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Semester 3: Mind and Movement > PBL Topic 3 Case 9 > Flashcards

PBL Topic 3 Case 9 Flashcards

1
Q

What is skeletal muscle composed of?

A
  • Muscle fibres
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2
Q

What is the range of diameters of a muscle fibre?

A
  • 10-80 micrometers
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3
Q

What is the sarcolemma?

A
  • Cell membrane of the muscle fibre
  • Composed of a plasma membrane
  • And an outer polysaccharide coat containing collagen
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4
Q

What is a myofibril?

A
  • Contractile threads within muscle fibres
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5
Q

Identify two myofibrils. How many of each are located within a muscle fibre?

A
  • Myosin (1500)

- Actin (3000)

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6
Q

How are the myofibrils arranged in a muscle fibre?

A
  • They interlock

- Giving off alternate light and dark bands?

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7
Q

What is the sarcomere?

A
  • Portion of myofibril between two successive Z lines
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8
Q

What happens to the sarcomere during contraction? What is the importance of this?

A
  • Shortens 2 micrometers
  • Actin and myosin filaments overlap more
  • Creating greatest force of contraction
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9
Q

What is titin?

A
  • Molecule that maintains side-to-side relationship between actin and myosin
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10
Q

What is the sarcoplasm and what does it contain?

A
  • Space between myofibrils

- Contains large quantities of potassium ions, mitochondria and sarcoplasmic reticulum

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11
Q

Outline the structure of a myosin filament

A
  • Four light chains and two heavy chains
  • Heavy chains wrap spirally around each other into a double helix
  • Cross bridges formed by protruding arms and heads
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12
Q

Outline the structure of an actin filament

A
  • F-actin double helix protein
  • Composed of G-actin molecules which functions as active site
  • Tropomyosin wraps spirally around F-actin, covering the active sites
  • Troponin attaches to tropomyosin
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13
Q

Identify the three types of troponin

A
  • Troponin I has a strong affinity for actin
  • Troponin T has a strong affinity for tropomyosin
  • Troponin C has a strong affinity for calcium ions
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14
Q

Outline the process that allows myosin to bind with actin

A
  • Calcium binds to troponin C
  • Troponin is inhibited and moves the tropomyosin deeper into the groove between the actin strands
  • This uncovers active sites and allows myosin to bind
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15
Q

Outline the walk along theory of contraction

A
  • Myosin head binds to active site
  • Cross bridge tilts and moves the actin filament along it (power stroke)
  • Myosin head breaks away from active site and binds to another active site further along the actin filament
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16
Q

How is ATP broken down into ADP and Pi during muscle contraction?

A
  • Myosin head possesses ATPase
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17
Q

Identify two ways in which ATP influences the myosin head

A
  • Energy from breakdown of ATP allows myosin head to tilt and move actin filament along
  • Binding of ATP after power stroke causes detachment of myosin head in order to bind to another actin filament
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18
Q

Aside from action on the myosin head, identify two other roles of ATP during muscle contraction

A
  • Pumping calcium from sarcoplasm into sarcoplasmic reticulum after contraction
  • Pumping sodium and potassium across muscle fibre membrane to maintain ionic environment for propagation of action potential
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19
Q

How is phosphocreatine able to reconstitute ATP?

A
  • Breakdown of phosphocreatine donates a phosphate ion which is able to bind with ADP to form ATP
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20
Q

How is glycogen able to reconstitute ATP?

A
  • During glycolysis
  • Breakdown of glycogen to pyruvic acid and lactic acid liberates energy
  • That is used to convert ADP to ATP
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21
Q

Identify two advantages of glycogen breakdown during muscle contraction

A
  • Can occur in anaerobic conditions

- Rate of ATP formation is 2.5x that from foodstuffs

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22
Q

From which source is 95% of energy for muscle contraction derived?

A
  • Oxidative metabolism

- In which oxygen reacts with products of glycolysis to liberate ATP

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23
Q

What is the efficiency of muscle contraction and why?

