If (funny) channels in the sino-atrial node
Last reviewed 09/2021
- pacemaker activity involves interplay between several ionic currents that
influence spontaneous diastolic depolarisation of the sinoatrial node
- these
currents include the If current - the 'f' denotes 'funny' - called this because
it had unusual properties compared with other current systems known at the time
of its discovery
- If current is carried by both sodium and potassium ions
across the sarcolemma
- the If current is inward at voltages in the diastolic
range
- activated on hyperpolarisation (within the diastolic range of voltages regularly observed in cardiac pacemaker tissue)
- characterised by unusually low single-channel conductance and slow activation kinetics
- directly activated by intracellular cyclic adenosine monophosphate (cAMP) - the If is not linked to cAMP-dependent phosphorylation activity and is carried by the hyperpolarisation-activated cyclic nucleotide-gated family of ion channel
- the If current is inward at voltages in the diastolic
range
- If current is carried by both sodium and potassium ions
across the sarcolemma
- these
currents include the If current - the 'f' denotes 'funny' - called this because
it had unusual properties compared with other current systems known at the time
of its discovery