cardiac muscle structures 2

Question 1

contraction and relaxation cycle

Answer 1

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

Question 2

crossbridge is

Answer 2

myosin binding actin, which ultimately generates force

Question 3

Cross bridges are initially in a

Answer 3

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

Question 4

The triggering of force generation and contraction is governed by

Answer 4

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

Question 5

4 state cross bridge cycle model

Answer 5

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

Question 6

rest state

Answer 6

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

Question 7

transition state

Answer 7

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

Question 8

3. active state

Answer 8

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

Question 9

4. active state

Answer 9

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

Question 10

Contractility describes the

Answer 10

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).

Question 11

during contraction, what occurs

Answer 11

I band and H band decrease

A band does not change!!

Question 12

titin forms

Answer 12

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)

Question 13

titin isoforms

Answer 13

1. N2B

2. N2BA

Question 14

CO =

Answer 14

SV x HR

Question 15

stroke volume is

Answer 15

how much blood is pumped out with each beat

Question 16

after load

Answer 16

pressure that ventricles are pushing against

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

Question 17

preload

Answer 17

volume in ventricle before ejection

Question 18

what special features allow heart to beat?

Answer 18

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

Question 19

contraction starts in the

Answer 19

apex and squeezed coordinately in a spiral way up.

Question 20

which are mechanical adhesions?

Answer 20

desmosomes

Question 21

which are electrical adhesions?

Answer 21

gap junctions

Question 22

thin filament contains

Answer 22

actin

Question 23

thick filament contains

Answer 23

myosin

Question 24

troponin I is typically located

Answer 24

on the actin and it covers the myosin binding site

Question 25

contraction is

Answer 25

systole

Question 26

relaxation is

Answer 26

diastole

Question 27

where does regulation of the myofilament activation occur?

Answer 27

on the thin filament or thick filament

Question 28

on the thin filament, regulation is

Answer 28

force, active contraction or sensitivity to calcium

TnC, TnT, TnI, Tm

Question 29

on the thick filament, regulation is

Answer 29

relaxation kinetics, diastole, passive tension

MLC1, MLC2 or MyBP-C

Question 30

in sliding filament, the length of actin or myosin

Answer 30

do not change

but titin does become more or less coiled