Bone & Biomechanics 5

Question 1

Where is the neuromuscular junction positioned?

Answer 1

In the middle third of the muscle fibre

Question 2

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

Answer 2

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

Question 3

What is excitation-contraction coupling?

Answer 3

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

Question 4

Where does the action potential travel?

Answer 4

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

Question 5

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

Answer 5

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

Question 6

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

Answer 6

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

Question 7

Where is the calcium released?

Answer 7

Into the sarcoplasm

Question 8

What does the calcium do?

Answer 8

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

Question 9

What happens to the calcium after it has initiated sliding?

Answer 9

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

Question 10

When does cross bridge cycling occur?

Answer 10

When the calcium ion binds to the myofilaments

Question 11

What is a cross bridge?

Answer 11

When a myosin head is bound to an actin filament

Question 12

What is the natural state of the myofibrils?

Answer 12

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

Question 13

What does ATP do in the cross bridge cycle?

Answer 13

Causes the dissociation of the myosin head from actin

Question 14

What does ATP hydrolysis do?

Answer 14

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

Question 15

What are the products of ATP hydrolysis?

Answer 15

ADP and phosphate which remain bound to the myosin head

Question 16

What happens when the myosin head is cocked?

Answer 16

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

Question 17

What happens after the myosin head is cocked?

Answer 17

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

Question 18

What is the final step of the cross bridge cycle?

Answer 18

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

Question 19

What affects muscle tension?

Answer 19

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

Question 20

What is a twitch?

Answer 20

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)

Question 21

What is a twitch summation?

Answer 21

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

Question 22

What is a tetanus?

Answer 22

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

Question 23

What is meant by the length- tension relationship?

Answer 23

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

Question 24

What happens when the muscle fibre is optimal length?

Answer 24

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

Question 25

What happens when the muscle fibres are stretched?

Answer 25

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

Question 26

What happens when the muscle fibres are slack?

Answer 26

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

Question 27

What does the amount of force developed match?

Answer 27

The situation requiring the force

Question 28

What regulates the number of muscle fibres activated?

Answer 28

The amount of neurons which are active at the same time

Question 29

What is recruitment?

Answer 29

When more motor units are activated to make up more force

Question 30

How many factors does muscle form depend on?

Answer 30

3

Question 31

What factors does muscle form depend on?

Answer 31

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

Question 32

How much can fibres shorten?

Answer 32

Up to 50% of their length

Question 33

What does long muscle fibres give?

Answer 33

A large range of motion

Question 34

What contracts?

Answer 34

Muscle fibres and not the tendons

Question 35

What is another measure of the number of muscle fibres?

Answer 35

Cross-sectional area

Question 36

What is directly proportional to CSA?

Answer 36

The amount of tension and therefore force produced

Question 37

What does a greater number of fibres mean?

Answer 37

Greater CSA and so greater tension

Question 38

What are the two possible arrangements of muscle fibres?

Answer 38

Parallel and pennate

Question 39

What is parallel structure?

Answer 39

Muscle fibres run vertically between the muscle tendons

Question 40

What is pennate structure?

Answer 40

Muscle fibres are arranged oblique to the muscle tendons

Question 41

What is the benefit of parallel arrangement?

Answer 41

Gives a good range of motion as muscle fibres are long

Question 42

What is the disadvantage of parallel arrangement?

Answer 42

Less CSA so therefore less strength

Question 43

What is the benefit of pennate structure?

Answer 43

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

Question 44

What is the disadvantage of pennate structure?

Answer 44

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

Question 45

What are bones when it comes to anatomical levers?

Answer 45

Levers

Question 46

What are joints when it comes to anatomical levers?

Answer 46

Pivot/Fulcrum

Question 47

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

Answer 47

Pull/applied force

Question 48

What is the load when it comes to anatomical levers?

Answer 48

Internal or External

Question 49

What gives the different types of levers?

Answer 49

Where the fulcrum, load and force are positioned

Question 50

What is the positioning of class 1 levers?

