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JL Musculoskeletal > Physiology > Flashcards

Physiology Flashcards

1
Q

What two muscle types are striated?

A

Skeletal and cardiac

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2
Q

What is muscle striation caused by?

A

Alternating dark bands of myocin (thick filaments) and light bands of actin (thin filaments)

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3
Q

What are skeletal muscle fibres organised into?

A

Motor units

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4
Q

What is a motor unit?

A

A single alpha motor neuron and all the skeletal muscle fibres it innervates.

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5
Q

What is the relationship between number of muscle fibres per motor unit and function of muscle?

A

Muscles which serve fine movements have fewer fibres per motor unit.

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6
Q

Give three examples of fine movement muscles?

A
  1. External eye muscles
  2. Muscles of facial expression
  3. Intrinsic hand muscles
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7
Q

What makes up myofibrils?

A

Sacromeres

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8
Q

What type of initiation of contraction is involved in skeletal muscle?

A

Neurogenic

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9
Q

What type of initiation of contraction is involved in cardiac muscle?

A

Myogenic

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10
Q

What type of muscle has motor units, no gap junctions but has neuromuscular junctions present?

A

Skeletal

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11
Q

What type of muscle has no neuromuscular junction but has gap junctions?

A

Cardiac

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12
Q

In skeletal muscle contraction - where does the calcium come entirely from?

A

Sarcoplasmic reticulum

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13
Q

In cardiac muscle contraction - where does the calcium come from?

A

ECF and sarcoplasmic reticulum

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14
Q

What is the process whereby the surface action potential results in activation of the contractile mechanism of the muscle fibre?

A

Excitation contraction coupling

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15
Q

In skeletal muscle - when is the calcium released from the lateral sacs of the sarcoplasmic reticulum?

A

When the surface action potential spreads down the transverse T-tubules

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16
Q

What is the transmitter at the neuromuscular junction?

A

Acetylcholine

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17
Q

What is the functional unit of skeletal muscle?

A

Sacromeres

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18
Q

What is the smallest component capable of performing all the function of that organ called?

A

Functional unit

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19
Q

Where is the sacromere found between?

A

Two Z-lines

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20
Q

What do Z-lines connect?

A

The thin filaments of 2 adjoining sacromeres

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21
Q

What is the A-band made up from?

A

Thick filaments along with portions of thin filaments that overlap in both ends of thick filaments

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22
Q

What is the name for the lighter area within middle of A-band where thin filaments do not reach?

A

H-zone

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23
Q

What line extends vertically down the middle of A-band within centre of H-zone?

A

M-line

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24
Q

What does the I-band consist of?

A

Remaining portion of thin filaments that do not project in A-band

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25
Q

How is muscle tension produced?

A

By sliding of actin filaments on myocin filaments

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26
Q

What is required for both contraction and relaxation of muscle fibres?

A

ATP

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27
Q

What is required to switch on cross bridge formation?

A

Calcium

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28
Q

What two primary factors does gradation of skeletal muscle tension depend on?

A
  1. Number of muscle fibres contracting within the muscle

2. Tension developed by each contracting muscle fibre

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29
Q

What allows simultaneous contraction of a number of muscle fibres?

A

Motor units

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30
Q

A stronger contraction could be achieved by stimulation of more motor units - what is this known as?

A

Motor unit recruitment

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31
Q

During submaximal contractions - what helps prevent muscle fatigue?

A

A synchronous motor units

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32
Q

What three factors does tension developed by each contracting muscle fibre depend on?

A
  1. Frequency of stimulation
  2. Summation of contractions
  3. Length of muscle fibres
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33
Q

In skeletal muscle: what is the duration of action potential much shorter than?

A

Duration of resulting twitch

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34
Q

What does repetitive fast stimulation of skeletal muscle bring about?

A

Summates twitches to bring about a stronger contraction

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35
Q

If a muscle fibre is restimulated after it has completely relaxed, what length is the is the second twitch?

A

Same magnitude as first twitch

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36
Q

If a muscle fibre is restimulated before it has completely relaxed, what happens?

