Action potentials & nerve impulses

1) In a neurones resting state, the outside of the membrane is positievly charged compared to the inside. Cause by more positive ions outside the cell than inside. 

2) This therefore means the membranes polarised - A difference in charge (Potential difference or volatage) accross it.

3) The voltage accross the membrane at rest is called the resting potential -70mV 

4) The resting potential is created and maintained by sodium-potassium pumps and potassium ion channels in a neurones membrane.

• The sodium-potasium pumps move sodium ions out of the neurone. Due to the memrane not being permiable, the sodium ions cannot diffuse back in.   This creates a sodium ion electrochemical gradient - More positive sodium ions outside the cell than in.
• The sodium-pottasium pumps also move potassium ions into the neurone. Due to the membrane being permiable to potassium ions, they diffuse back out through potassium ion channels. 
• This makes the outside of the cell positievly charged compaired to the inside.