Answer 50

Load, fulcrum, applied force

Question 51

What is the positioning of class 2 levers?

Answer 51

fulcrum, load, applied force

Question 52

What is the positioning of class 3 levers?

Answer 52

fulcrum, applied force, load

Question 53

What is an example of a class 1 lever?

Answer 53

Head sitting on neck

Question 54

What is an example of a class 2 lever?

Answer 54

Ankle

Question 55

What is an example of a class 3 lever?

Answer 55

Elbow

Question 56

How many types of muscle action are there?

Answer 56

3

Question 57

What are the three types of muscle action?

Answer 57

Cocentric, eccentric and isometric

Question 58

What occurs in concentric muscle action?

Answer 58

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

Question 59

What occurs in eccentric muscle action?

Answer 59

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

Question 60

What occurs in isometric muscle action?

Answer 60

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

Question 61

How many roles are there for muscles?

Answer 61

4

Question 62

What are the possible roles of muscles?

Answer 62

Agonist, antagonist, stabiliser and neutraliser

Question 63

What is the role of the agonist?

Answer 63

Act concentrically and shorten

Question 64

What is the role of the antagonist?

Answer 64

Act eccentrically and lengthen

Question 65

What is a stabiliser?

Answer 65

When a muscle is active and holding a joint still

Question 66

What muscle action do stabilisers exhibit?

Answer 66

Isometric

Question 67

What is the function of a neutraliser?

Answer 67

To eliminate unwanted movement caused by another muscle

Question 68

What muscle action do neutralisers exhibit?

Answer 68

It depends on the movement occurring

Question 69

Anterior positioned muscles cause...

Answer 69

Flexion

Question 70

Posterior positioned muscles cause...

Answer 70

Extension

Question 71

Medial positioned muscles cause...

Answer 71

Adduction

Question 72

Lateral positioned muscles cause...

Answer 72

Abduction

Question 73

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

Answer 73

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

Question 74

List the 16 muscles needed?

Answer 74

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)

Question 75

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

Answer 75

2 heads which attach to the scapula

Question 76

Where does the bottom of the biceps brachii attach?

Answer 76

Radial tuberosity

Question 77

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

Answer 77

Shoulder flexion, elbow flexion, radioulnar supination

Question 78

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

Answer 78

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

Question 79

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

Answer 79

Shoulder extension and elbow extension

Question 80

What is the shape of the deltoid?

Answer 80

Triangle

Question 81

What does the deltoid attach to?

Answer 81

Clavicle, scapula and humerus

Question 82

What movement(s) are caused by the deltoid?

Answer 82

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

Question 83

What is the structure of the iliopsoas?

Answer 83

psoas major attaches to the vertebrae and joins at the iliacus

Question 84

Where does the iliopsoas sit?

Answer 84

Anteriorly to hip and femur

Question 85

What movement(s) is caused by the iliopsoas?

Answer 85

Hip flexion

Question 86

What does the gluteus maximus attach to?

Answer 86

Hip, sacrum, coccyx and femur

Question 87

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

Answer 87

Hip extension

Question 88

How many heads does the quadriceps femoris have?

Answer 88

Four heads and four muscles

Question 89

What is the position of the rectus femoris?

Answer 89

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

Question 90

Where do the quadriceps femoris muscles attach?

Answer 90

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

Question 91

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

Answer 91

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

Question 92

How many heads does the hamstring have?

Answer 92

2

Question 93

How many sections of the hamstrings are there?

Answer 93

3

Question 94

What movement(s) are caused by the hamstrings?

Answer 94

Flexion of the knee and rotation when flexed

Question 95

What is the position of the tibias anterior?

Answer 95

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

Question 96

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

Answer 96

Ankle dorsiflexion and foot inversion

Question 97

How many heads does the triceps surae have?

Answer 97

3

Question 98

What is the structure of the triceps surae?

Answer 98

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

Question 99

Where do the gastrocnemius and soleus meet?

Answer 99

The Achilles (calcanea tendon)

Question 100

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

Answer 100

Ankle plantar flexion