E-C Coupling HeartLab (Bioelectricity)

Question 1

what is Ohms law

Answer 1

Current (I) = Voltage (V)/Resistance(R)

Question 2

what is the resistance in a cell with no ion channels

Answer 2

infinite resistance - no current

Question 3

what is the resistance in a cell with closed ion channels

Answer 3

infinite resistance - no current

Question 4

what is the resistance in a cell with all open ion channels

Answer 4

low resistance - high current

Question 5

what does the Nernst equation calculate

Answer 5

the membrane potential at which the forces drive ion movements is at equilibrium, resulting in no net movement of ions

Question 6

The resting membrane potential in the heart is determined by what ion’s movement

Answer 6

K+

Question 7

At -89mV there will be no what

Answer 7

no movement of K+ ions

Question 8

which K+ channel is mostly responsible for maintaining the resting membrane potential in non-nodal cardiomyocytes

Answer 8

IK1 current (mediated by Kir2.1)

Question 9

The IK1 current (mediated by Kir2.1) is the K+ channel mostly responsible for maintaining the resting membrane potential in what

Answer 9

non-nodal cardiomyocytes

Question 10

The IK1 current (mediated by Kir2.1) is the K+ channel mostly responsible for maintaining what in non-nodal cardiomyocytes

Answer 10

resting membrane potential

Question 11

what is a membrane potential

Answer 11

the electrical driving force dor ionic fluxes

Question 12

The Na+/K+ ATPase maintains the hradient of what ions

Answer 12

Na+ and K+

Question 13

Na+/K+ ATPase
P type ATPase
what is the functional subunit

Answer 13

alphabeta subunit

Question 14

Na+/K+ ATPase
P type ATPase
how many TM domains does the alpha subunit have

Answer 14

10

Question 15

Na+/K+ ATPase
P type ATPase
alpha subunit is the binding site for what

Answer 15

Na +, K+ ATP

Question 16

Na+/K+ ATPase
P type ATPase
How many TM domains does the beta subunit have

Answer 16

1

Question 17

Na+/K+ ATPase
P type ATPase
What is the role of the beta subunit

Answer 17

trafficking of the complex to sarcolemma

Question 18

Na+/K+ ATPase
P type ATPase
“y subunit”
acts as a what for the Na/K+/ATPase

Answer 18

on/off switch
phosphorylated - unbound-on
de-phosphorylated-bound-off

Question 19

The RMP of a cradiomyocyte is very what (charge)

Answer 19

negative

Question 20

As the Na+/K+ ATPase pumps K in and NA out, describe the concentration difference

Answer 20

High NA+ outside, low inside
Low K+ outside, high inside

Question 21

the membrane permeability for K+ is much higher than Na+ because»»>

Answer 21

Na+ channels are mainly closed at rest

Question 22

K+ selective channels allow leakage of what along its conc gradient

Answer 22

K+

Question 23

What equation can be used to preict the fate of the membrane potential when a particular ion channel opens

Answer 23

Nernst equation

Question 24

how many phases does the cardiac AP have

Answer 24

5

0,1,2,3,4

Question 25

Opening of a what channel leads to depolarisation

Answer 25

Na+ selective channel

Question 26

Voltage-activated Na channels can be found where

Answer 26

excitable tissue

Question 27

Voltage-activated Na channels are responsible for what

Answer 27

fast upstroke of action potential

Question 28

how many homologous domains does the voltage-activated sodium channel have

Answer 28

4

Question 29

how many transmembrane segments foes the voltage activated sodium channel have

Answer 29

6

Question 30

in the voltage activated sodium channel, there are 6 TM segments in each, which TM domain contains the voltage sensor

Answer 30

4th

Question 31

Activity of what Na channel underlies phase 0 of the cardiac AP

Answer 31

Nav1.5

Question 32

ACtivity of Nav1.5 underlies phase _ of the cardiac AP

Answer 32

0

Question 33

Early repolarisation (Phase 1) is mediated by what

Answer 33

transient outward K+ channels

Question 34

Early Repolarisation (Phase_) is mediated by transient outward K+ channels

Answer 34

1

Question 35

In phase 1, a second transient outward current is carried by a what

Answer 35

a Ca2+ activated Cl- current

Question 36

Phase 2 of the cardiac AP is known as what

Answer 36

the plateau period

Question 37

why is Phase 2 known as the plateau period

Answer 37

mixture of inward and outward currents

Question 38

The plateau (Phase 2) Inward current is composed of what Ca channel

Answer 38

L type

Question 39

The plateau (Phase 2) CA2+ entry provides the trigger for _________ during Excitation-contraction coupling

Answer 39

Ca2+ induced Ca2+ release

Question 40

The plateau (Phase 2) Ca2+ entry provides the trigger for Ca2+ induced Ca2+ release during what

Answer 40

Excitation-Contraction coupling

Question 41

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

Answer 41

Ca2+ dependant inactivation Negative feedback control

Question 42

The plateau (Phase 2) Outward current due to what channels

Answer 42

rapid and slow-voltage gated K+ channels

Question 43

what occurs in phase 3 of the cardiac AP

Answer 43

Late Repolarisation

Question 44

what occurs during phase 4

Answer 44

Stabilisation of the reseing membrane potential

Question 45

In phase 4 the stabilisation of the reseing membrane potential is due to closure of what ion channel and activation of what ion channel

Answer 45

closure: IcaL Activation: Ik1

Question 46

THE REFRACTORY PERIOD what is the absolute refractory period

Answer 46

the period during an AP when no further excitation can occur

Question 47

why does the refractory period exist

Answer 47

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