top of page

 NATURE OF NERVE SIGNALS 

Overview

  • As with all cells there is an ELECTRIC CHARGE difference across their plasma membrane 

    • This MEMBRANE POTENTIAL exists due to a different concentration of ions inside the membrane​ than outside (more anions therefore, negative charge in the membrane)

    • This causes the membrane to become polarized 

​

  • A neuron in its resting state NOT transmitting an electrical signal has a potential of -70mV known as resting potential. 

  • A change in this voltage will cause an electric impulse and these changes are made possible by ion channels or gates which allow ions to either enter or leave the membrane, causing changes to the membrane potential 

  • Gates open and close in response to stimuli

How An Electrical Impulse Is sent 

Transmission of Nerve Impulses:

  • Concentration of SODIUM IONS is greater outside the axon than inside whereas, the concentration of POTASSIUM IONS is greater inside the axon than outside

  • This unequal distribution of ions is caused by the sodium-potassium pump

  • Using active transport (ATP) sodium ions are pumped out and potassium ions are pumped into the axon

  • For a neuron to create an impulse a MINIMUM THRESHOLD must be met which is known as the "ALL OR NONE" response 

    • If the stimulus is strong enough to reach this threshold, then sodium ions are able to rish outside into the axoplasm

    • This causes DEPOLARIZATION in the region of the stimulus and increases voltage in the axon to +40 mV

    • DEPOLARIZATION is the rush of positive ions into the axon which increase the voltage from -70 to +40 mV in the axon.

  • Next, the sodium gates close and potassium gates open and this causes K+ ions to rush out of the axoplasm, causing repolarization to occur 

  • Then REPOLARIZATION occurs as positive ions rush out of the axon the voltage in the axon decreases from +40 to -70 mV 

  • ​As the potassium gates are relatively slow to close the voltage inside the axon decreases below the resting state 
    • This is called the RECOVERY PERIOD and during this the axon is unable to conduct a nerve impulse 
    • Sodium-potassium pump activities and begins to restore the voltage back to -70 mV as Na+ is pumped out and K+ is pumped back into the axon
  • Depolarization and repolarization of the membrane is a positive feedback cycle that occurs constantly

bottom of page