Cardiac EC Coupling & Calcium Handling I Flashcards Preview

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Flashcards in Cardiac EC Coupling & Calcium Handling I Deck (29):
1

When Calcium enters the cell from a t-tubule, it triggers

a larger release of Ca from the SR

2

Contraction of cardiac muscle, as of skeletal muscle, is elicited by an increase in the
myoplasmic ________

calcium concentration

3

AP releases Ca from _____

RyR

4

binding of calcium to troponin on the thin filaments enables the force-producing interaction between the thin filaments and the myosin heads of the ________

thick filaments.

5

Two of the important proteins are myosin, which forms the thick filament, and actin, which forms the ________

thin filament.

6

exchanges 3 Na for 1 Ca and can run either direction:
calcium efflux in exchange for sodium influx or calcium influx in exchange for sodium efflux.

The NCX sodium/calcium exchanger

7

binding of calcium to troponin on the thin filaments enables the force-producing interaction between the thin filaments and the _________ of the thick filaments.

myosin heads

8

________form a class of intracellular calcium channels in various forms of excitable animal tissue like muscles and neurons

Ryanodine receptors (RyRs)

main source of Ca for contraction

9

The NCX sodium/calcium exchanger exchanges...

3 Na for 1 Ca and can run either direction

ca efflux in exchange for na influx or
ca influx in exchange for na efflux.

10

Two of the important proteins are myosin, which forms the ____, and actin, which forms the thin filament.

thick filament

11

binding of calcium to troponin on the ________ enables the force-producing interaction between the thin filaments and the myosin heads of the thick filaments.

thin filaments

12

Cardiac Muscle
ECC requires entry of _____

external Ca2+

13

Skeletal Muscle
ECC __________ require entry of external Ca2+

does NOT

14

Ca2+ binds to troponin on thin filaments and activates contraction in _______

both Cardiac and Skeletal Muscle

15

Located on the plasma membrane side is a type of
voltage-gated Ca2+ channel, termed the dihydropyridine receptor or DHPR

used clinically as _______

antihypertensive agents

16

Ca2+ enters via DHPR (“L-type Ca2+ channel”) and activates _________ to cause a much larger
flux of Ca2+ from SR into myoplasm

RyR2

1- sequence of events during excitation, contraction and relaxation of cardiac muscle cells

17

Ca2+ activates contraction by binding to troponin on ________


thin filaments


2- sequence of events during excitation, contraction and relaxation of cardiac muscle cells

18

Ca2+ is removed from the myoplasm by:

(i) SERCA2 pump located in longitudinal SR

(ii) NCX Na+/Ca2+ exchanger in junctional domains of plasma membrane and t-tubules.

3- sequence of events during excitation, contraction and relaxation of cardiac muscle cells

19

SERCA2 pump located in longitudinal SR
(2 Ca2+ ions per cycle);
Ca2+ diffuses within SR to terminal cisternae, where it binds to ________

calsequestrin (low affinity, high capacity calcium buffer)

20

NCX Na+/Ca2+ exchanger in junctional domains of _______

plasma membrane and t-tubules.

21

PMCA pump in surface membrane (_____ per cycle).

1 Ca2+

22

SERCA2 dominates because _______ and requires less energy because voltage is close to zero

longitudinal SR surrounds each myofibril

23

NCX is next in importance and can be ______

arrhythmogenic

24

In steady-state, Ca2+ released from SR is recycled back into SR by ______, and surface extrusion balances L-type Ca2+ current

SERCA2

25

NCX exchanges _______
It can run either direction

3 Na for 1 Ca

26

Ca released from the SR in a resting cardiomyocyte would cause _______, resulting in depolarization.

Na influx via NCX

27

Depolarization via NCX as a consequence of abnormal diastolic SR Ca release has been suggested to be a trigger for ________ that give rise to arrhythmias.

delayed after depolarizations

28

Formerly, cardiac glycosides (e.g., digitalis) was a common treatment. These inhibit Na/K ATPase and thus to reduced __________

extrusion of Ca via NCX.

29

beta blockers, ARBs, diuretics and DHPS are used to reduce ________

peripheral vascular resistance.