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Musculoskeletal system > Muscle structure and function > Flashcards

Muscle structure and function Flashcards

1
Q

What are the three types of muscle?

A

Skeletal, smooth and cardia

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2
Q

Characteristics of skeletal muscle

A

Voluntary and striated , attached to bones

Long, cylindrical, multinucleate

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3
Q

Characteristics of cardiac muscle

A

Striated and found in walls of heart

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4
Q

Characteristics of smooth muscle

A

Involuntary/visceral found in walls of hollow organs

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5
Q

What are the three main functions of muscle?

A

Movement, support and heat production

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6
Q

Characteristics of spinal nerves

A

Part of somatic nervous system
31 pairs of spinal nerves
Sensory (afferent) and motor (efferent)

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7
Q

What is a myotome?

A

Group of muscles innervated by a single spinal nerve

Skeletal muscles innervated by spinal nerves derived from the same segmental level of the spinal cord as the somite

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8
Q

How does the musculoskeletal system develop?

A

Paraxial mesoderm form segmented blocks called epithelial somites
Under notochord influence, each somite block reorganises into 3 groups of progenitor tissue cells:
Dermatome, myotome and sclerotome

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9
Q

What are epithelial somites?

A

Blocks of neural tube located on either side of the neural tube in the developing embryo

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10
Q

How do dermatomes assist the development of the musculoskeletal system?

A

Give rise to connective tissue and dermis of skin

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11
Q

How do myotomes assist in the development of the musculoskeletal system?

A

Develop skeletal muscle (dorsal and ventrolateral muscles of body wall)

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12
Q

How do sclerotomes assist in the development of the musculoskeletal system?

A

Give rise to vertebrae and rib cage

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13
Q

Where is most smooth muscle derived from?

A

Lateral plate mesoderm and neural crest (gut develops from splanchic mesoderm)

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14
Q

Where is most cardiac muscle derived from?

A

Splanchnic (visceral) layer of lateral plate mesoderm surrounding developing heart tissue

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15
Q

Where is most skeletal muscle derived from?

A

Each myotome, receiving its nerve supply from the spinal nerves derived from the same segmental level of the spinal cord as the somite

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16
Q

Diameter and length of skeletal muscle fibres

A

10-100 micrometres, length is up to 35 cm

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17
Q

What is a motor unit?

A

A group of muscle fibres with one single motor neurone supplying them

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18
Q

What are the specialised stretch receptors in skeletal muscle?

A

Neuromuscular spindle

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19
Q

How many motor neurone innervate a muscle fibre?

A

One, but a neurone could connect to many muscle fibres

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20
Q

How many muscle fibres are in motor unit 2?

A

3

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21
Q

How many muscle fibres are in motor unit 1?

A

2

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22
Q

Size variation in motor units

A

From 2-3 in larynx to 2000-3000 in gastrocnemius muscle

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23
Q

What do tendons do?

A

Attach muscle to bone

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24
Q

What happens to tendons when they approach muscle?

A

They turn into epimysium, which surrounds the muscle

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25
Q

What are muscle fascicles made up of?

A

Bundles of cells called muscle fibres

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26
Q

What is the endomysium?

A

The connective tissue layer surrounding muscle fibres

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27
Q

What are the nuclei like in muscle fibres?

A

Located peripherally under the endomysium

Multinucleated - many myoblasts fuse together to form a single cell

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28
Q

Which nerve innervated muscle fibres?

A

Motor neuron

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29
Q

Which blood vessel supplies muscle fibres?

A

Arteriole

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30
Q

Why can muscle fibres contract?

A

Full of proteins - myofibrils made of filamentous proteins (myosin and actin)

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31
Q

Why are myofibrils striated?

A

Overlapping layers of protein fibres

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32
Q

What is the sarcolemma?

A

Muscle fibre cell membrane

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33
Q

What are T-tubules?

A

Pits in the sarcolemma which connect the outer environment to the nucleus
Conducts electrical impulse to nucleus

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34
Q

Which organelle does the SR closely resemble?

A

It’s a modified version of the smooth ER

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35
Q

Muscles in the anterior/flexor compartment of the arm

A

Coracobrachialis
Biceps Brachii
Brachialis

36
Q

Muscle in the posterior/extensor compartment of the arm

A

Triceps

37
Q

Muscles in the posterior/extensor compartment of the forearm

A

Brachioradialis, extensor carpi radialis longus, superficial and deep layer muscles

38
Q

What are the 6 symptoms of compartment syndrome beginning with P?

A 
Pain
Palpably tense compartment 
Pain with passive stretch
Paraesthesia 
Paralysis
Pulselesness/pallor
39
Q

What are the three types of biomechanics levers?

A

First/second/third

40
Q

Equation for torque

A

Torque = effort x distance

41
Q

What is a first order lever?

A

Fulcrum is in middle
Load is pushing down and on left
Effort is pushing down on right

42
Q

What is a second order lever?

A

Fulcrum is pushing down on right, load is pushing down in middle, effort is pushing up on right

43
Q

What is a third order lever?

A

Load is pushing down on left
Effort is pushing up in middle
Fulcrum is pushing down on right

44
Q

Rhyme for remembering levers

A

1,2,3

F,L,E (in middle)

45
Q

3 examples of agonists vs antagonists

A

Flexors vs extensors
Abductors vs adductors
Pronator vs supinator

46
Q

How does the arrangement of fascicles impact the lever?

