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Heart and Circulation > E-C Coupling HeartLab (Bioelectricity) > Flashcards

E-C Coupling HeartLab (Bioelectricity) Flashcards

1
Q

what is Ohms law

A

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

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2
Q

what is the resistance in a cell with no ion channels

A

infinite resistance - no current

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3
Q

what is the resistance in a cell with closed ion channels

A

infinite resistance - no current

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4
Q

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

A

low resistance - high current

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5
Q

what does the Nernst equation calculate

A

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

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6
Q

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

A

K+

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7
Q

At -89mV there will be no what

A

no movement of K+ ions

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8
Q

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

A

IK1 current (mediated by Kir2.1)

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9
Q

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

A

non-nodal cardiomyocytes

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10
Q

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

A

resting membrane potential

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11
Q

what is a membrane potential

A

the electrical driving force dor ionic fluxes

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12
Q

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

A

Na+ and K+

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13
Q

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

A

alphabeta subunit

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14
Q

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

A

10

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15
Q

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

A

Na +, K+ ATP

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16
Q

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

A

1

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17
Q

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

A

trafficking of the complex to sarcolemma

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18
Q

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

A

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

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19
Q

The RMP of a cradiomyocyte is very what (charge)

A

negative

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20
Q

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

A

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

21
Q

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

A

Na+ channels are mainly closed at rest

22
Q

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

A

K+

23
Q

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

A

Nernst equation

24
Q

how many phases does the cardiac AP have

A

5

0,1,2,3,4

25
Q

Opening of a what channel leads to depolarisation

A

Na+ selective channel

26
Q

Voltage-activated Na channels can be found where

A

excitable tissue

27
Q

Voltage-activated Na channels are responsible for what

A

fast upstroke of action potential

28
Q

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

A

4

29
Q

how many transmembrane segments foes the voltage activated sodium channel have

A

6

30
Q

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

A

4th

31
Q

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

A

Nav1.5

32
Q

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

A

0

33
Q

Early repolarisation (Phase 1) is mediated by what

A

transient outward K+ channels

34
Q

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

A

1

35
Q

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

A

a Ca2+ activated Cl- current

36
Q

Phase 2 of the cardiac AP is known as what

A

the plateau period

37
Q

why is Phase 2 known as the plateau period

A

mixture of inward and outward currents

38
Q

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

A

L type

39
Q

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

A

Ca2+ induced Ca2+ release

40
Q

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

A

Excitation-Contraction coupling

41
Q

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

A

Ca2+ dependant inactivation
Negative feedback control

42
Q

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

A

rapid and slow-voltage gated K+ channels

43
Q

what occurs in phase 3 of the cardiac AP

A

Late Repolarisation

44
Q

what occurs during phase 4

A

Stabilisation of the reseing membrane potential

45
Q

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

A

closure: IcaL
Activation: Ik1

46
Q

THE REFRACTORY PERIOD
what is the absolute refractory period

A

the period during an AP when no further excitation can occur

47
Q

why does the refractory period exist

A

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

48
Q
A

Heart and Circulation (6 decks)

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