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Flashcards in MSK Session 2 Deck (117):
0

What two types of muscle are there?

Striated
Non-striated

1

What type of muscle is the diaphragm?

Skeletal

2

Give an example of each type of skeletal muscle arrangement.

Circular: orbicularis oris
Convergent: pec. major
Parallel: sartorius
Unipennate: extensor digitorum longus
Multipennate: deltoid
Fusiform: biceps brachii
Bipennate: rectus femoris

3

How are skeletal muscles attached to bones?

By tendons

4

What does skeletal muscle continually contract?

To maintain posture

5

What is the mechanical efficiency of skeletal muscle?

~20%, rest dissipated as heat

6

What is the gross anatomy of skeletal muscle?

Epimysium --> perimysium --> endomysium
Muscle --> fascicle --> muscle fibre

7

What is fasciculation?

Low level muscle twitch often seen in the face when tired/nervous or more severely in motor neurone disease

8

What is a first class lever?

Where the force and load are on opposite sides of the fulcrum like a see-saw e.g. neck

9

What is a second class lever?

Where the force and load are to the left of the fulcrum like a wheelbarrow e.g. in the foot where the ball is the fulcrum

10

What is a third class lever?

Most common type of lever where the force and load are to the right of the fulcrum, like a fishing rod

11

What can be said about the length along which force acts in a third class lever?

Large

12

What are agonists?

Prime movers

13

What are antagonists?

Oppose prime movers

14

What act together to allow fine, smooth movement?

Agonists and antagonists

15

What are synergists?

Muscles that assist prime movers by neutralising extra motion to keep motion in one direction

16

What are fixators?

Muscles that stabilise the action of prime movers by fixing non-moving joints when prime mover is acting over two joints

17

What are compartments?

Groups of muscles surrounded by connective tissue

18

What is compartment syndrome?

When pressure builds up inside a compartment due to the inability of the surrounding CT to undergo rapid expansion and causes nerve compression

19

What can cause compartment syndrome?

Bleeding

20

What effect can long-term training have on the connective tissue surrounding a compartment?

Expansion

21

What is isotonic muscle contraction?

Constant tension with variable muscle length that changes to move a load

22

What happens in concentric isotonic muscle contraction?

Muscle shortens

23

What happens in eccentric isotonic muscle contraction?

Muscle exerts force whilst extended e.g. walking downhill

24

What is isometric muscle contraction?

Muscle remains a constant length but has variable tension

25

Describe isometric contraction in hand grip.

Forearm muscles do not change length but exert force
Small muscles also used which rapidly increase BP - risky for elderly and hypertensive

26

What are the three types of muscle fibre?

Type I - slow oxidative
Type IIa - fast oxidative
Type IIb - fast glycolytic

27

What is used to identify muscle type?

Mitochondrial staining on post mortem/needle biopsy sample

28

What characterises slow oxidative muscle?

Aerobic
High myoglobin levels
Red colour
Lots of mitochondria
Rich capillary supply
Fatigue resistant - used in endurance activities and posture

29

What characterises fast oxidative muscle?

Aerobic
High myoglobin levels
Red to pink colour
Many mitochondria
Rich capillary supply
Moderate fatigue resistance - used for walking and sprinting

30

What characterises type IIb muscle?

Anaerobic glycolysis
Low myoglobin levels
White (pale) colour
Few mitochondria
Poorer capillary supply
Rapidly fatiguable - used for short intense movement

31

What is proprioception?

Awareness of self

32

How do specialised muscle fibres in the belly of a muscle allow proprioception to take place?

Sense stretch and send signals back to brain reporting tension and strain levels in the muscle

33

What can be considered as the feedback control of movement as well as feedback from the joints?

Proprioception

34

What is a motor unit?

Motor neurone and the muscle fibre it innervates

35

Where is the output of a motor neurone?

Through ventral root

36

How does the number of muscle fibres controlled by a motor neurone vary with control?

More control = fewer fibres innervated by a single neurone

37

What is cross talk?

Method of communication b/w neurones and muscle using signalling molecules

38

How does atrophy of a neurone or a muscle cause atrophy of its corresponding component?

Signals are either not released or not needed

39

Which signalling molecule maintains communication b/w motor neurone and muscle and is very important in the NMJ?

Neutrophin-3

40

What causes baseline muscle tone in muscles at rest?

