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Tissues of the Body > Muscle > Flashcards

Muscle Flashcards

1
Q

Define myasthenia

A

Weakness of the muscles

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2
Q

Define myoclonus

A

sudden spasm of the muscles

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3
Q

What is the sarcoplasmic reticulum?

A

The SER of the muscle cells

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4
Q

What morphology defines skeletal muscle?

A

long, parallel cylinders with multiple peripheral nuclei and striations

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5
Q

What morphology defines cardiac muscle?

A

short, branched cylinders with a single, central nucleus and striations

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6
Q

What morphology defines smooth muscle?

A

spindle-shaped cells with tapering ends to cells, single, central nucleus and no striations

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7
Q

How is skeletal muscle derived?

A

mesodermally derived: myogenic stem cells produce myoblasts, formation of primary myotube, nuclei are displaced to periphery by newly synthesised myofilaments

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8
Q

What are the 2 types of muscle fibre?

A

red and white

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9
Q

What are the features of red muscle fibres?

A

smaller diameter, rich vascularisation, rich myoglobin, numerous mitochondria, contractions are slower and weaker, fatigue slowly, rich in oxidative enzymes, fewer neuromuscular junctions

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10
Q

What are the features of white muscle fibres?

A

larger diameter, poor vascularisation, poor myoglobin, few mitochondria, faster and stronger contractions, quickly fatigues, rich in ATP-ase, more neuromuscular junctions

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11
Q

Where are red muscle fibres found?

A

limb muscles and postural muscles

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12
Q

Where are white muscle fibres found?

A

extraocular muscles and fingers

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13
Q

Where is the epimysium found?

A

Surrounding the outside of the muscles

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14
Q

Where is the endomyosium found?

A

Surrounding individual muscle fibres

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15
Q

Where is the perimysium found?

A

Surrounding the fascicles of the muscle

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16
Q

What occurs at myotendinous junctions?

A

Skeletal muscle fibres interdigitate with tendon collagen bundles.

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17
Q

What are extrinsic muscles?

A

Muscles that have insertions in bone or cartilage.

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18
Q

What are intrinsic muscles?

A

Muscles that are not attached to bone.

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19
Q

Of the muscle bands A and I, which is dark and which is light?

A 
A = dark
I = light
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20
Q

What is the smallest unit of muscle?

A

Myofibrils

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21
Q

What happens to the bands during the sliding filament model?

A

H and I bands get smaller whilst the A band stays the same size

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22
Q

Which protein makes up the thin filaments?

A

Actin

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23
Q

Which protein makes up the thick filaments?

A

Myosin

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24
Q

What are the features of actin?

A

bistranded helix, tropomyosin wraps around actin, troponin complexes attach to tropomyosin

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25
Q

What can we use as a diagnostic for MI?

A

Troponin: released from ischaemic cardiac muscle within 1 hour of the MI

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26
Q

What are the features of myosin?

A

thick, rod-like structure with 2 protruding heads

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27
Q

How does calcium cause actin and myosin to join?

A

calcium binds to TnC of troponin, conformational change moves tropomyosin, exposes actin binding sites, myosin heads can attach to actin

28
Q

What are the steps for contraction?

A

myosin cross bridges attach to actin, working stroke: myosin head pivots and pulls on the actin filament, sliding it towards the M line, ATP attaches to the myosin head and the cross bridge detaches, myosin head is cocked to start again

29
Q

Why does rigor mortis occur?

A

The lack of ATP perpetuates the binding of the myosin cross bridge.

30
Q

Where are the T tubules placed in skeletal muscle?

A

Where the A and I bands join

31
Q

What is the sequence of events before muscle contraction occurs?

A

The nerve impulse arrives at neuromuscular junction and releases Ach into cleft. depolarisation of sarcomere, voltage-gated Na+ channels open, Na+ enters cells, depolarisation spreads over sarcolemma into T tubules, conformational change, gated calcium channels are activated, calcium released into the sarcoplasm, calcium binds to troponin and contraction cycle initiated.

32
Q

How is calcium removed when the nerve impulse for contraction ends?

A

Calcium is removed via active transport into the sarcoplasmic reticulum.

