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SPR2015 > Cardiac Muscle Structure > Flashcards

Cardiac Muscle Structure Flashcards

1
Q

Relationship between exercise intensity and CO

A

Positive

Incr exercise and need of skeletal muscle, incr CO

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2
Q

Define Preload

A

volume in the ventricle before ejection

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3
Q

Define afterload

A

pressure ventricles pushing against to eject blood (usu aortic pressure or pulm HTN)

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4
Q

Largest cell population in heart

A

1) endothelial cells

2) cardiac fibroblasts

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5
Q

function of cardiac fibroblast

A

lay down ECM of heart for myocytes to function

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6
Q

most predominant components of ECM

A

fibrillar collagen type 1 and 3

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7
Q

Unique features of skeletal muscle

A

1) striated
2) not under direct neural control (like skeletal)
3) muscle shorter, narrower, richer in mitochondria than skeletal
4) ATPase activity of myosin slower in cardiac
5) Ca2+ binding to troponin C regulates actomyosin

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8
Q

cardiac muscle cells connected with each other through ____

A

intercalated discs

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9
Q

each cardiac muscle is from __ to __ and contain ___ and ___

A

z disc to z disc

contain desmosomes and gap junctions

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10
Q

function of desmosomes

A

adhesion and assure force transferred from cell to cell

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11
Q

function of gap jucntion

A

low resistance path for electric current

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12
Q

coupling between cardiac muscle cells is both ___ and ___

A

mechanical and electrical

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13
Q

what is cardiac muscle made primarily of

A

myocytes in a collagen weave

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14
Q

what does each cardiac myocyte contain?

A

contains multiple rod strands called myofibrils

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15
Q

what are myofibrils composed of?

A

end to end array of sarcomere

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16
Q

what is a sarcomere

A

contractile unit made of actin and myosin from Z to Z

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17
Q

what is a myofiber

A

1 multinucelate muscle cell with all usual organelles + myofibrils

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18
Q

what is in thin filament?

A

actin

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19
Q

what is in thick filament

A

myosin

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20
Q

what is a thin filament also known as

A

I band extending from Z line

21
Q

what is a thick filament also known as

A

A band-

22
Q

what is myosin made of?

A

2 heavy chains + 4 light chains (2 regul + 2 essential)

23
Q

what are the two forms of myosin?

A

alpha

beta

24
Q

which myosin isoform has higher ATPase activity? and which form is associated with heart failure?

A

higher ATPase = alpha

heart failure = beta

25
Q

what does actin bind on to?

A

tropomyosin

troponin

26
Q

what is troponin C structure

A

1 Ca2+ binding site

skeletal muscle has 2

27
Q

What is troponin I

A

has N-terminal extension with 2 PKA phosphorylation site

interacts with Trop C but is released with phsophorylation

28
Q

what is troponin T

A

binds tropomyosin

29
Q

what is tropomyosin

A

only alpha isoform in heart

30
Q

Cross bridge cycle

A

1) Depol open plasma membrane Ca2+ channel
2) Ca2+ binds RyR2 on membrane of SR to induce more Ca2+ release
3) Ca2+ binds Trop C –> conformation change in tropomyosin to expose cross bridge sites on actin
4) ATP on myosin hydrolyzed to ADP + Pi
5) Actin interact with myosin –> crossbridge
6) muscle contract when ADP dissoc
7) Ca2+ released from troponin resets tropomyosin blocking actin
8) ATP rebinds myosin head –> reset

31
Q

1 Rest state

4 state crossbridge cycle

A

No Ca2+
weakly bound
no force generate

32
Q 
4 state crossbridge cycle
#2 transition state
A

Ca2+ bound
cross bridge weak bound
no force generate

33
Q 
4 state crossbridge cycle
#3 active state
A

Ca2+ bound
cross bridge strong bound
force generate

34
Q 
4 state crossbridge cycle
#4 active state
A

No Ca2+
cross bridge strong bound
force generate

35
Q

How is cross bridge cycling regulated?

A

Via calcium flow (level of calcium determine whether cross bridge forms)

36
Q

Sliding filament hypothesis

how does thin filament change?

A

NO CHANGE IN LENGTH BTWN CONTRACT AND RELAX STATE

37
Q

Sliding Filament hypothesis

how does thick filament change

A

NO CHANGE IN LENGTH LIKE THIN BUT DOES CHANGE ORIENTATION OF HEAD

38
Q

Function of Titin

A

allow interaction btwn myosin and actin to contract and relax without changing intracellular distance btwn actin/myosin

diastolic propertis

39
Q

what are 2 diff titin isoforms? which is longer and less stiff?

A 
N2b 
N2ba (longer and less stiff)
40
Q

which titin isoform is found in diastolic heart failure

A

incr N2b

41
Q

what is frank starling law of heart

A

1) MORE VOLUME OF BLOOD ENTER HEART IN DIASTOLE (EDV)

2) MORE VOLUME BLOOD EJECT DURING SYSTOLE (SV)

42
Q

what is frank starling law of heart based on?

A

length tension relationship

incr fiber length, incr force of contraction (tension)

43
Q

how does length tension relationship apply to heart?

A

incr preload

incr fiber length

incr force of contraction

44
Q

is there a limit on length tension relationship?

A

YES, OVERSTRETCH BEYOND OPTIMUM WILL DECREASE TENSION AND CONTRACTION

45
Q

what are the mechanisms behind length-tension relationship

A

1) extent of overlap
2) changes in sensitivity of myofilament to calcium
3) incr calcium release

46
Q

mechanisms behind length tension relationship

extent of overlap

A

Change resting length of muscle –> proportional change in individual sarcomere

Peak at 2.2-2.3 uM

47
Q

mechanisms behind length tension relationship

change in sensitivity of myofilament to calcium

what is main factor in myocardial contraction

A

1) calcium is main factor in myocardial contraction

48
Q

mechanisms behind length tension relationship

change in sensitivity of myofilament to calcium

what is aclacium sensitivity

A

responsiveness of myofilament to calcium

49
Q

mechanisms behind length tension relationship

change in sensitivity of myofilament to calcium

what are factors that regulate calcium sensitivity of myofilament

A

Troponin I phosphorylation

Isoform composition

sarcomere length

SPR2015 (23 decks)

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