A

Second twitch is added onto the first resulting in summation

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37
Q

What occurs when a muscle fibre is stimulated so rapidly that it does not have an opportunity to relax at all between stimuli?

A

A maximal sustained contraction known as tetanus occurs

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38
Q

Can cardiac muscle be tetanised? Explain.

A

No - the long refractory period prevents generation of tetanic contraction

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39
Q

When can maximal tetanic contraction be achieved?

A

When muscle is at its optimal length before the onset of contraction.

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40
Q

In teh body the resting length of a skeletal muscle is approximally what?

A

Its optimal length

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41
Q

What is isotonic contraction used for?

A

Body movements and for moving objects - muscle tension remains constant as the muscle length changes

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42
Q

What are isometric contractions used for?

A

Supporting objects in fixed positions and for maintaining body posture - muscle tension develops at constant muscle length.

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43
Q

In both isotonic and isometric contractions muscle tension is transmitted to the bone via what?

A

Elastic components of muscle

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44
Q

The velocity of muscle shortening decreases as the load what?

A

Increases

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45
Q

What four things could cause impairment of skeletal muscle function

A
  1. Intrinsic disease of muscle
  2. Disease of NMJ
  3. Disease of lower motor neurones which supply the muscle
  4. Disruption of inputs to motor unit
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46
Q

Give 3 examples of genetically determined myopathies that cause intrinsic muscle disease?

A
  1. Congenital myopathies
  2. Muscular dystrophy
  3. Myotonia
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47
Q

Give a disease which involves chronic degeneration of contractile elements?

A

Muscular dystrophy

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48
Q

Give a disease which involves abnormalities in muscle membrane ion channels?

A

Myotonia

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49
Q

Name three subgroups of acquired myopathies which cause intrinsic muscle disease?

A
  1. Inflammatory myopathies
  2. Endocrine myopathies
  3. Toxic myopathies
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50
Q

Name an inflammatory myopathy?

A

Polymyosytis

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51
Q

Name an endocrine myopathy?

A

Cushing syndrome, thyroid disease

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52
Q

Name a toxic myopathy?

A

Alcohol, statins

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53
Q

What is the simplest monosynaptic spinal reflex?

A

Stretch reflex

54
Q

What serves as a negative feedback that resists passive change in muscle length to maintain optimal resting length of muscle?

A

Stretch reflex

55
Q

What is the sensory receptor in stretch reflex and what is it activated by

A

Muscle spindle - activated by muscle stretch

56
Q

What does stretching the muscle spindle increase?

A

Firing in the afferent neurons

57
Q

What do afferent neurons synapse in the spinal cord with?

A

Alpha motor neurons (efferent limb of the stretch reflex) that innervate the stretched muscle

58
Q

What is the stretch reflex coordinated by?

A

Antagonist muscle

59
Q

Name the spinal segment and peripheral nerve for knee jerk?

A

L3, L4

Femoral nerve

60
Q

Name the spinal segment and peripheral nerve for ankle jerk?

A

S1, S2

Tibial nerve

61
Q

Name the spinal segment and peripheral nerve for biceps jerk?

A

C5-C6

Musculocutaneous nerve

62
Q

Name the spinal segment and peripheral nerve for Brachioradialis jerk?

A

C5-C6

Radial nerve

63
Q

Name the spinal segment and peripheral nerve for triceps jerk?

A

C6-C7

Radial nerve

64
Q

What are muscle spindles known as?

A

Intrafusal fibres

65
Q

What are ordinary muscle fibres referred to as?

A

Extrafusal fibres

66
Q

Where are muscle spindles found?

A

Within the belly of muscles and run parallel to ordinary muscle fibres

67
Q

What are the sensory nerve endings on muscle spindles known as?

A

Annulospiral fibres

68
Q

What has its own efferent (motor) nerve supply

A

Muscle spindle

69
Q

What are the efferent neurons that supply muscle spindles called?

