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CVPR Exam I > 3. Cardiac Muscle Structure & Function > Flashcards

3. Cardiac Muscle Structure & Function Flashcards

1
Q

When does state 4 end?

A

hydrolysis of ATP

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2
Q

A faster ATPase would allow what change in the heartbeat?

A

make it faster

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2
Q

What are the major regulatory proteins in the cross bridge?

A

the troponins

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3
Q

What is the inhibitory filament- inhibits myosin binding to actin- has a special N-terminal sequence for beta-adrenergic responsiveness?

A

troponin-I

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4
Q

Coupling between cardiac cells is both ____ and ___.

A

mechanical, electrical

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4
Q

What is a myofiber?

A

a single, multinucleate muscle cell containing all the usual cell organelles plus many myofibrils (a small bundle of cells)

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4
Q

How is Ca++ removed from the cell?

A

active pumping

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4
Q

What causes diastolic heart failure?

A

usually titin mutations or dysfunction

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5
Q

What regulates Ca++ sensitivity?

A

Troponin-I phosphorylation**, isoform composition, and sarcomere length

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6
Q

The elastic properties of ____ allows sarcomeres to stretch and contract over large distances.

A

titan

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7
Q

What binds tropomyosin and may be involved in the developmental regulation of isoform expression?

A

troponin-T

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8
Q

What are end-to-end arrays of identical sarcomeres called?

A

myofibrils

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8
Q

What is titin?

A

one of the major proteins responsible for passive elastic properties of the cell (forms an elastic springs)

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9
Q

What is the A band?

A

thick filaments

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10
Q

What is the active state?

A

the force-generating state during contraction

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12
Q

Cardiac output (CO) is regulated by _____ times heart rate.

A

stroke volume

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12
Q

The thin filament proteins seem to regulate ____ whereas thin filament proteins regulate ____.

A

force; relaxation

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13
Q

What is myosin composed of?

A

2 heavy chains and 4 light chains

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14
Q

What is the Z line?

A

the overlap of thick filaments

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14
Q

Beta-myosin has a ____ ATPase than alpha-myosin.

A

slower

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14
Q

How many Ca++ binding sites to troponin-C does cardiac muscle have? How many does skeletal muscle have?

A

1; 2

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14
Q

What is the Frank-Starling Law of the Heart?

A

increasing preload volume increases the force of contraction

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16
Q

Name 5 specialized features of cardiac muscle cells that allow it’s contractility.

A
  1. they’re striated 2. not under direct neural control 3. they’re shorter, narrower, and richer in mitochondria 4. slower ATPase activity 5. Ca++/troponin regulates actomyosin
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17
Q

What is aortic pressure?

A

afterload on the left side of the heart

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18
Q

What is the overlap of thick filaments called

A

the Z line

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19
Q

_____ provide adhesion and assure that force generated by one cell is passed to the other.

A

Desmosomes

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20
Q

What is the only alpha-isoform in the heart?

A

tropomyosin

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21
Q

What is the transition state?

A

Ca++ enters the myocyte, binds to troponin-C, conformational change occurs and moves tropomyosin out of the way (non-force generating)

22
Q

What are the thick filaments collectively called?

A

the A band

23
Q

What is the H zone?

A

only actin, no thick filaments

23
Q

What is troponin-T?

A

binds tropomyosin; developmental regulation of isoform expression

25
Q

What is the unit of contractile activity composed of actin and myosin extending from Z line to Z line in a myofibril?

A

a sarcomere

27
Q

What is afterload?

A

the pressure that the ventricles are pushing against to eject the blood

27
Q

What is the pressure that the ventricles are pushing against to eject the blood called?

A

the afterload

27
Q

The elastic properties of titan allows sarcomeres to ____ and _____ over large distances.

A

stretch; contract

28
Q

What 3 things underly the Frank-Starling Law on a molecular level?

A

length-tension relationship: 1. extent of overlap 2. change in Ca++ sensitivity 3. changes in Ca++ release

30
Q

What is the I band?

A

thin filaments

32
Q

What are the thin filaments collectively called?

A

the I band

34
Q

What is a myofibril?

A

end-to-end arrays of identical sarcomeres (smallest contractile unit of the heart)

36
Q

Desmosomes provide _____ and assure that force generated by one cell is ____.

A

adhesion; passed to the other

37
Q

What does troponin-C bind?

A

Ca++

38
Q

What is tropomyosin?

A

the only alpha-isoform in the heart

40
Q

_____ coincide with Z discs; they contain desmosomes and gap junctions.

A

Intercalated discs

41
Q

What is a thin filament?

A

hundreds of long, contractile actin molecules arranged in a staggered, side-by-side complex

41
Q

Where is tropomyosin found?

A

on actin in the myosin binding groove

43
Q

What are hundreds of long, contractile actin molecules arranged in a staggered, side-by-side complex called?

A

the thin filament

44
Q

What is preload?

A

the volume in the ventricle before ejection

45
Q

What is the volume in the ventricle before ejection called?

A

preload

46
Q

The _____ seem to regulate force whereas ____ regulate relaxation.

A

thin filament proteins; thin filament proteins

47
Q

Humans have mostly what kind of myosin heavy chain?

A

beta

48
Q

What is a single, multinucleate muscle cell containing all the usual cell organelles plus many myofibrils?

A

a myofiber

49
Q

Name the 5 steps in the Contraction-relaxation cycle.

A
  1. AP leads to Ca++ release 2. Ca++ binds to troponin-C 3. Troponin complex undergoes conformational change, moving tropomyosin out of the way 4. Myosin binds actin and crossbridge moves 5. Ca++ is released, tropomyosin reblocks active site, and relaxation
51
Q

Where is actin found?

A

in the thin filament

52
Q

What is a thick filament?

A

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

53
Q

The contractile protein ____ is much more stable and has less of a role in disease.

A

actin

54
Q

Where does the increase of Ca++ come from?

A

the sarcoplasmic reticulum and thru plasma channels

56
Q

What do gap junctions provide?

A

low resistance pathways for electrical current

58
Q

Cardiac muscle cells are connected to each other via ____.

A

intercalated discs

59
Q

What is state 1?

A

the rest state; no Ca++; myosin head weakly bound (non-force generating)

60
Q

What is pulmonary hypertension?

A

increased afterload on the R side of the heart

61
Q

What is a sarcomere?

A

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

62
Q

Intercalated discs coincide with Z discs; they contain _____ and _____.

A

desmosomes; gap junctions

63
Q

What is troponin-I?

A

it’s the inhibitory filament- inhibits myosin binding to actin- has a special N-terminal sequence for beta-adrenergic responsiveness

64
Q

What kind of enzyme is myosin?

A

an ATPase

65
Q

What are hundreds of long, contractile myosin molecules arranged in a staggered, side-by-side complex called?

A

thick filaments

66
Q

What kinds of cells are found in the heart?

A
  1. myocytes 2. fibroblasts 3. endothelial cells 4. smooth muscle cells 5. immune cells
67
Q

_____ is regulated by stroke volume x heart rate.

A

Cardiac output (CO)

68
Q

Cardiac output (CO) is regulated by stroke volume x _____.

A

heart rate

69
Q

Intercalated discs coincide with _____ ; they contain desmosomes and gap junctions.

A

Z discs

CVPR Exam I (29 decks)

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