GMS6530 Antiarrhythmics Exam Questions And
Accurate Answers 2024-2025
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 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. inactivated, Na+ channel cannot activate at or above its threshold potential
5. Na+ channels are subjected to fast inactivation by the IG (inactivation gate)
6. Na+ channels are subjected to slow inactivation during which there is a conformation
change leading to 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
-contractile and conductile cells
-phases 0-4
0: INa
1: close INa ; open Ito (potassium)
2: Ca2+ in and K+ Out
3: increased K+ and decreased Ca2+
4: approx = -90mV
slow response cardiac cells
-nodal cells (SA node and AV node)
-based on ionic current
-NO RESTING POTENTIAL (-60mV and decreasing)
4: Na in, transient Ca in, falling K out
0: sustained Ca in, K out
2: falling Ca in, K out
3: K out only
Accurate Answers 2024-2025
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 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. inactivated, Na+ channel cannot activate at or above its threshold potential
5. Na+ channels are subjected to fast inactivation by the IG (inactivation gate)
6. Na+ channels are subjected to slow inactivation during which there is a conformation
change leading to 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
-contractile and conductile cells
-phases 0-4
0: INa
1: close INa ; open Ito (potassium)
2: Ca2+ in and K+ Out
3: increased K+ and decreased Ca2+
4: approx = -90mV
slow response cardiac cells
-nodal cells (SA node and AV node)
-based on ionic current
-NO RESTING POTENTIAL (-60mV and decreasing)
4: Na in, transient Ca in, falling K out
0: sustained Ca in, K out
2: falling Ca in, K out
3: K out only
