GMS6530: ANTIARRHYTHMICS EXAM QUESTIONS AND
ANSWERS WITH COMPLETE SOLUTIONS VERIFIED
resting membrane potential
-90mV
-separation of charges across a cell membrane
-the concentration of ions inside and outside the cell
T/F: sodium is LOW inside the cell but HIGH outside the cell
True
T/F: calcium is LOW inside the cell but HIGH outside the cell
True
T/F: potassium is HIGH inside the cell but LOW outside the cell
True
Nernst potential
-the outward diffusive force on K+ ions balances the inward electrical force on the K+
ions
Nernst equation
-equilibrium between an ion concentration difference and the potential across a semi-
permeable membrane
-concerns concentrations inside and outside the cell
sarcolemmal ion channels
,-ligand gated (acetylcholine or K-ATP)
-voltage gated (Kr, na, Ca)
-specialized channels (connexins, mechanosensitive, temperature sensitive)
T/F: Na+ channel opening initiates the AP
True
Na+ channel opening
-upon reaching the threshold potential--> sodium channel proteins change conformation
to a conducting (open) state
-moves transmembrane potential towards ENa (+40mV)
-surge of Na ion movement lasts only 1 msec after which the channel protein changes
conformation from the open state to an inactivated, non-conducting state
sodium channel inactivation
1. sodium channels activate to open at -70mV
2. carry large inward current to depolarize the cell
3. inactivate quickly
4. while inactivated, Na+ channel cannot activate at or above its threshold potential
5. Na+ channels undergo fast inactivation by the IG (inactivation gate)
6. Na+ channels undergo slow inactivation during that involves a conformation change
resulting in occlusion of the Na+ channel pore
what maintains the plateau of the action potential?
-Ca2+ channel opening
-Na+/Ca2+ exchanger
what terminates the action potential?
, -Ca2+ channel closing
-opening of K+ channels
inward-rectifier K+ current
-maintains baseline potential
-present in myocytes
-ABSENT in SA node and AV nodes
-two transmembrane segments in each domain
T/F: when activated, the IK(Ach) channel functions like the inward-rectifier K+
channel
True
what activates the IK(ACh) channel?
-parasympathetic impulses
-acetylcholine activates channel during rapid repolarization and during diastole
parasympathetic activation of the IK(ACh) channel involves:
-ligand, ACh
-parasympathetic M2 receptor in the cell membrane
-a G protein that phosphorylates the channel
action potential heterogeneity
-shape differs in atria vs ventricles
-types and numbers of channels spread throughout vary across heart
fast response myocardial cells
-found in cells designed to contract and conduct
-based on membrane properties and ionic currents
ANSWERS WITH COMPLETE SOLUTIONS VERIFIED
resting membrane potential
-90mV
-separation of charges across a cell membrane
-the concentration of ions inside and outside the cell
T/F: sodium is LOW inside the cell but HIGH outside the cell
True
T/F: calcium is LOW inside the cell but HIGH outside the cell
True
T/F: potassium is HIGH inside the cell but LOW outside the cell
True
Nernst potential
-the outward diffusive force on K+ ions balances the inward electrical force on the K+
ions
Nernst equation
-equilibrium between an ion concentration difference and the potential across a semi-
permeable membrane
-concerns concentrations inside and outside the cell
sarcolemmal ion channels
,-ligand gated (acetylcholine or K-ATP)
-voltage gated (Kr, na, Ca)
-specialized channels (connexins, mechanosensitive, temperature sensitive)
T/F: Na+ channel opening initiates the AP
True
Na+ channel opening
-upon reaching the threshold potential--> sodium channel proteins change conformation
to a conducting (open) state
-moves transmembrane potential towards ENa (+40mV)
-surge of Na ion movement lasts only 1 msec after which the channel protein changes
conformation from the open state to an inactivated, non-conducting state
sodium channel inactivation
1. sodium channels activate to open at -70mV
2. carry large inward current to depolarize the cell
3. inactivate quickly
4. while inactivated, Na+ channel cannot activate at or above its threshold potential
5. Na+ channels undergo fast inactivation by the IG (inactivation gate)
6. Na+ channels undergo slow inactivation during that involves a conformation change
resulting in occlusion of the Na+ channel pore
what maintains the plateau of the action potential?
-Ca2+ channel opening
-Na+/Ca2+ exchanger
what terminates the action potential?
, -Ca2+ channel closing
-opening of K+ channels
inward-rectifier K+ current
-maintains baseline potential
-present in myocytes
-ABSENT in SA node and AV nodes
-two transmembrane segments in each domain
T/F: when activated, the IK(Ach) channel functions like the inward-rectifier K+
channel
True
what activates the IK(ACh) channel?
-parasympathetic impulses
-acetylcholine activates channel during rapid repolarization and during diastole
parasympathetic activation of the IK(ACh) channel involves:
-ligand, ACh
-parasympathetic M2 receptor in the cell membrane
-a G protein that phosphorylates the channel
action potential heterogeneity
-shape differs in atria vs ventricles
-types and numbers of channels spread throughout vary across heart
fast response myocardial cells
-found in cells designed to contract and conduct
-based on membrane properties and ionic currents
