Sodium/Potassium ATPase pumps create more positively charged ions outside the cell than inside the cell, this creates a relative negative charge in the cell
Phase 4- Resting (~ -90 mv)
Phase 0- Sodium enters the cell (+10 mv)
Phase 1- Potassium efflux from cell as now there is no negative charge holding it in (0 mv)
Phase 2- Calcium channels open and allow calcium in, calcium triggers the ryandoine receptor and allows for calcium dependent calcium release from the sarcoplasmic reticulum occurs
Phase 3- Potassium continues to leave the cell allowing return to -90 mv
