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MSK > Muscles > Flashcards

Muscles Flashcards

1
Q

Functions of skeletal musckes

A

Produce movement of body parts
Support soft tissues
Maintain posture and body position
Communication
Maintain body temperature
Control of openings and passageways

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2
Q

Universal characteristics of muscles

A

Responsiveness (excitability)
Conductivity
Contractility
Extensibility
Elasticity

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3
Q

Responsiveness - excitability

A

Capable of response to chemical signals, stretch or other signals and responding with electrical changes across plasma membrane

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4
Q

Extensibility

A

Capable of being stretched

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5
Q

Contractility

A

Shortens when stimulated

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6
Q

Elasticity

A

Returns to its original length after being stretched

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7
Q

Average length of myofibre

A

5cm

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8
Q

Average diameter of myofibre

A

100um

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9
Q

Number of sarcomeres per myofibril

A

10000

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10
Q

T-tubules

A

Sarcolemma invaginations that help propagate action potentials

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11
Q

3 layers of connective tissue that surround myofibres

A

Endomysium
Perimysium
Epimysium

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12
Q

Nuclei of skeletal muscle

A

Multinucleated
Nuclei at periphery of cell

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13
Q

Parts of sarcomere

A

Z line
I band
A band
H zone
M line

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14
Q

H zone

A

Only myosin

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15
Q

H zone

A

Both myosin and actin

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16
Q

I band

A

Only actin

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17
Q

Motor units

A

The neuron and its associated muscle fibres that it innervates

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18
Q

Small motor units

A

More precise movements

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19
Q

Large motor units

A

Less precise movements

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20
Q

What anchors the actin filament to the Z disc

A

Alpha-actinin
CapZ

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21
Q

What maintains the certain length of the actin filament

A

Tropomodulin

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22
Q

Nebulin

A

Consists of 35alphaA actin binding motifs
Acts as a molecular ruker

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23
Q

Titin

A

Maintains myosin filament
Acts as a molecular spring

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24
Q

What protein maintains the myosin filament in its position in the sarcomere

A

Titin

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25
Q

Calcium removal/ muscle relaxation

A

SERCA on SR
Ca2+ ATPase on membrane
Na+/Ca2+ exchanger on membrane

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26
Q

Number of myosin heads in each myosin filament

A

300

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27
Q

Control of ACh levels

A

Acetylcholinesterase removes ACh and stops contraction
Lack of depolarisation from neuron
Botulism toxin prevents release
Ca2+ channel blockers

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28
Q

How does botulism toxin prevent ACh release

A

SNAP protein inhibited

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29
Q

Contraction of muscles filament

A

ATP binds to myosin head, causing dissociation of actin-myosin complex
ATP is hydrolysed causing myosin head to return to resting conformation
A cross-bridge forms and myosin head binds to a new position on actin
Pi is released- myosin head changes conformation, resulting in power stroke. Filaments slide past each other
ADP is released

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30
Q

Neuromuscular junction

A

Action potential propagates down neurone to neuromuscular junction
Depolarisation = Ca2+ influx signalling vesicle release
SNARE (on vesicle) binds to SNAP and synaptobrevin (on nerve wall) and ACh is released by exocytosis
ACh receptors present on sarcolemma
Influx of Na+ causes depolarisation which is propagated down t-tubules
Ca2+ enters the myocyte through L-type Ca2+ channels (dihydropyridine reticulum)
Calcium-induced calcium-release through ryanodine receptors on sarcoplasmic reticulum
Ca2+ binds to troponin C causing a conformational change and exposing the myosin binding site in actin

