Asked by: Zeltia De Bellamedical health brain and nervous system disorders
Why does the amplitude of the compound action potential increase with increasing stimulus strength?
Last Updated: 26th February, 2020
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Then, why does the peak of a compound action potential increase with greater stimulus strength?
As stimulus strength increases, more and more individual axons are excited until eventually all of the axons in the nerve are excited. This resulted in the peak of the compound action potential increasing as mire individual action potentials are generated.
why did the amplitude of the action potential did not increase as stimulation voltage increased above threshold? The amplitude did not increase because no matter what the voltage is applied, once the membrane reaches threshold the action potential will still be the same size. The membrane potential between the axon hillock and axon changed with threshold because the potential was graded and no action potential was generated.
Similarly, you may ask, why do the action potential tracings increase in amplitude when the stimulus strength is increased?
Continue increasing the voltage above threshold by 0.1-0.2 V increments. Notice that as you increase the stimulus strength, the amplitude of the action potential increases slightly (Fig 6.12). This is because the stimulus strength is now strong enough for all the neurons in the nerve to undergo action potential.
What affects the amplitude of an action potential?
The amplitude of the action potential is mainly dependent on the influx of Na+. In addition, temperature affects action potential amplitude (Hodgkin & Katz, 1949) and slight temperature differences along long axons may therefore be expected to alter amplitude. Likewise, shape may alter as well.