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Muscle > Structure of Muscles > Flashcards

Structure of Muscles Flashcards

1
Q

What is the name of the usually fixed point where the muscle attached and is this proximal or distal?

A

The origin

It is proximal

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2
Q

What is the name of the usually moveable attachment of the muscle and is this proximal or distal?

A

Insertion

It is distal

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3
Q

What exists between the origin and the insertion of a muscle?

A

The muscle belly

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4
Q

Skeletal Muscle fibres are mononucleated. T/F?

A

False

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5
Q

What is the name for a bundle of muscle fibres bound together by collagenous supporting tissue?

A

Fassicles

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6
Q

What is the name of the connective tissue which surrounds individual muscle fibres?

A

The endomysium

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7
Q

What is the name of the connective tissue which surrounds each fascicle?

A

The perimyosium

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8
Q

What is the name of the connective tissue which surrounds the whole muscle mast?

A

Epimysium

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9
Q

What is the role of the perimysium?

A

To protect the fascicles from damage. It also contains blood vessels and nerves the nourish the muscle fibres

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10
Q

Muscles which have small fascicles and a large proportion of perimysium are most likely involved in what kind of movement?

A

Fine, highly controlled movement (e.g. Movement of the fingers)

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11
Q

What binds skeletal muscle directly to the skeleton?

A

Tendons

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12
Q

What binds skeletal muscle indirectly to the skeleton?

A

Aponeurosis

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13
Q

Where are the nuclei of muscle fibres?

A

At the periphery

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14
Q

What is the name of the plasma membrane of muscle cells?

A

Sarcolemma

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15
Q

What is the name of the organelle of a muscle fibre which is analogous to the endoplasmic reticulum of other cells?

A

The sarcoplasmic reticulum

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16
Q

Where is calcium stored in muscle fibres?

A

The terminal cisternae of the sarcoplasmic reticulum

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17
Q

Large amounts of glycogen and myoglobin exist in the sarcoplasm. What is their role in a muscle fibre?

A

Glycogen - provides energy during muscle contraction by conversion to glucose for respiration
Myoglobin - acts as an oxygen store

18
Q

Each muscle fibre is composed of bundles of…?

A

Myofibrils

19
Q

What are the two main components of the myofibril?

A

The thin filament (mostly actin)

The thick filament (mostly myosin)

20
Q

What is the structure of myosin?

A

Myosin has two large heavy chains and four small light polypeptide chains. They combine to form two globular heads (of both heavy and light chains) and a long tail of the two intertwined heavy chains. The two heads stick out to the sides to form cross-bridges

21
Q

What are the two binding sites of the myosin molecule for?

A

The ATP binding site is to bind ATP and can also act as an ATP-ase
The other binding site is to bind to the thin filament

22
Q

What is the role of tropomyosin?

A

It sits on the actin element of the thin filament and stops myosin from binding to it.

23
Q

What is to role of troponin?

A

Troponin holds tropomyosin in its blocking position on the actin element of the thin filament.

24
Q

What is the structure of tropomyosin?

A

It is a long rod-shaped molecule comprised of two intertwined polypeptides and is about seven actin monomers long

25
Q

What is the structure of troponin?

A

It is a small globular protein and has three subunits:
TnI - inhibitory
TnT - tropomyosin binding
TnC - calcium binding

26
Q

What is the structure of actin?

A

Actin is made up of monomers (G actin) which polymerise (forming F actin) and is made up of to intertwined helical strands

27
Q

What is the role of the protein nebulin?

A

It is sheath-like and covers actin to help anchor the filaments to the Z line

28
Q

What is the role of dystophin?

A

It is a structural protein which links actin to the sarcolemma, helping to transmit tension from the filaments to the tendon of the muscle. It helps reinforce the strength of the sarcolemma

29
Q

In a microscopic view of a muscle fibre what does the A band represent?

A

The A band is a dark wide bind showing the thick filaments which reside in the middle of the sarcomere

30
Q

What is the Z line of the sarcomere?

A

One end of each thin filament is anchored to a network of interconnected proteins known as the Z line. Thin filaments from to adjacent cells are anchored to the two sides of the Z line. The Z line marks the boundary of the sarcomere.

31
Q

What is the name of the structural protein which makes up the Z line?

A

Alpha actinin

32
Q

In a microscopic view of a muscle fibre what does the I band represent?

A

The I band lies between the ends of adjacent A bands and shows the thin filaments which do not overlap with the thick filaments

33
Q

What is the M line?

A

The M line is in the middle of the sarcomere and joins to two halves of the thick filament

34
Q

What protein is the M line composed of?

A

Myomesin

35
Q

What is the name of the elastic protein which extends from the Z line to the M line and is linked to the M line proteins and the thick filaments?

A

Tintin

36
Q

In a microscopic view of a muscle fibre what does the H band represent?

A

The H band is a narrow, light band in the centre of the A band which shows the space between opposing ends of the two sets of thin filaments.

37
Q

What structure lies directly between and is intimately related to adjacent segments of the sarcoplamsic reticulum?

A

Transverse(T)-tubules

38
Q

What structure exists in the area where the A and I bands meet?

A

T-tubules

39
Q

What does a motor unit consist of?

A

A somatic motor neuron with all of the muscle fibres that it innervates

40
Q

What does motor recruitment refer to?

A

The number of motor units activated during a contraction

41
Q

The overall muscle movement produced depends on the recruitment of…?

A

Different sized motor units
Different strengths of motor unit
Quantity of motor units

42
Q

All the muscle fibres of one motor unit are of the same fibre type. T/F?

A

True

Muscle (9 decks)

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