Editing Pacemaker potential (section)

==Induction==
The firing of the pacemaker cells is induced electrically by reaching the threshold potential of the cell membrane. The [[threshold potential]] is the potential an excitable cell membrane, such as a [[myocyte]], must reach in order to induce an action potential.<ref>{{cite book
  | last = Campbell
  | first = Neil. A
  | title = Biology
  | url = https://archive.org/details/biologycamp00camp
  | url-access = registration
  | publisher = Benjamin Cummings
  | year = 1996
  | page = G–21
  | isbn = 978-0-07-366175-9
}}</ref> This [[depolarization]] is caused by very small net inward currents of calcium ions across the cell membrane, which gives rise to the action potential.<ref name="pmid19181406">{{cite journal |last1=Verkerk |first1=Arie O. |last2=van Ginneken |first2=Antoni C.G. |last3=Wilders |first3=Ronald |title=Pacemaker activity of the human sinoatrial node: Role of the hyperpolarization-activated current, If |journal=International Journal of Cardiology |date=March 2009 |volume=132 |issue=3 |pages=318–336 |doi=10.1016/j.ijcard.2008.12.196 |pmid=19181406 }}</ref><ref>{{cite book
  | last = Boron
  | first = Walter. F
  |author2=Emile Boulpaep
  | title = Medical Physiology
  | publisher = Elsevier Saunders
  | year = 2003
  | page = 487
  | isbn = 978-0-7216-0076-5
}}</ref>