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HUBS191 > Bone & Biomechanics 5 > Flashcards

Bone & Biomechanics 5 Flashcards

1
Q

Where is the neuromuscular junction positioned?

A

In the middle third of the muscle fibre

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2
Q

What is the reason for the position of the neuromuscular junction?

A

So that the wave of depolarisation(action potential) spreads over the sarcolemma and propagates the whole fibre

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3
Q

What is excitation-contraction coupling?

A

The term used to describe the steps from plasma membrane excitation to calcium release to muscle excitation

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4
Q

Where does the action potential travel?

A

After it has reached the neuromuscular junction it causes depolarisation and travels along the sarcolemma and down the transverse tubule

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5
Q

What happens once the action potential is inside the transverse tubule?

A

The change in membrane potential because of depolarisation is sensed by the voltage sensor

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6
Q

What does the voltage sensor do once it senses the action potential?

A

It makes contact with the ryanodine receptor found on the sarcoplasmic reticulum terminal cisternae and this triggers the release of calcium ions from the channel in the SR

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7
Q

Where is the calcium released?

A

Into the sarcoplasm

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8
Q

What does the calcium do?

A

It binds to the contractile apparatus which then initiates the sliding to produce tension and force for contraction

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9
Q

What happens to the calcium after it has initiated sliding?

A

It unbinds from the contractile apparatus and is pumped back into the SR by SERCA which uses ATP energy. This then causes the muscles to relax

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10
Q

When does cross bridge cycling occur?

A

When the calcium ion binds to the myofilaments

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11
Q

What is a cross bridge?

A

When a myosin head is bound to an actin filament

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12
Q

What is the natural state of the myofibrils?

A

There is a myosin head attached to actin and the calcium ion levels are very low

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13
Q

What does ATP do in the cross bridge cycle?

A

Causes the dissociation of the myosin head from actin

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14
Q

What does ATP hydrolysis do?

A

Causes a shape change so that the myosin head is cocked and moved from where it initially was

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15
Q

What are the products of ATP hydrolysis?

A

ADP and phosphate which remain bound to the myosin head

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16
Q

What happens when the myosin head is cocked?

A

It is put in line with a new binding site on the actin filament

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17
Q

What happens after the myosin head is cocked?

A

It binds to the new actin site and the power stroke occurs (head flexes) generating the force to pull the thin filament towards the centre of the sarcomere and initiate contraction of the myofilaments

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18
Q

What is the final step of the cross bridge cycle?

A

Another ATP molecule binds to the myosin head and causes dissociation from the actin and the process to repeat

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19
Q

What affects muscle tension?

A

The rate at which muscle is stimulated (action potential is delivered) and the number of muscle fibres recruited (used to generate force)

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20
Q

What is a twitch?

A

A twitch occurs when a single action potential results in a pulse of calcium ions being released into the sarcoplasm and a short period of tension development (contraction)

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21
Q

What is a twitch summation?

A

This occurs when a muscles fibre is restimulated before I is completely relaxed so the second twitch adds to the first

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22
Q

What is a tetanus?

A

This occurs when many action potentials are fired in a rapid sequence and there is a sustained release of calcium from the SR, a sustained period of actin-myosin interaction and a sustained period of contraction

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23
Q

What is meant by the length- tension relationship?

A

Each muscle has an optimal length where it will be strongest and when longer or shorter than that length it will be weaker

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24
Q

What happens when the muscle fibre is optimal length?

A

It causes optimal overlap for myosin heads to make contact with the actin filament

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25
Q

What happens when the muscle fibres are stretched?

A

It causes very little overlap so it is difficult for actin-myosin interaction to occur

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26
Q

What happens when the muscle fibres are slack?

A

It causes too much overlap and doesn’t allow for much cross bridging to occur

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27
Q

What does the amount of force developed match?

A

The situation requiring the force

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28
Q

What regulates the number of muscle fibres activated?

A

The amount of neurons which are active at the same time

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29
Q

What is recruitment?

A

When more motor units are activated to make up more force

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30
Q

How many factors does muscle form depend on?

A

3

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31
Q

What factors does muscle form depend on?

A

Length of muscle fibres, number of muscle fibres and arrangement of muscle fibres

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32
Q

How much can fibres shorten?

A

Up to 50% of their length

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33
Q

What does long muscle fibres give?

A

A large range of motion

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34
Q

What contracts?

A

Muscle fibres and not the tendons

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35
Q

What is another measure of the number of muscle fibres?

A

Cross-sectional area

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36
Q

What is directly proportional to CSA?

A

The amount of tension and therefore force produced

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37
Q

What does a greater number of fibres mean?

A

Greater CSA and so greater tension

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38
Q

What are the two possible arrangements of muscle fibres?

A

Parallel and pennate

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39
Q

What is parallel structure?

A

Muscle fibres run vertically between the muscle tendons

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40
Q

What is pennate structure?

A

Muscle fibres are arranged oblique to the muscle tendons

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41
Q

What is the benefit of parallel arrangement?

A

Gives a good range of motion as muscle fibres are long

42
Q

What is the disadvantage of parallel arrangement?

A

Less CSA so therefore less strength

43
Q

What is the benefit of pennate structure?

A

More fibres fit into the space so there is increased CSA and strength

44
Q

What is the disadvantage of pennate structure?

A

Reduced shortening and therefore range of motion because muscle fibres only shorten to 50% of the length of the shortest fibre

45
Q

What are bones when it comes to anatomical levers?

A

Levers

46
Q

What are joints when it comes to anatomical levers?