Motor neurone activity
Muscle elasticity due to protein content

41

What controls baseline muscle tone?

Motor control centres in the brain
Afferent fibre signals originating from the muscle

42

What is hypotonia?

Low level of muscle tone

43

What can cause hypotonia?

Primary degradation of the muscle
Lesions of cerebellum and cerebral/shock causing damage to motor cortex involved in feedback mechanism
Lesion of sensory afferents from the muscle spindles
Lesions of lower motor neurones e.g. polyneuritis
Spinal neural shock

44

What does polyneuritis affect?

Multiple motor neurones in body in different places

45

How is ACh exocytosed from the NMJ?

AP sweeps around membrane --> opens calcium channels --> calcium in

46

What happens when 2 ACh bind to the alpha-subunit of nicotinic receptors on the effector muscle?

Conformational change of ligand gated sodium --> sodium in --> depolarisation --> calcium release from SR

47

Why are anaesthetics used?

Less tissue damage is caused if the tissue is relaxed

48

What is given in addition to anaesthetics to counteract the initial contraction they cause by inhibiting AChE?

Neuromuscular block

49

What is spatial summation?

Type of recruitment learned throughout life

50

How does spatial summation work?

More motor neurones are activated so more muscle fibres are recruited to develop more force

51

Where do reflex pathways in spatial summation come from?

Muscle spindles
Joint receptors
Golgi tendon organs of muscle fibres

52

What do Golgi tendon organs sense?

Changes in muscle tension

53

What is temporal summation?

Recruitment where increased frequency of AP to muscle fibres causes summation

54

What is the difference between fused and infused tetanus?

Unfused = twitch
Fused = continuous force = no relaxation

55

What is present in all soil that interferes with feedback control of muscle tension to cause continual contraction?

Clostridium tetani

56

What is electromyography?

Electrodes placed above/in muscles to record their electrical activity

57

Why is the amplitude in an electromyography equivalent to the force of contraction?

Increased recruitment of motor units

58

What is seen in an EMG that indicates MND?

Graph doesn't match up

59

How is relaxation of a muscle achieved by lower cytoplasm calcium content?

Pumping calcium back into SR via calcium pumps
Binding to calmodulin

60

What are sources of energy for muscle contraction?

Short term ATP stores in muscle fibre
Creatine phosphate
Aerobic and anaerobic glycolysis
Oxidative phosphorylation

61

What energy source for muscle contraction can be measured for suspected muscle damage?

Creatine phosphate

62

How does anaerobic glycolysis cause muscle cramp?

Conversion by LDH of pyruvate to lactate which acts on nerve endings coupled with a decrease in pH

63

When does peripheral fatigue occur?

Muscle glycogen stores are depleted
Within one minute of blood flow interruption

64

What is contracture?

State of continuous contraction when ATP is depleted

65

What causes rigor mortis?

Myosin X-bridges unable to detach from actin filaments

66

What is the time frame of rigor mortis?

Slow onset, peaks at 12-13 hours and can give v. exact time of death

67

What forms the anterior border of the axilla?

Pec. minor and major

68

What makes up the medial border of the axilla?

Serratus anterior
Thoracic wall

69

What forms the posterior border of the axilla?

Scapularis
Teres major
Latissimus dorsi

70

What forms the lateral border of the axilla?

Intertubecular sulcus

71

What forms the apex of the axilla?

Cervico-axillary canal bounded by the first rib, clavicle and superior edge of scapula a

72

What transverses the apex of the axilla?

Arteries
Veins
Lympahtics
Nerves

73

What forms the base of the axilla?

Concave skin
Subcutaneous tissue
Axillary fascia from 4th rib to axillary fossa

74

What enters and leaves the clavipectoral triangle?

Cephalic vein enters
Medial and lateral pectoral nerves leave

75

What is found in the quadrangular space?

Post-circumflex humeral artery
Axillary nerve

76

What is the main artery supplying the upper limb?

Axillary artery

77

What are the parts of the axillary artery?

Medial, posterior and lateral to pec. minor

78

Describe the path of the axillary artery.

Lateral border of 1st rib --> medial border of pec. minor --> lateral border of pec. minor --> inferior border of teres major

79

What arteries branch off from the axillary artery?

