Inward rectifier Channels E 120-100 20 Vm(mv) 7
17 Inward Rectifier Channels -120 -100 -80 -60 -40 -20 0 20 40 60 Current Vm (mV) 0 Ek
Role for Inward Rectitie Expressed primarily in non nodal tissues Sets resting potential in atrial and ventricular muscle Contributes to the late phase of action potential repolarization in non nodal cells 18
18 Role for Inward Rectifier ➢ Expressed primarily in non nodal tissues ➢ Sets resting potential in atrial and ventricular muscle ➢ Contributes to the late phase of action potential repolarization in non nodal cells
+20 2 0 3 90 300 t(msec) 19
19 t (msec) -90 0 +20 0 300 0 1 2 3 4
Inactivating K channelS (ITo) Ultra-rapid K channels(lp Cardiac voltage. Rapid k channels (lk " Slow"K channels(ks gated /K/Channels All structurally similar to nerve K channels ITo is an inactivating K channel-rapid repolarization to the plateau Kur functions like nerve K channel- fights with Ca to maintain plateau Kr Iks structurally and functionally complex 20
20 Cardiac Voltagegated K Channels ➢ All structurally similar to nerve K+ channels ➢ ITO is an inactivating K+ channel- rapid repolarization to the plateau ➢ IKur functions like nerve K+ channel- fights with Ca to maintain plateau ➢ IKr, IKs structurally and functionally complex Inactivating K channels (ITO) “Rapid” K channels (IKr) “Slow” K channels (IKs) “Ultra-rapid” K channels (IKur)
Cardiac Ca2+ Channels L-type Structurally rather similar to Nat channels Some functional similarity to Nat channels depolarization opens Ca2+ channels Functionally different than Nat channels slower to open very slow, rather incomplete inactivation generates much less current flow
21 Cardiac Ca2+ Channels ➢ L-type ➢ Structurally rather similar to Na+ channels ➢ Some functional similarity to Na+ channels ➢ depolarization opens Ca2+ channels ➢ Functionally different than Na+ channels ➢ slower to open ➢ very slow, rather incomplete inactivation ➢ generates much less current flow