E-C Coupling HeartLab (Bioelectricity) Flashcards
what is Ohms law
Current (I) = Voltage (V)/Resistance(R)
what is the resistance in a cell with no ion channels
infinite resistance - no current
what is the resistance in a cell with closed ion channels
infinite resistance - no current
what is the resistance in a cell with all open ion channels
low resistance - high current
what does the Nernst equation calculate
the membrane potential at which the forces drive ion movements is at equilibrium, resulting in no net movement of ions
The resting membrane potential in the heart is determined by what ion’s movement
K+
At -89mV there will be no what
no movement of K+ ions
which K+ channel is mostly responsible for maintaining the resting membrane potential in non-nodal cardiomyocytes
IK1 current (mediated by Kir2.1)
The IK1 current (mediated by Kir2.1) is the K+ channel mostly responsible for maintaining the resting membrane potential in what
non-nodal cardiomyocytes
The IK1 current (mediated by Kir2.1) is the K+ channel mostly responsible for maintaining what in non-nodal cardiomyocytes
resting membrane potential
what is a membrane potential
the electrical driving force dor ionic fluxes
The Na+/K+ ATPase maintains the hradient of what ions
Na+ and K+
Na+/K+ ATPase
P type ATPase
what is the functional subunit
alphabeta subunit
Na+/K+ ATPase
P type ATPase
how many TM domains does the alpha subunit have
10
Na+/K+ ATPase
P type ATPase
alpha subunit is the binding site for what
Na +, K+ ATP
Na+/K+ ATPase
P type ATPase
How many TM domains does the beta subunit have
1
Na+/K+ ATPase
P type ATPase
What is the role of the beta subunit
trafficking of the complex to sarcolemma
Na+/K+ ATPase
P type ATPase
“y subunit”
acts as a what for the Na/K+/ATPase
on/off switch
phosphorylated - unbound-on
de-phosphorylated-bound-off
The RMP of a cradiomyocyte is very what (charge)
negative
As the Na+/K+ ATPase pumps K in and NA out, describe the concentration difference
High NA+ outside, low inside
Low K+ outside, high inside
the membrane permeability for K+ is much higher than Na+ because»»>
Na+ channels are mainly closed at rest
K+ selective channels allow leakage of what along its conc gradient
K+
What equation can be used to preict the fate of the membrane potential when a particular ion channel opens
Nernst equation
how many phases does the cardiac AP have
5
0,1,2,3,4
Opening of a what channel leads to depolarisation
Na+ selective channel
Voltage-activated Na channels can be found where
excitable tissue
Voltage-activated Na channels are responsible for what
fast upstroke of action potential
how many homologous domains does the voltage-activated sodium channel have
4
how many transmembrane segments foes the voltage activated sodium channel have
6
in the voltage activated sodium channel, there are 6 TM segments in each, which TM domain contains the voltage sensor
4th
Activity of what Na channel underlies phase 0 of the cardiac AP
Nav1.5
ACtivity of Nav1.5 underlies phase _ of the cardiac AP
0
Early repolarisation (Phase 1) is mediated by what
transient outward K+ channels
Early Repolarisation (Phase_) is mediated by transient outward K+ channels
1
In phase 1, a second transient outward current is carried by a what
a Ca2+ activated Cl- current
Phase 2 of the cardiac AP is known as what
the plateau period
why is Phase 2 known as the plateau period
mixture of inward and outward currents
The plateau (Phase 2)
Inward current is composed of what Ca channel
L type
The plateau (Phase 2)
CA2+ entry provides the trigger for _________ during Excitation-contraction coupling
Ca2+ induced Ca2+ release
The plateau (Phase 2)
Ca2+ entry provides the trigger for Ca2+ induced Ca2+ release during what
Excitation-Contraction coupling
The plateau (Phase 2) (inward current)
Ca2+ entry provides the trigger for Ca2+ induced release during E_C coupling
what is the name for this
Ca2+ dependant inactivation
Negative feedback control
The plateau (Phase 2)
Outward current
due to what channels
rapid and slow-voltage gated K+ channels
what occurs in phase 3 of the cardiac AP
Late Repolarisation
what occurs during phase 4
Stabilisation of the reseing membrane potential
In phase 4 the stabilisation of the reseing membrane potential is due to closure of what ion channel and activation of what ion channel
closure: IcaL
Activation: Ik1
THE REFRACTORY PERIOD
what is the absolute refractory period
the period during an AP when no further excitation can occur
why does the refractory period exist
Recall that Nav1.5 undergoes activity dependant inactivation; the membrane first needs to repolarise (to the RMP) for Nav1.5 to enter the closed state before it can be reactivated