A

Pivot/Fulcrum

47
Q

What is the muscle contraction when it comes to anatomical levers?

A

Pull/applied force

48
Q

What is the load when it comes to anatomical levers?

A

Internal or External

49
Q

What gives the different types of levers?

A

Where the fulcrum, load and force are positioned

50
Q

What is the positioning of class 1 levers?

A

Load, fulcrum, applied force

51
Q

What is the positioning of class 2 levers?

A

fulcrum, load, applied force

52
Q

What is the positioning of class 3 levers?

A

fulcrum, applied force, load

53
Q

What is an example of a class 1 lever?

A

Head sitting on neck

54
Q

What is an example of a class 2 lever?

A

Ankle

55
Q

What is an example of a class 3 lever?

A

Elbow

56
Q

How many types of muscle action are there?

A

3

57
Q

What are the three types of muscle action?

A

Cocentric, eccentric and isometric

58
Q

What occurs in concentric muscle action?

A

Muscle is active and tension is developed, change in joint position (angle), muscle shortens

59
Q

What occurs in eccentric muscle action?

A

Muscle is active and tension is developed, change in joint position (angle), muscle lengthens

60
Q

What occurs in isometric muscle action?

A

Muscle is active and tension is developed, no change in joint position, no change in length of muscle

61
Q

How many roles are there for muscles?

A

4

62
Q

What are the possible roles of muscles?

A

Agonist, antagonist, stabiliser and neutraliser

63
Q

What is the role of the agonist?

A

Act concentrically and shorten

64
Q

What is the role of the antagonist?

A

Act eccentrically and lengthen

65
Q

What is a stabiliser?

A

When a muscle is active and holding a joint still

66
Q

What muscle action do stabilisers exhibit?

A

Isometric

67
Q

What is the function of a neutraliser?

A

To eliminate unwanted movement caused by another muscle

68
Q

What muscle action do neutralisers exhibit?

A

It depends on the movement occurring

69
Q

Anterior positioned muscles cause…

A

Flexion

70
Q

Posterior positioned muscles cause…

A

Extension

71
Q

Medial positioned muscles cause…

A

Adduction

72
Q

Lateral positioned muscles cause…

A

Abduction

73
Q

What is the exception to the concentric actions of muscles rule?

A

The knee as it flexes posteriorly, anterior positioned muscles cause extension and posterior positioned muscles cause flexion

74
Q

List the 16 muscles needed?

A

Biceps brachii, triceps brachii, deltoid, iliopsoas (psoas major and iliacus), gluteus maximus, quadriceps femoris (rectus femoris, vasts lateralis, vasts intermedius, vasts medialis), Hamstrings (biceps femoris, semi-membranosus, smi-tendinosus), tibialis anterior, triceps surae (gastrocnemius and soleus)

75
Q

How many heads does the biceps brachii have and where do they attach?

A

2 heads which attach to the scapula

76
Q

Where does the bottom of the biceps brachii attach?

A

Radial tuberosity

77
Q

What movement(s) are caused by the biceps brachii?

A

Shoulder flexion, elbow flexion, radioulnar supination

78
Q

How many heads does the triceps brachii have and where do they attach?

A

3 heads- long heads attach to scapula and lateral and medial heads attach to the humerus

79
Q

What movement(s) are caused by the triceps brachii?

A

Shoulder extension and elbow extension

80
Q

What is the shape of the deltoid?

A

Triangle

81
Q

What does the deltoid attach to?

A

Clavicle, scapula and humerus

82
Q

What movement(s) are caused by the deltoid?

A

Shoulder flexion by the anterior fibres, shoulder abduction by the lateral fibres and shoulder extension by the posterior fibres

83
Q

What is the structure of the iliopsoas?

A

psoas major attaches to the vertebrae and joins at the iliacus

84
Q

Where does the iliopsoas sit?

A

Anteriorly to hip and femur

85
Q

What movement(s) is caused by the iliopsoas?

A

Hip flexion

86
Q

What does the gluteus maximus attach to?

A

Hip, sacrum, coccyx and femur

87
Q

What movement(s) is caused by the gluteus maximus?

A

Hip extension

88
Q

How many heads does the quadriceps femoris have?

A

Four heads and four muscles

89
Q

What is the position of the rectus femoris?

A

It sits superficially and runs straight along the femur, also attaching to the hip

90
Q

Where do the quadriceps femoris muscles attach?

A

To the patella and the patella ligament attaches to the tibial tuberosity so the quadriceps are attached to the knee

91
Q

What movement(s) are caused by the quadriceps femoris?

A

Knee extension, and the rectus femoris also flexes the hip because it is the only part touching the hip joint

92
Q

How many heads does the hamstring have?

A

2

93
Q

How many sections of the hamstrings are there?

A

3

94
Q

What movement(s) are caused by the hamstrings?

A

Flexion of the knee and rotation when flexed

95
Q

What is the position of the tibias anterior?

A

It doesn’t cross the knee, runs anterior to the ankle and to the medial portion of the foot

96
Q

What movement(s) is caused by the tibias anterior?

A

Ankle dorsiflexion and foot inversion

97
Q

How many heads does the triceps surae have?

A

3

98
Q

What is the structure of the triceps surae?

A

Superficial gastrocnemius has 2 heads which attach to the femur while the deep soleus has one which attaches to the tibia/fibula

99
Q

Where do the gastrocnemius and soleus meet?

A

The Achilles (calcanea tendon)

100
Q

What movement(s) is caused by the triceps surae?

A

Ankle plantar flexion

HUBS191 (29 decks)

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