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31
Q

What does Ca2+ bind to on actin filament to expose myosin heads

A

Troponin C

32
Q

Which receptors are found in the sarcoplasmic reticulum

A

Ryanodine receptors

33
Q

Type of receptors on t-tubules

A

L-type Ca2+ channels - dihydropyridine receptors

34
Q

Parts of Troponin

A

C
T
I

35
Q

Troponin I

A

Inhibitory subunit

36
Q

Troponin T

A

Binds to tropomyosin

37
Q

Troponin C

A

Ca2+ binds

38
Q

Cell characteristics of skeletal muscles

A

Long
Cylindrical
Striated

39
Q

Tropomyosin

A

Covers myosin-binding sites on actin

40
Q

Skeletal muscle neurotransmitter

A

ACh

41
Q

Smooth muscle neurotransmitter

A

ACh
Noradrenaline

42
Q

Cardiac muscle neurotransmitter

A

Ach

43
Q

Cell characteristics of smooth muscle

A

Spindle shaped

44
Q

Cell characteristics of cardiac muscle

A

Cylindrical
Striated
Branched

45
Q

Cell-cell characteristics of smooth muscle

A

Gap junctions in some visceral cells

46
Q

Cell-cell characteristics of cardiac muscle

A

Intercalated discs
Desmosomes
Gap junctions

47
Q

Nuclei of smooth muscle

A

One
Central

48
Q

Nuclei of cardiac muscle

A

One
Central

49
Q

Slow oxidative muscle fibres

A

Type 1

50
Q

Oxidative muscle fibres

A

Type IIa

51
Q

Glycolytic muscle fibres

A

Type IIb

52
Q

Type 1 muscle fibres

A

Aerobic respiration for glucose metabolism
Smaller
Highly vascularised- provide O2
High myoglobin contents
Very high mitochondrial density
Low capacity for glycogen storage
Activity for a long period of time

53
Q

Type IIa muscle fibres

A

Aerobic respiration- metabolising glucose
Larger fibres
High number of blood vessels
High levels of myoglobin
High mitochondrial density
High glycogen storage capacity
Fatigue quickly

54
Q

What gives muscle fibres a bright red colour

A

Myoglobin stores

55
Q

Type IIb muscle fibres

A

Anaerobic respiration fibres
Metabolise glucose
Largest fibres
Low vascularisation
Low myoglobin levels
Low mitochondrial density
Very high glycogen storage capacity
Fatigue fastest

56
Q

Which muscle fibres are the largest

A

Type IIb

57
Q

How is ACh released from the vesicle in synapse

A

SNARE (on vesicle) binds to SNAO and synaptobrevin (on nerve wall)

58
Q

Which muscle fibre has greatest force of contraction

A

Type IIb

59
Q

2 forms of creatine in muscles

A

Creatine - 40%
Phosphocreatine - 60%

60
Q

What enzyme catalyses the synthesis and degradation of phosphocreatine

A

Creatine kinase

61
Q

Creatine at rest

A

Recycled into phosphocreatine in mitochondria

62
Q

Muscle fatigue

A

Progressive weakness of muscle contraction until no response

63
Q

What causes muscle fatigue

A

Decrease in ATP synthesis
Lactic acid levels rise and lower pH of sarcoplasm
Failure of motor neurons to produce ACh due to reduced availability of Ca2+

64
Q

ATP production in fast fibres

A

Hydrolysis of phosphocreatine
Glycolysis - 2 ATP produced (not 38)

65
Q

Which of these is not a contractile cell?

Fibroblast
Myoblast
Myoepithelial cell
Myofibroblast
Pericyte

A

Fibroblast

66
Q

In the sarcomere the dark band A band corresponds to which protein?

A

Myosin

67
Q

Skeletal muscle is striated because…

A

Myofibrils are in register

68
Q

Excitation of the T tubular membrane system causes the concentration of what to rise in the sarcoplasm?

A

Calcium ions

69
Q

The fibro-collagenous connective tissue that binds muscle fibres together to form fascicles is called:

A

Perimysium

70
Q

Which statement concerning muscle fibre types is true?

All muscles contain the same proportion of type 1 and 2 fibres
Exercise increases the proportion of type 2 fibres in a muscle
Postural muscles have a high proportion of type 2 fibres
The proportion of type 1 and 2 fibres in a specific muscle varies between individuals
Type 1 and 2 fibres can be distinguished on H+E

A

The proportion of type 1 and 2 fibres in a specific muscle varies between individuals

71
Q

Skeletal muscles…

Contain a stem cell population
Contain pain receptors
Contract when stimulated by dopamine
Develop from embryonic endoderm
Have a poor blood supply

A

Contain a stem cell population

72
Q

Sharpey’s fibres:

Are made of type 1 collagen
Are specialised muscle fibres
Connect endomysium to bone
Connect bone to bone
Do not penetrate bone

A

Made of type 1 collagen

73
Q

Tendons…

Are richly vascular
Comprise loose fibrous connective tissue
Connect bones to bones
Heal rapidly if injured
May lie in fibrocollagenous sheaths

A

May lie in fibrocollagenous sheaths

74
Q

What might you look for to determine that a structure is a ligament rather than a tendon?

Collagen fibres
Elastin fibres
Fibroblasts
Myocytes
Tendinocytes

A

Elastin fibres

75
Q

Tendiocytes

A

Fibroblasts

MSK (11 decks)

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