3. Cardiac Muscle Structure & Function Flashcards by Lindsey Herrera

When does state 4 end?

hydrolysis of ATP

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A faster ATPase would allow what change in the heartbeat?

make it faster

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What are the major regulatory proteins in the cross bridge?

the troponins

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

troponin-I

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Coupling between cardiac cells is both ____ and ___.

mechanical, electrical

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What is a myofiber?

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

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How is Ca++ removed from the cell?

active pumping

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What causes diastolic heart failure?

usually titin mutations or dysfunction

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What regulates Ca++ sensitivity?

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

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

titan

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

troponin-T

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

myofibrils

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What is titin?

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

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What is the A band?

thick filaments

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What is the active state?

the force-generating state during contraction

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

stroke volume

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

force; relaxation

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What is myosin composed of?

2 heavy chains and 4 light chains

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What is the Z line?

the overlap of thick filaments

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

slower

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

1; 2

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What is the Frank-Starling Law of the Heart?

increasing preload volume increases the force of contraction

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

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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What is aortic pressure?

afterload on the left side of the heart

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What is the overlap of thick filaments called

the Z line

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

Desmosomes

What is the only alpha-isoform in the heart?

tropomyosin

What is the transition state?

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

What are the thick filaments collectively called?

the A band

What is the H zone?

only actin, no thick filaments

What is troponin-T?

binds tropomyosin; developmental regulation of isoform expression

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

a sarcomere

What is afterload?

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

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

the afterload

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

stretch; contract

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

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

What is the I band?

thin filaments

What are the thin filaments collectively called?

the I band

What is a myofibril?

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

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

adhesion; passed to the other

What does troponin-C bind?

Ca++

What is tropomyosin?

the only alpha-isoform in the heart

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

Intercalated discs

What is a thin filament?

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

Where is tropomyosin found?

on actin in the myosin binding groove

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

the thin filament

What is preload?

the volume in the ventricle before ejection

What is the volume in the ventricle before ejection called?

preload

The _____ seem to regulate force whereas ____ regulate relaxation.

thin filament proteins; thin filament proteins

Humans have mostly what kind of myosin heavy chain?

beta

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

a myofiber

Name the 5 steps in the Contraction-relaxation cycle.

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

Where is actin found?

in the thin filament

What is a thick filament?

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

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

actin

Where does the increase of Ca++ come from?

the sarcoplasmic reticulum and thru plasma channels

What do gap junctions provide?

low resistance pathways for electrical current

Cardiac muscle cells are connected to each other via \_\_\_\_.

intercalated discs

What is state 1?

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

What is pulmonary hypertension?

increased afterload on the R side of the heart

What is a sarcomere?

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

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

desmosomes; gap junctions

What is troponin-I?

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

What kind of enzyme is myosin?

an ATPase

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

thick filaments

What kinds of cells are found in the heart?

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

\_\_\_\_\_ is regulated by stroke volume x heart rate.

Cardiac output (CO)

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

heart rate

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

Z discs