local currents

• the opening of sodium ion channels at one particular point of the neuron upsets the balance of the sodium and potassium ions set up by the action of the sodium/potassium pumps. When sodium ions are allowed to flood into the neuron to cause depolarisation, this creates a local current in the cytoplasm of the neuron. These local currents cause a slight depolarisation of the membrane causing sodium ion channels further along the membrane to open due to positive feedback.
• what is the first step in the formation and transmission of a local current?

  when an action potential occurs, the sodium ion channels open at that point in the neuron
• what is the second step in the formation and transmission of a local current?

  The open sodium ion channels allow sodium ions to diffuse across the membrane from the region of high concentration outside the neuron into the neuron. The concentration of sodium ions inside the neuron rises at the point where the sodium ion channels are open.
• what is the third step in the formation and transmission of a local current?

  Sodium ions continue to diffuse sideways along then neuron, away from the region of increased concentration,- creating a local current.
• what is the fourth step in the formation and transmission of a local current?


  The local current causes a slight depolarization further along the neuron which affects voltage-gated sodium ion channels and makes them open. The open channels allow a rapid influx of sodium ions which causes a full depolarisation further along the neuron- the action potential will move along then neuron as a result.