A
  • 25%

- Much of the energy is lost as heat

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24
Q

How is work done calculated?

A
  • W = L x D
  • Where W is work done
  • L is load (force exerted on the muscle by a weight)
  • And D is distance of movement against the load
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25
Q

What is tension?

A
  • Force exerted on a weight by a muscle
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26
Q

What is load?

A
  • Force exerted on a muscle by a weight
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27
Q

What is meant by isometric contraction?

A
  • Contraction that does not involve lengthening or shortening of a muscle
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28
Q

What is meant by isotonic contraction?

A

-Contraction that does involve lengthening or shortening of a muscle

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29
Q

What is concentric contraction?

A
  • Isotonic contraction that involves shortening of a muscle
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30
Q

What is eccentric contraction?

A
  • Isotonic contraction that involves lengthening of a muscle
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31
Q

What is a type I fibre?

A
  • Slow oxidative fibre
  • That combines low myosin ATPase activity
  • With high oxidative energy
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32
Q

What is a type IIb fibre?

A
  • Fast glycolytic fibre
  • That combines high myosin ATPase activity
  • With high glycolytic activity
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33
Q

What is a type Ib fibre?

A
  • Fast-oxidative-glycolytic activity
  • That combines high myosin ATPase activity
  • With high oxidative capacity
  • And intermediate glycolytic activity
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34
Q

How does blood supply differ in slow and fast fibres?

A
  • More extensive in slow fibres for oxygen for oxidative phosphorlylation
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35
Q

What is myoglobin and how does the presence of myoglobin differ in slow and fast fibres

A
  • More extensive in slow fibres for storage of oxygen, giving slow fibres a red appearance
  • Less extensive in fast fibres, giving fast fibres a white appearance
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36
Q

Which type of fibre possesses a more extensive sarcoplasmic reticulum?

A
  • Fast fibres
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37
Q

Which type of fibre possesses a more glycolytic enzymes?

A
  • Fast fibres
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38
Q

Which type of fibre possesses a more mitochondria?

A
  • Slow fibres
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39
Q

What is a motor unit?

A
  • All the muscle fibres innervated by a single nerve fibre
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40
Q

The average motor unit possesses how many muscle fibre?

A
  • 80 to 100
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41
Q

What is spatial summation?

A
  • Intensity of muscle contraction can be increased by increasing the number of motor units
  • Size principle
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42
Q

What is temporal summation?

A
  • Intensity of muscle contraction can be increased by increasing the frequency of contraction
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43
Q

What is tetanisation?

A
  • As frequency increases, successive contractions fuse together, giving appearance of smooth and continuous contraction
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44
Q

What is the maximum contractile strength of a muscle?

A
  • 3-4kg per cubic centimetre
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45
Q

How is muscle tone maintained?

A
  • Low rate of nerve impulses from spinal cord
46
Q

What is muscle fatigue proportional to?

A
  • Rate of depletion of glycogen
47
Q

What is meant by coactivation of antagonist muscles?

A
  • All movements are caused by simultaneous contraction of agonist and antagonist muscles
  • Position of limb is determined by relative degrees of contraction of agonist and antagonist muscles
48
Q

Identify 4 processes that can occur in muscle remodelling

A
  • Increase in number of myofibrils (fibre hypertrophy)
  • Addition of sarcomeres to ends of muscle fibres (sarcomere hypertrophy)
  • Increase in number of muscle fibres (hyperplasia)
  • Destruction of muscle fibres (denervation atrophy)
49
Q

What is rigor mortis?

