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Flashcards in cardiac muscle structures 2 Deck (30):
1

contraction and relaxation cycle

1. Action potential leads to calcium release.
2. Calcium binds to troponin C.
3. Troponin complex undergoes structural change, moving tropomyosin out of the way.
4. Myosin binds actin and crossbridge moves.
5. Calcium is released, tropomyosin reblocks binding site - relaxation

2

crossbridge is

myosin binding actin, which ultimately generates force

3

Cross bridges are initially in a

weakly bound, non-force-generating “rest” state (state 1) during diastole.

4

The triggering of force generation and contraction is governed by

Ca2+ fluxes determined by the dynamics of electrochemical coupling of Ca2+ release and Ca2+ binding to cTnC.

5

4 state cross bridge cycle model

1. rest state
2. transition state
3. active state
4. active state

6

rest state

1. no ca2+
2. weakly bound
3. non force generating

7

transition state

1. Ca2+ bound
2. XB weakly bound
3. non force generating

8

3. active state

1. calcium bound
2. XB strongly bound
3. force generating

9

4. active state

1. no calcium bound
2. XB strongly bound
3. force generating

10

Contractility describes the

relative ability of the heart to eject a stroke volume (SV) at a given pre- vailing afterload (arterial pressure) and preload (end-diastolic volume; EDV).

11

during contraction, what occurs

I band and H band decrease

A band does not change!!

12

titin forms

an elastic spring
one of the major proteins responsible for passive elastic properties of the cell (and thus for the diastolic properties of the heart)

13

titin isoforms

1. N2B
2. N2BA

14

CO =

SV x HR

15

stroke volume is

how much blood is pumped out with each beat

16

after load

pressure that ventricles are pushing against

Aortic (left side) or pulmonary pressure (right side)

17

preload

volume in ventricle before ejection

18

what special features allow heart to beat?

the organization of the muscle, they wrap around the heart in a very coordinated fashion

19

contraction starts in the

apex and squeezed coordinately in a spiral way up.

20

which are mechanical adhesions?

desmosomes

21

which are electrical adhesions?

gap junctions

22

thin filament contains

actin

23

thick filament contains

myosin

24

troponin I is typically located

on the actin and it covers the myosin binding site

25

contraction is

systole

26

relaxation is

diastole

27

where does regulation of the myofilament activation occur?

on the thin filament or thick filament

28

on the thin filament, regulation is

force, active contraction or sensitivity to calcium

TnC, TnT, TnI, Tm

29

on the thick filament, regulation is

relaxation kinetics, diastole, passive tension

MLC1, MLC2 or MyBP-C

30

in sliding filament, the length of actin or myosin

do not change
but titin does become more or less coiled