Conduction of Electrical Impulses - Resting Potential

Resting potential

the potential difference across their cell surface, present in inactive neurons

potential difference

-70mV

how does this potential difference arise

• unequal distribution of sodium and potassium ions

polarized membrane

when its in a resting potential

electrochemical gradient

• conc gradient across the membrane

sodium potassium pumps

• use ATP

• pump 2K into cell for every 3 Na out

ion leak channels

• passive movement of Na+ and K+

• cell membrane is more permeable to K+ then Na+, so K+ diffuses out of cell more

voltage-gated sodium and potassium channels

• open and close when theres a change in membrane potential (voltage)

• mainly closed at resting potential

How is a resting potential maintained

1. in the axoplasm (cytoplasm of axon) there is a high K+ and low Na+ conc, in contrast to the outside which is low K+ and high Na+

2. using ATP a sodium potassium pump, pumps 3Na+ in and 2k+ OUT

3. however, eventually the pump would run out of ions to pump, so passive diffusion of Na+ into the cell and K+ OUT of the cell against their conc gradient occurs thru ion leak channels

4. membrane is 20x more permeable to K+, so more K+ is lost then Na+ is gained, this leaves behind lots of CL- which cant leave

5. thus a -70mV charge