The Action Potential Essay

An action potential is when neurons connect via long distances by producing and sending an electrical signal. The action potential begins at the soma, more specifically, the axon hillock, where the density of the voltage gated sodium channels are high. The action potential starts when it receives signals from the dendrites and cell body. An important aspect of the axon transporting electrical signals to the axon terminal is the speed of the nerve. It needs insulation to prevent the escape of electrical energy during the action potential transmission. This affects the speed of the nerves impulses transmission. A myelin sheath is formed with small segments that are interrupted by intervals called the Nodes of Ranvier. The ion exchange will be facilitated.
After the nerve cell is at it's resting state, the threshold is typically between -50 and -70 mV in relation outside the cell. The concentration of sodium is much higher outside the cell whereas there is higher concentration in potassium ions inside the nerve cell. The dendrites and cell body reach the axon hillock and cause membrane potential to become more positive. This process is called depolarization. Sodium travels down to it's electrochemical gradient into the cell. As the axon hillock depolarizes, voltage gated sodium channels open rapidly, and causes sodium to increase the rate of flow. The sodium channels begin to close.
The potassium voltage gated channels begin slowly to respond to depolarization and open when the action potential reaches at it's highest. The positive feedback loop is now broken and ends the stage of the action potential rising. The potassium leaves the cell and finally enter the potassium voltage gated cells. With less sodium into the cell, and more potassium is moving out. The membrane potential becomes more negative, working to its resting place. This process is then called repolarization.
In the neurons, the voltage gated potassium channels stay open after the cell is repolarize. The potassium ions move out the cell, producing the membrane potential to become more negative than the resting membrane potential. This is called hyperpolarization.
The sodium-potassium pump travels the sodium out of the cell and the potassium into the cell against their concentration gradients. In addition to the voltage gated potassium and sodium channels, a leak channel occurs. The sodium and potassium move through the cell membrane below to their gradients from a high concentration to a lower concentration. After the neuron generates its action potential, it cannot produce another one. The sodium channels are inactive and it will not open no matter what voltage is applied to the membrane. The potassium channels are open at this point and an absolute refractory period occurs. Immediately after the absolute refractory period occurs, the cell can finally make an action potential, only when it is depolarized to a value more positive than the normal threshold. This will occur because some sodium channels are still inactive and some potassium channels begin the positive feedback loop. This leads to a relative refractory period.