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zz CVPR > C-Cardiac MuscleMyocyte Structure & Function > Flashcards

C-Cardiac MuscleMyocyte Structure & Function Flashcards

1
Q

Regulators of Cardiac Output

A

preload
afterload
contractility

CO= Heart Rate x Stroke Volume

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2
Q

Afterload is

A

pressure ventricles are pushing against to eject blood from the heart

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3
Q

Preload is

A

volume in the heart (ventricle) before it beats

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4
Q

Heart is made up of approximately 2 -3 billion _________ but this accounts for only about 1/3 of the number of cells

A

cardiac muscle cells

responsible for corrdinated contraction

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5
Q

Other cell types include fibroblasts, endothelial cells, smooth muscle cells, and immune cells in the

A

heart

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6
Q

Contraction starts at

A

the apex ofthe heart

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7
Q

Other cell types include ___________ in the heart

A

fibroblasts
endothelial cells
smooth muscle cells
immune cells

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8
Q

Fibrillar collagen type I and III are the most predominant components of the ECM and disruptions in the ECM occur with disease and___________

A

cardiac remodeling

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9
Q

Cardiac muscles are __________ (like skeletal muscle)

A

striated

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10
Q

Cardiac muscles are ___________ direct neural control (unlike skeletal)

A

NOT under

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11
Q

Cardiac muscle cells are shorter, narrower & richer in mitochondria than skeletal muscle cells have __________ nucleus

A

only one or two

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12
Q

__________ activity of myosin is slower in cardiac than skeletal but faster than smooth muscle

A

ATPase

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13
Q

Cardiac muscle cells are connected with each other through_________-

A

intercalated discs

Coincide with the Z discs; contain desmosomes and gap junctions

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14
Q

Ca2+ binding to troponin regulates __________ interaction

A

actomyosin

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15
Q

coupling between cardiac muscle cells is both___________

A

mechanical and electrical

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16
Q

Desmosomes provide adhesion and assure that the ______ generated in one cell passes to the other (connects to ECM)

A

force

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17
Q

Ca2+ binding to ________ regulates actomyosin interaction

A

troponin

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18
Q

_________ provide low resistance pathways for electrical current

A

Gap junctions

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19
Q

_______ binding to troponin regulates actomyosin interaction

A

Ca2+

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20
Q

Composed of hundreds of long, contractile myosin molecules arranged in a staggered side by side complex

A

Thick Filament

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21
Q

Composed of hundreds of long, contractile myosin molecules arranged in a staggered side by side complex

A

Thin Filament

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22
Q

The unit of contractile activity composed mainly of actin and myosin and extending from Z line to Z line in a myofibril

A

Sarcomere

23
Q

End-to-end arrays of identical sarcomeres

A

Myofibril

24
Q

A single multinucleate muscle cell containing all the usual cell organelles plus many myofibrils

A

Myofiber

25
Q

Composed of two heavy chains and four light chains, ATPase activity (a vs b)

motor proteins that move along actin filaments, while hydrolyzing ATP.

A

Myosin

26
Q

Similar to skeletal muscle myosin

Binds tropomyosin and troponin

A

Actin

27
Q

A dumbbell shaped protein with the N-lobe containing only ONE Ca2+-binding site (unlike skeletal which contains two)

A

Troponin C (TN-C)

28
Q

Contains a unique N-terminal extension of 32 amino acids that contains 2 PKA phosphorylation sites critical for adrenergic responsiveness of the heart.

A

Troponin I (TN-I)*****

-extension interacts with TN-C but is released with phosphorylation.

29
Q

Binds tropomyosin. Developmental regulation of isoform expression (and perhaps pathological regulation).

A

Troponin T (TN-T)

30
Q

Only alpha isoform in the heart (but may be pathologically regulated)

A

Tropomyosin

31
Q

Troponin i

A

lies over myosin binding site
inhibitor

phosphorylation sites critical for adrenergic responsiveness of the heart.

interacts with TN-C but is released with phosphorylation.

32
Q

AP leads to Ca release.
Ca binds to troponin C.
Troponin complex undergoes structural change, moving tropomyosin out of the way.
Myosin binds actin and crossbridge moves.
Ca is released, tropomyosin reblocks binding site - relaxation
**

A

Contraction – Relaxation Cycle

33
Q

Contraction – Relaxation Cycle**

A

AP leads to Ca release.

Ca binds to troponin C.

Troponin complex undergoes structural change, moving tropomyosin out of the way.

Myosin binds actin and crossbridge moves.

Ca is released, tropomyosin reblocks binding site - relaxation

34
Q

Cross bridge

A

myosin head attached/binding to actin

ultimately generates force

35
Q

“rest” state (state 1) during diastole

A

Cross bridges are initially in a weakly bound, non-force-generating “rest” state

36
Q

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 ________

A

cTnC.

Cross bridges and thin filaments now enter into a transition state (state 2)

37
Q

CO =

A

heart rate x stroke volume.

38
Q

actin (thin) filaments of muscle fibres slide past the myosin (thick) filaments during muscle contraction, while at constant length.

A

Sliding Filament Hypothesis

39
Q

Titin forms an ________, and there are many points of regulation within titin

A

elastic spring

major protein in cardiac muscle cell

40
Q

also known as connectin, is a flexible intrasarcomeric filamentous protein, which is largest proteins known today.

A

titin

41
Q

Action potential leads ______ in the heart .

A

to ca release

42
Q

Calcium binds to ________ in the heart.

A

troponin C

43
Q

Troponin complex undergoes structural change, moving _______ out of the way.

A

tropomyosin

44
Q

Myosin binds _______ and crossbridge moves.

A

actin

45
Q

Calcium is released, __________ reblocks binding site - relaxation

A

tropomyosin

46
Q

The effect of increasing preload on force of contraction:

the greater the volume of blood entering the heart during diastole (end-diastolic volume), the greater the volume of blood ejected during systolic contraction (stroke volume) and vice versa.

A

Frank-Starling Law of the Heart

47
Q

Frank-Starling Law of the Heart

A

The Greater the Preload, the greater the force generated”

with a Length-tension relationship for the myocytes

48
Q

Mechanisms behind the length-tension relationship

A

Extent of overlap
Change in the sensitivity of the myofilament to calcium:
Increased calcium release

49
Q

At short lengths only a fraction of the potential cross-bridges are activated by a given increase in calcium.

At longer lengths, more of the cross-bridges become activated by the same change in intracellular calcium. No time delay in the “sensor”.

A

Change in the sensitivity of the myofilament to calcium

50
Q

Occurs several minutes after changing the length of the muscle. May be due to stretch-sensitive ion channels in the cell membrane.

A

Increased calcium release

51
Q

Calcium Sensitivity of Cardiac Muscle

Several factors regulate calcium sensitivity of the myofilament

A

Several factors regulate calcium sensitivity of the myofilament
TnI phosphorylation
Isoform composition
sarcomere length

52
Q

The responsiveness of the myofilament to calcium is___________

A

“calcium sensitivity”

53
Q

_________ is the central factor in myocardial contraction

A

Calcium

zz CVPR (32 decks)

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