The<unk>  (or If, or IKf, also referred to as the funny<unk>  is an electric<unk>  in the heart that flows through the HCN channel or<unk>  channel. Such channels are important parts of the electrical conduction system of the heart and form a component of the natural<unk> . First described in the late 1970s in Purkinje fibers and sinoatrial myocytes, the cardiac<unk>  "funny" (If)<unk>  has been extensively characterized and its role in cardiac pacemaking has been investigated. Among the unusual features which justified the name "funny" are mixed Na+ and K+ permeability, activation on hyperpolarization, and very slow kinetics.
Pacemaker current
Cardiac action potential
VA conduction
QRS complex
End-plate potential
QT interval
QT interval variability
PR interval