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MD2002 Lucas > Sarcomere Structure > Flashcards

Sarcomere Structure Flashcards

1
Q

What are the 3 layers that separate Muscles and what is contained in each of them?

A

Endomysium - separates muscle fibres

Perimysium - lies between fascicles/fasciculi

Epimysium - dense sheath on surface of bundles of fascicles

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2
Q

What are the 3 components of muscles?

A

Muscle fibre (cell) -> Fascicle -> muscle

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3
Q

Where is force from muscles transmitted to?

A

The force is transmitted from muscles through tendons to the bone

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4
Q

What are the 3 components of a muscle fibre cell and their function?

A

Sarcolemma - true cell membrane that encloses the muscle fibre

Sarcoplasm - intracellular fluid that fills spaces between myofibrils

Myofibril - mainly composed of acting and myosin filaments

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5
Q

Where does the nuclei of a muscle fibre cell sit?

A

On the outside on top of the sarcolemma

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6
Q

What is the sarcomere?

A

The portion of myofibril that lies between two Z-disks

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7
Q

Draw and label the structure of a sarcomere?

A
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8
Q

How do you recognise the A band under a microscope?

A

Its quite dark

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9
Q

What band is split half by the ends of 2 different sarcomeres? And what colour is this band?

A

I band

Light

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10
Q

What is in the H-zone?

A

The very middle of the Sacromere

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11
Q

What disks define the end of the sarcomere?

A

the 2 Z-disks

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12
Q

What is a myofibril?

A

The name for the individual rod like strand of muscle tissue/cell which all bundle together to form a fasicle

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13
Q

What is the M line?

A

The M line runs down the middle of the sarcromere and in the middle of the A band

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14
Q

What is the purple partin the sarcromere?

A

Thin actin filament

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15
Q

What is the dark proportion of the myofibril?

A

Thick myosin filament

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16
Q

How does Myosin attach to Actin?

A

Via its cross bridges which have actin binding sites

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17
Q

What does the myosin tails made from?

A

two intertwined heavy chains

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18
Q

What are the 2 binding sites found on Myosin fillaments?

A

Actin binding sites and ATP binding sites

19
Q

What do cross bridges do?

A

Attach to Actin and move their chains

20
Q

What filaments are thick and what ones are thin?

A

Myosin filaments are thick

Actin filaments are thin

21
Q

Give 2 features of Actin?

A

Actin is a contractile protein

Each G actin has a binding site for myosin

22
Q

What 2 other molecules are found in actin filaments?

A

Tropomyosin and Troponin

23
Q

What is the function of Tropomyosin?

A

Tropomyosin is a regulatory protein which overlaps the binding sites on actin for myosin, so it inhibits interation with myosin when Tropomyosin is in its relaxed state

24
Q

What is the function of Troponin?

A

Troponin is a regulatory calcium binding protein which forms a complex with the other proteins of the thin filament (Actin. and Tropomyosin)

Troponin binds to calcium and once its bound it changes conformation to pull tropomyosin away from the myosin interaction sites which regulates skeletal muscle contraction because it moves tropomysin away allowing the myosin to bind to actin.

25
Q

What protein attaches to keep myosin and actin in place together?

A

Titin

26
Q

Where does Titin attach to?

A

The Z-line

27
Q

What is the function of Titin?

A

To provide elasticity and stabilise myosin

28
Q

What is the role of Nebulin?

A

Nebulin helps align actin

29
Q

What are the 4 stuctural proteins?

A

Titin

Z line protein (alpha-actinin)

M-line proteins (myomesin, M-protein)

Nebulin

30
Q

What are the 4 contractile proteins, which are involved in contraction and movement of filaments?

A

Actin

Myosin

Tropomyosin

Troponin complex

31
Q

What is responsible for giving skeletal and cardiac muscles their striated appearance?

A

The thick and thin arrangement in Myofibrils

32
Q

Draw the what a Myofibril looks like and 3 different cross sections of where thick, thin and mixed filaments would occur

A
33
Q

What would you expect to see in cross sections of the I band, H zone, M line and the outer edge of the A band?

A
34
Q

What kind of structures would you expect to see in an A-band?

A

Primarily myosin filaments in the region of overlap

35
Q

What kind of structures would you expect to see in an I-band?

A

Actin filaments bisected by Z-line

36
Q

What kind of structures would you expect to see in the H-zone?

A

Region of A-band which contains only myosin filaments

37
Q

What occurs when a muscle goes from being relaxed to contracted?

A

The myosin and actin filaments move closer together and overlap more

H zone and the I band both shorten

38
Q

What are T-tubules and their function?

A

T-tubules are invagination of the sarcolemma of skeletal and cardiac muscle

  • Action potential is propagated from the end plate along the surface of the muscle fibre (sarcolemma)
  • Action potential is propagated into the fibre down the T-tubule membrane
  • Depolarisation of the T-tubule membrane is ‘signalled’ to the membrane of the terminal cisternae
39
Q

Draw how the T-tubules, Sarcoplamic reticulum and terminal cisternae interact with myofibrils?

A
40
Q

What is the Sarcoplasmic reticulum and its function?

A

Its the same as the endoplasmic reticulum found in most cells (contains tubules for sorting and transporting things)

Calcium is stored and release from here following membrane excitation

41
Q

How do T-tubules and Sarcoplasmic reticulum interact?

A

They are connection with junctions made from 2 intergral proteins, one in the T-tubules membrane and one in the Sarcoplasmic reticulum

The T-tubule protein is a modified voltage-sensitive calcium channel called dihydropyridine receptor (DHP) which acts as a voltage sensor

The Sarcoplasmic reticulumprotein is called ryanodien receptor (RYR) which forms a calcium channel

42
Q

How does T-tubules transport the action potentials?

A

T-tubule brings action potentials into the interior of the muscle fibre

43
Q

Where is calcium stored in the muscle?

A

In the Sacroplasmic reticulum

MD2002 Lucas (111 decks)

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