33
Q

What happens to myofibrils in cardiac muscle?

A

The myofibrils tend to fuse so that the myofilaments form continuous masses.

34
Q

What are intercalated discs?

A

substitutes for Z lines where cells meet consisting of gap junctions and adherens-type junctions

35
Q

Where are the T tubules in cardiac muscle?

A

Lie on the Z line

36
Q

In which muscle do diads and triads occur?

A 
Diads = cardiac
Triads = skeletal
37
Q

What are the features of the Purkinje fibres?

A

large cells with abundant glycogen, extensive gap junctions and extremely fast conduction

38
Q

Where would you find smooth muscle?

A

contractile walls of passages or cavities: blood vessels, gut, respiratory tract, genitourinary system

39
Q

Modified smooth muscle cells can occur as which 2 cells?

A

myoepithelial cells and myofibroblast cells

40
Q

What are myoepithelial cells?

A

star shaped cells formed by dendritic processes that form a basketwork around the secretory units of some exocrine glands and contraction assists secretion

41
Q

What are myofibroblast cells?

A

occur at wounds and produce collagenous matrix, draw wound edges together on contraction

42
Q

Which nervous system innervates smooth muscle?

A

Autonomic NS

43
Q

How are the filaments arranged in smooth muscle?

A

arranged diagonally within the cell, spiral down a long axis and contract in a twisting way

44
Q

Can skeletal muscle repair itself?

A

The cells cannot divide but the tissue can regenerate by mitotic activity of satellite cells.

45
Q

Can cardiac muscle regenerate?

A

No

46
Q

Can smooth muscle regenerate?

A

Yes - the cells retain some of their mitotic activity and can form new smooth muscle cells.

47
Q

How can muscle be remodelled?

A

actin and myosin filaments can be replaced, number of muscle fibres cannot change, just their size, number of myofilaments can increase or decrease

48
Q

What happens in the muscle when amount of exercise increases?

A

SR swells, increase volume of mitochondria, increase Z band width, increase ATPase, increase number of contractile proteins

49
Q

How often should you do high resistance exercise if you want to increase muscle mass?

A

2-3 days a week

3 sets of 8-12 reps

50
Q

How does high resistance exercise change muscle?

A

stimulates contractile protein synthesis (more filaments) and increases muscle mass and strength (hypertrophy)

51
Q

How often should you do endurance exercise?

A

5 days a week

30-60 minutes

52
Q

How does endurance exercise change muscle?

A

increased endurance without hypertrophy, stimulates synthesis of mitochondrial proteins and vascular changes allow for greater oxygen utilisation

53
Q

What is disuse atrophy?

A

The loss of protein and reduced fibre diameter which results in the loss of power.

54
Q

What happens when muscles are denervated?

A

weakness, flaccidity and muscle atrophy

55
Q

What is myasthenia gravis?

A

autoimmune destruction of end-plate ACh receptors, loss of junctional folds and widening of synaptic clefts

56
Q

What are the symptoms of myasthenia gravis?

A

fatiguability, sudden falling, drooping eyelids, double vision

57
Q

What is the treatment for myasthenia gravis?

A

acetylcholinesterase inhibitors and immune suppressants

58
Q

What is plasmapheresis?

A

Removal of harmful antibodies from patient serum

59
Q

What is conotoxin used for?

A

Painkiller used for patients who no longer respond to morphine.

60
Q

What are muscular dystrophies?

A

genetic disorders, progressive muscle weakness and wasting and there are 6 types

61
Q

What causes Duchenne muscular dystrophy?

A

Deficiency of dystrophin

62
Q

What causes Becker type muscular dystrophy?

A

altered form (truncated) of dystrophy

63
Q

What happens in muscular dystrophies?

A

muscle fibres tear apart on contraction, creatine kinase liberated into serum, calcium enters cells causing cell death (necrosis). Pseudohypertrophy occurs before fat and connective tissue replace muscle fibres

64
Q

What are the 2 types of skeletal muscle disorders?

A

denervation and myopathies

65
Q

Define myalgia

A

Muscle pain

Tissues of the Body (12 decks)

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