A

Gamma motor neurons

70
Q

What adjust the level of tension in the muscle spindles to maintain their sensitivity when the muscle shortens during muscle contraction

A

Gamma-motor neurones

71
Q

What three factors cause differences between different types of skeletal muscle fibres?

A
  1. The enzymatic pathways for ATP synthesis
  2. The resistance to fatigue
  3. The activity of myosin ATPase
72
Q

What are muscle fibres with greater capacity to synthesise ATP more resistant to?

A

Fatigue

73
Q

What does activity of myosin ATPase determine?

A

Speed of contraction

74
Q

What are the three metabolic pathways that supply ATP in muscle fibre?

A
  1. Transfer of high energy phosphate from creatinine Phosphate to ADP - immediate source
  2. Oxidative phosphorylation: main source when O2 present
  3. Glycolysis: main source when O2 not present
75
Q

What activities are slow oxidative type I fibres used for?

A

Prolonged relatively low work aerobic activities

76
Q

What activities are fast oxidative (type IIa) fibres used for?

A

Prolonged relatively moderate work activities (jogging) - use both aerobic and anaerobic metabolism

77
Q

What activities are fast glycolytic (type IIx) fibres used for?

A

Short-term high intensity activities (jumping) - use anaerobic metabolism

78
Q

What susbtance is released when muscles are damaged?

A

Creatine kinase

79
Q

What are the three types of joints?

A
  1. Synovial
  2. Fibrous
  3. Cartilaginous
80
Q

What type of joint is bones united by fibrous tissue - they do not allow any movement?

A

Fibrous (synarthrosis)

81
Q

What type of joints are bones united by cartilage - they also allow limited movement?

A

Cartilaginous joint (amphiarthrosis)

82
Q

Give four examples of cartilaginous joints?

A
  1. Intervertebral discs
  2. Pubic symphsis
  3. Part of sacroiliac joints
  4. Costochondral joints
83
Q

What type of joint has bones seperated by a cavity (containing synovial fluid) and united by a fibrous capsule?

A

Synovial joint (diarthrosis)

84
Q

In a synovial joint - what is the inner aspect of fibrous capsule lined with?

A

Synovial membrane

85
Q

What - in the synovial joint - is vascular connective tissue with capillary networks and lymphatics?

A

Synovial membrane

86
Q

What does the synovial membrane contain which produces synovial fluid?

A

Synovial cells (fibroblasts)

87
Q

What is the difference between simple and compound synovial joints?

A

Simple ones have one pair of articular surfaces, compound have more than one pair of articular surfaces.

88
Q

Give an example of a simple synovial joint?

A

Metacarpalphalangeal joint

89
Q

Give an example of a compound synovial joint?

A

Elbow joint

90
Q

Joints have a role of stress distribution - what is the greatest share of loading energy taken up within?

A

Muscles and tendons crossing each other

91
Q

What three things provide joint lubrication?

A
  1. Cartilage interstitial fluid
  2. Synovium-derived hyaluronic acid (mucin) which is a polymer of disaccharides
  3. Synovium-derived lubrcin - a glycoprotein
92
Q

What part of a synovial joint supplies the chondrocytes with O2 and nutrients and removes CO2 and waste products?

A

Synovial fluid

93
Q

What is the synovial fluid continuously replinished and absorbed by?

A

The synovial membrane - not a static pool

94
Q

Why does the synovial fluid have a high viscosity?

A

Mainly due to presence of hyaluronic acid (mucin) produced by synovial cells

95
Q

What does the viscosity of synovial fluid vary with?

A

Joint movement

96
Q

What is the other consituent of synovial fluid (uric acid) derived by?

A

Dialysis of blood plasma

97
Q

Normally the synovial fluid contains few cells, what are they mainly?

A

Mononuclear leucocytes

98
Q

What happens to the synovial fluid with rapid movement?

A

Decreased viscosity and increased elasticity

99
Q

What condition causes the viscosity and elasticity to become defective?

A

Osteoarthritis

100
Q

Describe normal synovial fluid?