A

Greater number of muscle fibres = greater power

Longer and more parallel arrangement = more muscle shortening

47
Q

What are the 7 types of fascicle arrangement?

A 
Circular
Convergent
Parallel
Unipennate
Multipennate
Fusiform
Bipennate
48
Q

What is synergistic actions?

A

Synergistic muscles contract to prevent unwanted movement or aid the muscle of the agonist

49
Q

Why does winged scapula occur?

A

Paralysis of the serratus anterior muscle due to damage of long thoracic nerve

50
Q

What are the three phrases used to describe the direction of a muscle?

A

Rectus
Transverse
Oblique

51
Q

What direction is a rectus muscle facing?

A

Straight/parallel to midline

52
Q

What direction is a transverse muscle facing?

A

Perpendicular to midline

53
Q

What direction is an oblique muscle facing?

A

Diagonal to midline

54
Q

What are the four phrases used to describe the size of a muscle?

A

Maximus/minimus
Longus
Major/minor
Brevis

55
Q

Which 7 factors should you consider when naming muscle?

A 
Direction 
Size
Shape
Action
Number of origins
Location
Origin and insertion
56
Q

How many heads does a bicep/tricep/quadricep muscle have?

A

2/3/4

57
Q

What is neuromuscular disease?

A

Disease/damage of somatic motor neurone, neuromuscular junctions or muscle fibres

58
Q

What is myasthenia Gravis?

A

Autoimmune damage to NMJ - causes muscle weakness and fatigue

59
Q

What is myopathy?

A

Disease/disorder of skeletal muscle tissue

60
Q

What is Duchenne’s/Becker’s muscular dystrophy?

A

x-linked inherited skeletal; muscle fibre degenerative disease - causes muscle weakness and wasting mainly in boys

61
Q

How does Duchenne’s/Becker’s muscular dystrophy develop?

A

Dystrophin gene mutates - loses structural link between sarcolemma and sarcomere
Dystrophin binds to actin and Marco-glyco complex
Sarco-glyco complex has links to basal lamina - provides tensile strength
Muscles contract and pull apart

62
Q

What is Gower’s sign?

A

Struggling to get up from floor

63
Q

Difference between Duchenne and Becker’s muscular dystrophy?

A

Duchenne’s is complete break between sarcolemma and collagen in basement membrane
Becker’s = partial expression of dystrophin (normally shorter)
Duchenne victims tend to die younger because diaphragm stops working

64
Q

What is muscular hypertrophy?

A

Skeletal muscle growth after birth occur through enlargement of existing muscle cells - a process called hypertrophy. This is influenced by hormones and exercise

65
Q

What is sarcopenia?

A

Reduction in muscle mass due to ageing - influenced by reduced hormonal signalling, reduced nervous stimulation, muscle disuse, protein synthesis and diet

66
Q

What is creatine phosphate?

A

An amino acid bound to a phosphate group

Donates phosphate to ATP via creatine kinase

67
Q

What is creatine kinase?

A

Enzyme that stimulates creatine phosphate to donate phosphate to ATP

68
Q

What are kinases?

A

Enzymes that can phosphorylate

69
Q

Is the process of phosphorylation reversible?

A

Yes

70
Q

Which enzyme functions in mitochondrion to add phosphate group to phosphocreatine?

A

mtCK (mitochondrial creatine kinase)

71
Q

What happens to phosphate in the cytosol of the mitochondria to stimulate contraction?

A

Muscle isoform of creatine kinase uses phosphocreatine to donate phosphate group to ATP
Myosin heads use phosphate
ATP used by myosin heads and can be used by SERCA pump to push calcium into SR

72
Q

Characteristics of cardiomyocytes

A

Single cells, 1 or 2 nuclei located centrally, have darker regions that are intercalated disks (separate cells)

73
Q

Which molecules form a diad?

A

T tubules and SR

74
Q

What do gap junctions do?

A

Allow sarcoplasm to be shared between cardiomyocytes

75
Q

What does MLCK stand for?

A

Myosin Light Chain Kinase

76
Q

What does Tm stand for?

A

Tropomyosin

77
Q

Characteristics of smooth muscle

A

Single cells with one centrally located nucleus and sheaths of basal lamina
No troponin complexes
Have smooth muscle myosin to turn into actin-binding structure when it has light chain of myosin phosphorylate

78
Q

Which enzyme phosphorylates the light chain of smooth muscle?

A

MLCK

79
Q

What is MLCK activated by?

A

Calcium

80
Q

How does calcium activate MLCK?

A

When calcium enters smooth muscle it binds to calmodulin and activates calmodulin kinases to phosphorylate MLCK

81
Q

What is a tendon?

A

A thick band of dense connective tissue that attaches muscle to bone

82
Q

What is aponeurosis?

A

Broad sheet of dense connective tissue that attaches muscles to bone

83
Q

What is the muscle attachment site origin?

A

Attachment site of muscle tendon/aponeurosis to less moveable or stationary bone

84
Q

What is the muscle attachment site insertion?

A

Attachment site of muscle tendon/aponeurosis to more moveable bone

85
Q

What is muscle group action?

A

A coordinated contraction of a group of muscles to bring about movement of body parts - several skeletal muscles often act as a group to effect movement of body parts

Musculoskeletal system (24 decks)

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