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Physiology and Pharmacology > E-C Coupling and Cross Bridge Linking > Flashcards

E-C Coupling and Cross Bridge Linking Flashcards

1
Q

Why are Myofibrils multinucleate?

A

As they form from the fusion of myoblasts during development

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2
Q

What protein is found in thick filaments?

A

Myosin

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3
Q

What proteins are found in thin filaments?

A

Actin, tropomyosin and troponin.

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4
Q

Are A bands light or dark bands?

A

Dark bands

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5
Q

Are I bands light or dark bands?

A

Light bands

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6
Q

What are A bands comprised of?

A

Thick filaments with thin filaments that overlap it on either end

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7
Q

What is he H zone?

A

The area on the A band that is solely thick filaments as the thin don’t reach.

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8
Q

What is the M line?

A

A series of proteins that that hold units together

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9
Q

What is the I band comprised of?

A

Thin filaments from the end of the A band

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10
Q

Where to two Sarcomeres bind?

A

At the Z line

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11
Q

How does muscle growth occur?

A

By the addition of Sarcomeres

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12
Q

How many thin filaments surround each thick filament?

A

Six

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13
Q

How many thick filaments surround each thin filament?

A

Three

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14
Q

What gives the appearance of striation?

A

Aligned A bands

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15
Q

What is the main structural component of think filament?

A

A double traded helix of f actin

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16
Q

What is the structure of troponin?

A

It has 3 spherical components: troponin c, troponin I and troponin T

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17
Q

What is the function of troponin T?

A

It binds a single molecule of tropomyosin

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18
Q

What is the function of troponin I?

A

It binds to actin and inhibits contraction

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19
Q

What is the function of troponin C?

A

It binds calcium ions.

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20
Q

What is the structure of myosin?

A

It is comprised of two subunits with intertwining tails and globular heads which contain an actin binding site and an ATP-are site.

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21
Q

How do the fibres of myosin run?

A

Half in one direction, half in the other

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22
Q

What is each myosin II molecule comprised of?

A

A double trimmer of 2 heavy chains, 2 regulatory chains and 2 alkali chains

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23
Q

What happens at the hinge of the myosin molecule?

A

It opens to form heads

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24
Q

How does the regulatory chain of myosin regulate ATPase activity?

A

Via phosphorylation by kinases

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25
Q

What is the energy source for cross-bridge linking?

A

Hydrolysed ATP

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26
Q

What is the means of muscle contraction?

A

Sliding filament action

27
Q

Which filaments move during sliding filament action?

A

Thin filaments

28
Q

Is A band width affected by sliding filament action?

A

No

29
Q

How is I band width affected by sliding filament action?

A

It decreases

30
Q

How is H zone width affected by sliding filament action?

A

It decreases

31
Q

What happens to the distance between z lines during sliding filament action?

A

It decreases

32
Q

What is the action of all six thin filaments around a thick filament in sliding filament action?

A

They are simultaneously pulled inward

33
Q

What is rigor mortis?

A

Sarcomeres stuck in contraction as ATP cannot be produced post mortem and so they are stuck in cross bridge linking

34
Q

What determines the duration of muscle contraction?

A

The duration of time in which cytosolic Ca levels are elevated

35
Q

What are t-tubules?

A

Invaginations in the sarcolemma

36
Q

Where do t-tubules penetrate the muscle?

A

At A-I band junctions

37
Q

Of what is a triad comprised?

A

A t-tubule and 2 cisrternae

38
Q

To what does depolarisation of the t-tubule membrane lead?

A

Calcium ion release from the triad

39
Q

What is required to terminate contraction?

A

Reuptake of Ca into sarcoplasmic reticulum

40
Q

What activates troponin C and so causes cross bridge cycling?

A

Increase in intracellular Ca concentration

41
Q

How may cells get rid of excess Ca to terminate contraction?

A

By extrusion through NCX exchanger or by intake into the SR by PMCA pump

42
Q

What mediates Ca uptake?

A

SR Ca pump

43
Q

What inhibits the Sr Ca pump?

A

High Ca concentration in SR

44
Q

What is the principle Ca binding protein in the SR?

A

Calsequestrin

45
Q

what is Calreticulum?

A

A Ca binding protein found in high concentrations in the SR of smooth muscle

46
Q

How many Ca can each protein in the SR bind?

A

Up to 50

47
Q

What is the function of the SERCA pump?

A

Restores Ca concentration to resting concentration

48
Q

When does contraction occur?

A

During the excitatory pulse of calcium

49
Q

What must occur for a contraction to continue?

A

A series of action potentials followed by a series of Ca excitatory pulses

50
Q

What is the sliding action?

A

The time required to bring about tensions for contraction

51
Q

What is the latent period?

A

The time delay between stimulation and contraction

52
Q

What is the contraction time?

A

The time from contraction onset to peak tension

53
Q

When does the contractile response end?

A

When the lateral sacs have taken up all the Ca released by the action potential

54
Q

What is the relaxation time?

A

The time from peak tension to full relaxation

55
Q

When does the EPP and the AP stop?

A

When AChE removes ACh from the NMJ

56
Q

What triggers Ca pumps to return Ca into the SR?

A

The local AP no longer being in the t-tubules

57
Q

What triggers the troponin-tropomyosin complex to return to its blocking position that block a cross-bridge link?

A

Removal of cytoplasmic Ca into the SR

58
Q

What is the final step in relaxation?

A

Thin filaments returning to their resting position

59
Q

What is RYR?

A

A Ca channel on the membrane of the SR

60
Q

What changes the conformation of RYR and opens it?

A

Physical attachment of DHP in response to the AP

61
Q

What happens to allow myosin binding sites on actin to become free?

A

A conformational change in tropomyosin

62
Q

What ill happen if Ca is still present father a power stroke has occurred?

A

Another power stroke will arise

63
Q

What allows myosin to detach from actin?

A

ATP binding

Physiology and Pharmacology (7 decks)

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