At the Nodes of Ranvier,