Action Potential Self Propagates Along The Cell Essay

Action Potential Self Propagates Along The Cell Essay

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Action potential self-propagates along the cell, and creates a domino effect, stimulating other channels to open (Marieb & Hoehn, 2013, p.404). At a resting state, leak channels are the only channels that are open. Nevertheless, depolarisation occurs, meaning that the inside of the cell changes from negative to positive, only happens when other channels like voltage gated channel opens (Marieb & Hoehn, 2013, p.400). Voltage channel is a protein channel that opens when there is a voltage change (Marieb & Hoehn, 2013, p.401). Although, this gated channels will only open when it reaches a threshold. A threshold is when a nerve impulse reaches a level between -55 and -50mV. Thus, threshold causes Na + influx into the cell (Marieb & Hoehn, 2013, p.401). As a result, depolarisation occurs, and the resting potential becomes less negative, and the outside becomes negative. Furthermore, there is a “sharp upward spike of the action potential” (Marieb & Hoehn, 2013, p.401), see appendix A. This upward spike reaches +30mV, and a rapid diffusion of Na+ ions due to a low concentration gradient of Na+ ions inside the cell, and the anionic proteins attracts positive charges (Marieb & Hoehn, 2013, p.401). Once, depolarisation reaches +30mV, the Na+ channels closes and Na+ ions stops entering the cell. Furthermore, neurons are unresponsive to other stimulus no matter its electrical intensity, this is known as absolute refractory period (Marieb & Hoehn, 2013, p.405). The K+ voltage gated channels opens and K+ diffuses out. This reverts back to its resting state, it repolarises (Marieb & Hoehn, 2013, p.401). However, hyperpolarisation happens because of the slow gated K+ channels. This causes and excess K+ ions outside the cell, and makes a shallow c...

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...d out of the cell. Furthermore, Na+ and K+ pump keeps the inside of the cell polarised or ionically imbalanced (Marieb & Hoehn, 2013, p.407). A change of membrane potential is caused by a nerve cell stimulation. Thus, the action potential activity occurs and works in a cycle, from resting to excited and back to its original state (Marieb & Hoehn, 2013, p.407). This activity allows neurons to communicate with each other to do a task, but when a neurotoxin enters the body, it can disrupt its normal function. For instance, TTX is a neurotoxin that disrupts action potential by binding into the neuroreceptors of Na+ voltage gated channel (Ruben & Lee, 2008, p. 407). As a result, TTX inactivate the channel, unable to reach threshold. Moreover, TTX is found from the gonads and liver of a puffer fish, and suggest that proper cooking techniques can avoid consuming the toxin.

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