A

Clear and colourless

101
Q

What is the normal WBC count in synovial fluid?

A
102
Q

What does synovial fluid WBC increase in?

A

Inflammatory and septic arthritis

103
Q

What does synovial fluid turn red in?

A

Traumatic synovial tap and in haemorrhagic arthritis

104
Q

In inflammatory synovial fluid: what is the viscosity, colour, clarity, total WCC and PMN lecuocytes?

A 
Low
Straw to yellow
Translucent
2000 - 75000
often >50
105
Q

In septic synovial fluid: what is the viscosity, colour, clarity, total WCC and PMN leucocytes?

A 
Variable
Variable
Opaque
Often > 100 000
Often >75
106
Q

What are the 4 zones of articular cartilage?

A

Superficial (10-20%)
Middle (40-60%)
Deep (30%)
Calcified

107
Q

What is the ECM of articular cartilage made of?

A

Water (70%) and collagen (20%) - mainly type II contributes most to the elastic behaviour of cartilage and proteoglycans (10%)

108
Q

In articular cartilage - where os water mostly found?

A

Near articular surface

109
Q

What does cartilage water content decrease with?

A

Age

110
Q

Where is highest concentration of proteoglycan in cartilage found?

A

In middle and deep zone

111
Q

What is proteoglycan found in cartilage mainly composed of?

A

Glycosaminoglycan e.g. chondroitin suphate

112
Q

What does chondroitin in cartilage decrease with?

A

Age

113
Q

What is proteoglycan in cartilage responsible for in the role of joint?

A

Compressive properties associated with load baring

114
Q

What is the water in cartilage responsible for in role of joint?

A

Resiliency of tissue, nutrition and lubrication

115
Q

What is the collasgen in cartilage responsible for in joints?

A

Tensile stiffness and strength

116
Q

What does cartilage ECM usually constitue of the total cartilage volume?

A

> 98%

117
Q

What is the ECM of articular cartilage syntehsised, organised, degraded and maintained by?

A

Chondrocytes (

118
Q

The articular cartilage is avascular so where do cartilage ells receive nutrients and O2 from?

A

Synovial fluid

119
Q

In the cartilage ECM turnover - what has a negative effect (i.e. breakdown)?

A

Metalloproteinase proteolytic enzymes e.g. collagenase and stromelysin

120
Q

What occurs when ECM of cartilage degradation exceeds rate of synthesis?

A

Joint disease

121
Q

In cartilage ECM turnover: what does catabolic factors do?

A

Stimulate proteolytic enzymes and inhibit proteoglycan synthesis

122
Q

In cartilage ECM turnover: what two immune componenets are involved catabolically?

A

TNF-alpha

IL-1

123
Q

In cartilage ECM turnover: what does anabolic factors do?

A

Stimulate proteoglycan synthesis and counteract effects of IL-1

124
Q

In cartilage ECM turnover: what two immune components are involved anabolically?

A

TGF-beta

IGF-1

125
Q

What do increased levels of serum and synovial keratin sulphate suggest?

A

Cartilage breakdown - level increases with age and patients with osteoarthritis

126
Q

What does increased levels of type II colagen in synovial fluid suggest?

A

Cartilage breakdown - useful in evaluating cartilage erosion in osteoarthritis and rheumatoid arthritis

127
Q

Cartilage and synovial composition and function deterioate with age and repeated wear and tear giving rise to what?

A

Osteoarthritis

128
Q

What does synovial cell proliferation and inflammation cause?

A

Rheumatoid arthritis

129
Q

What does deposition of needle shaped salt crystals e.g. uric acid cause?

A

Gouty arthritis

130
Q

What does injury and inflammation to periarticular structures cause?

A

Soft tissue rheumatism e.g. injury to the tendon causes tendonitis

131
Q

What is subchondral sclerosis and cystic formation found in?

A

Osteoarthritis

132
Q

What does deposition of rhomboid shaped calcium pyrophosphate crystals cause?

A

Pseudo-gout

JL Musculoskeletal (35 decks)

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