1. Cardiac Action Potentials Flashcards
What three structures in the heart have pacemaker capability?
SA node
AV node
Pukinje fibers
What is the resting membrane potential for a “normal” cardiac myocyte?
-95
What is the resting membrane potential of an SA nodal myocyte?
-65
Do ventricular myocytes or atrial myocytes have a shorter action potential?
Atrial myocytes
What do K+(d) channels do?
They are the voltage gated potassium channels which open in phase 3
How does acetylcholine slow the heart rate?
They affect the Kb channels and keep them open, slowing phase 0 in the SA node.
ALSO it slows down the funny Na channels elongating phase 4
What channels close / open in phase 3 of the SA node?
Calcium channels close and Kb channels open.
In what phase do K(a) channels open?
Phase 1
Which phase is typically related to conductance velocity?
Phase 0
What would a negative lusitropic effect cause?
Longer duration of the relaxation of cardiac muscles.
What is the effect of a positive dromotropic effect?
Increased speed of contuction
What nerve supplies parasympathetic innervation to the heart?
The Vagus nerve