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Renin Angiotensin Mechanism.

Electrophysiology of Neurons: Action Potential.

 Electrophysiology of Neurons: Action Potential

ELectrophysiology of Neurons:

  • The intracellular and extracellular fluid in the nervous system contains many charged ions like Na+, K+, Ca++, Cl- etc.

  • The presence of these ions imparts an electric potential inside the cell and outside the cell.

  • Membrane Potential (Transmembrane Potential, Membrane Voltage) is the difference of voltage between inside the cell membrane and outside the cell membrane.

  • The resting membrane potential is -70mv.

  • Nerve impulse (Action Potential) is generated by a change in ion concentrations across the cell membrane. 

  • The three phases in which action potential takes place are,

    1. Depolarization.

    2. Repolarization

    3. Hyperpolarization. 

  1. Depolarization:

  • On a receiving stimulus the Na+  ion channels open causing entry of Na+ ions inside the cell.

  • As Na+ ions are positively charged, the resting membrane potential now starts shifting to “0”.

  • When the membrane potential reaches “-55mv” it is said that the “Action Potential is generated or threshold is generated”.

  • Due to the higher concentration gradient of Na+  ions the membrane potential reaches upto “+30mv”.

  • Depolarization means shifting of membrane potential from” -70mv to 0”.

  1. Repolarization:

  • As the membrane potential reaches “+30mv” it causes the opening of “K+” ion channels.

  • The K+ ions start leaving the cell to extracellular fluid ( Concentration of K+ ions is less outside the cell).

  • The loss of K+  ions causes the membrane potential to come down.

  • The opening of K+ ion channels is slower at the same time the Na+ ion channels start getting inactivated.

  • Due to this the membrane potential drops to its resting stage i.e -70mv.

  • The return of membrane potential to -70 mv is called “Repolarization”.

  1. Hyperpolarization:

  • Due to the slow closing of K+ ion channels the further loss of positivity the membrane potential lowers more to -90mv.

  • Hyperpolarization means dropping of membrane potential to -90mv.

  • After closing of K+ ion channels the membrane potential comes back to its resting stage and is now ready to receive new stimulus.


Commonly Asked Questions:

  1. Write a short note on “Electrophysiology of Neuron”.

  2. What is action Potential? Discuss different phases of action potential.
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