Super thoracic
Thoraco-acromial
Lateral thoracic
Subscapula artery
Anterior and posterior circumflex humeral arteries

80

What is the collateral route enabling venous return if IVC is obstructed?

Thoraco-epigastric veins

81

Brachial and basilic vein --> subclavian vein --> second part of axillary vein --> initial distal end

Describe the path of the axillary vein.

82

Which veins drain into the axillary vein?

Thoraco-epigastric
Cephalic
Corresponding veins to the thoraco-acromial artery

83

Moving anteriorly to posteriorly in the axilla, how are the artery, nerve and vein arranged?

Vein
Artery
Nerve
(VAN)

84

What 5 groups of lymph nodes are present in the axilla?

Pectoral
Subscapular
Humeral
Central
Apical

85

Where are the pectoral lymph nodes found and what area do they drain?

3-5 nodes on medial wall
Breast

86

Where are the subscapular lymph nodes located and what do they drain?

6-7 nodes on posterior axillary fold
Posterior wall and scapula

87

Where are the humeral lymph nodes found and what do they drain?

4-6 nodes on lateral wall
UL

88

Where are central and apical lymph nodes found?

Central = 3-4 nodes deep to pec. minor
Apical = all other groups and lympahtics not already classified

89

What are the components of the brachial plexus?

Roots
Trunks
Divisions
Cords
Terminal branches

90

Where do the roots of the brachial plexus arise?

Paired spinal nerves that leave the spinal cord via the intervertebral foramen of the vertebral column which divide into an anterior part

91

What is the fate of the posterior division of the spinal nerves that have left the spinal cord?

Innervate skin and musculature of the trunk

92

What do the roots of the brachial plexus pass between to enter the base of the neck?

Anterior and medial scalene muscles

93

What happens in the brachial plexus at the base of the neck?

Roots converge to form three trunks

94

What path do the trunks of the brachial plexus take?

Move laterally crossing the posterior triangle of the neck

95

What happens to the brachial plexus within the posterior triangle of the neck?

Each trunk divides into anterior and posterior branches

96

What path do the divisions of the brachial plexus take?

Pass into the axilla

97

What happens to the brachial plexus in the axilla?

Divisions combine to form three nerves which are the cross of the brachial plexus

98

What are the cords of the brachial plexus named relative to?

Axillary artery

99

What do the cords of the brachial plexus give rise to?

Major branches

100

What happens to the brachial plexus in the axilla and proximal part of the UL?

3 cords become 5 branches

101

What is the function of the five major branches of the brachial plexus?

Provide innervation to the muscle and skin they pass over

102

What are the five major branches of the brachial plexus?

Ulnar nerve
Radial nerve
Median nerve
Axillary nerve
Musculocutaneous nerve

103

What are the nerve roots of the ulnar nerve?

C8 and T1

104

What are the nerve roots of the radial nerve?

C5-8 and T1

105

What are the nerve roots of the median nerve?

C6-8 and T1

106

What are the nerve roots of the axillary nerve?

C5 and 6

107

What are the nerve roots of the musculocutaneous nerve?

C5-7

108

What does the ulnar nerve innervate?

Muscles of hand
Flexor carpi ulnaris
Medial half of flexor digitorum profundus
Sense in anterior and posterior medial 1.5 fingers and palm area

109

What does the radial nerve innervate?

Triceps brachii
Extensor muscles in posterior compartment of forearm
Sense in posterior aspect of arm and forearm
Sense in posterior and lateral aspect of hand

110

What does the median nerve innervate?

Flexor muscles in forearm
Thenar muscles
2 lateral lumbricals that move index and middle fingers
Sense in lateral palm and lateral 3.5 fingers on palmar surface of hand

111

What branches does the median nerve give rise to?

Palmar cutaneous branch
Digital cutaneous branch

112

What does the axillary nerve innervate?

Deltoid
Teres major
Long head of biceps brachii
Sense in regimental badge area

113

What branch does the axillary nerve give rise to?

Superior lateral cutaneous nerve of arm

114

What does the musculocutaneous nerve innervate?

Brachialis
Biceps brachii
Corachobrachialis
Sense in lateral half of anterior forearm and small lateral portion of posterior forearm

115

What branch does the musculocutaneous nerve give rise to?

Lateral cutaneous branch of forearm

116

What shape do the musculocutaneous, median and ulnar nerve form in the brachial plexus?

M