Amplitude of action potential is predominantly determined by

Impermeant Negatively Charged Ions (Anions) Inside the Nerve Axon. Inside the axon are many negatively charged ions that cannot go through the membrane chan- nels. They include the anions of protein molecules and of many organic phosphate compounds, sulfate compounds, and so foh. Because these ions cannot leave the interior of the axon, any deficit of positive ions inside the membrane leaves an excess of these impermeant negative anions. Therefore, these impermeant negative ions are responsible for the negative charge inside the fiber when there is a net deficit of positively charged potassium ions and other posi- tive ions. Chlorine is the most common impermeant negative charge in the axon membrane Ref guyton and hall textbook of medical physiology 12/e p64