Question

What is the process of having a nerve impulse?

Answer 1

The actual process of nerve impulse consists of firing of neuron from one end to another as a result of electric change that occurs across the membrane. The membrane in post firing stage is polarized with excesof sodium ions outside (Na+) outside whie excess of potassium ions(K+) inside this is konwn as resting potential (at about -70 millivolts). During the firing of neuron (caused by any stimulus like: light, sound, heat, mechanical pressure, and chemicals etc.) there is change in charge and a graded potential occurs when the stimulus causes Na and K ions to open their channels. In this phase , if the sodium ions enter the membrane gets depolarized. while if the potassium ions enter the membrane gets hyperpolarized (gets more negative in charge).

Overall the process can be described in four steps:

• Action potential- if the stimuli is long enough it might create an impulse long enough so that the flow of charge in Na+ ions occurs, which inturn stimulates neighbouring neuron and the charge travel from one neuron to another. It works on all-or-none level, when stimulus is not long enough it depolarises.
• Repolarization-in response to Na+ ions, K+ channels open, causing K+ ions to move out. once the K+ ions are open, Na+ gates are closed.
• Hyperpolarization- it occurs when K+ ions have moved out to maintain the balance causing the external partof the membrane to get hyperpolarized (at about -80millivolts).
• Refractory period- it occurs when both Na+ and K+ sides are in unusual state of being in wrong direction. At this time axon does not react to any new stimulus. To esablish the original distribution Na+ and K+ ions return to their originalal state in the cell membrane.

Once the ions return to their original place, the neuron can fire on presence of another stimuli.