A
  • After death, muscles become rigid
  • Due to loss of ATP
  • Which causes separation of cross bridges from actin filaments
  • Lasts 24 hours
50
Q

Describe the physiological anatomy of a neuromuscular junction

A
  • Large myelinated nerve fibre branch and invaginate into muscle fibre
  • Invaginated space known as synaptic trough
  • Synaptic trough separated from nerve fibre by synaptic cleft
  • Subneural clefts located at bottom of trough
51
Q

Explain the role of Ca2+ ions on the secretion of ACh from the presynaptic nerve fibre

A
  • Binds to synaptotagmins
  • Causing a change in the SNARE complex
  • Allowing fusion of ACh vesicles with neural membrane
  • Followed by exocytosis
52
Q

Explain the effect of ACh on the postsynaptic muscle fibre membrane

A
  • Two molecules of ACh bind to ACh receptor
  • (Which is composed of two alpha, a beta, a delta and a gamma protein)
  • Allowing entry of positive sodium ions into the muscle fibre
53
Q

Explain why negative ions do not enter the postsynaptic muscle fibre

A
  • Opening possesses a negative field which repels negative ions
54
Q

What is the end plate potential and what is its value?

A
  • Local potential caused by influx of sodium ions into the end plate
  • 50 to 75 millivolts
55
Q

What are T-tubules and what is their purpose?

A
  • Dihydropyridine voltage gated calcium channel
  • That penetrates all the way through the muscle fibre
  • Allowing the action potential to penetrate deep enough to the myofibrils to cause maximum muscle contraction
56
Q

Describe the process of excitation-contraction coupling

A
  • Calcium ions enter the sarcoplasm through the T-tubules
  • Which binds to ryanodine receptors on the sarcoplasmic reticulum
  • Causing release of many more calcium ions into the sarcoplasm and into the myofibrils
  • To bind to troponin C, to relax its inhibitory grip on tropomyosin to allow myosin to bind to actin active sites
57
Q

What happens to calcium ions following muscle contraction?

A
  • Pumped out of muscle fibres by sodium calcium exchanger

- Into sarcoplasmic reticulum (regulated by phospholambin) and T-tubule extracellular fluid

58
Q

Outline the effects of training on muscle hypertrophy

A
  • Increase in number of myofibrils, mitochondrial enzymes, ATP, phosphocreatine and glycogen and triglycerides
59
Q

What is AMPK and its role?

A
  • Adenosine Monophosphate-Activated Kinase
  • Increases cellular energy
  • By inhibiting anabolic energy consuming pathways and stimulating energy producing catabolic pathways
60
Q

What is gait?

A
  • Cyclical pattern of musculoskeletal motion that carries the body forward
61
Q

Identify the two phases of gait and their relative proportions

A
  • Stance occupying 60% of the cycle

- Swing occupies 40% of the cycle

62
Q

Describe the features of antalgic gait and identify its cause

A
  • ‘Dot-dash’ movement

- Caused by pain

63
Q

Describe the feature of a gait with limb-length discrepancy

A
  • Tiptoe on shorter side

- Hip and knee flexion on longer side

64
Q

Describe the features of apraxic gait and identify its cause

A
  • Small shuffling steps (marche a petit pas)

- Caused by frontal lobe damage e.g. hydrocephalus, infarction

65
Q

Describe the features of myopathic / waddling gait and identify its cause

A
  • Patient bends pelvis forward and walks with a waddle

- Caused by muscle or hip disease

66
Q

Describe the features of diplegic / scissoring gait and identify its cause

A
  • Patient walks stiffly on the toes and has problems turning

- Bilateral upper neuron lesion causing bilateral spasticity

67
Q

Describe the features of a Parkinsonian gait and identify its cause

A
  • Stooped posture
  • Slow, shuffling gait
  • Unilateral arm swing
  • Resting tremor
  • Caused by basal ganglia dysfunction
68
Q

Describe the features of a hemiplegic gait and identify its cause

A
  • Flexed upper limbs on affected side
  • Extended lower limbs on affected side
  • With circumduction of leg
  • Unilateral upper motor neurone lesion
69
Q

Describe the features of ataxic gait and identify its cause

A
  • Broad-based gate
  • Poor tandem gait
  • Side-swinging
  • Caused by a cerebellar lesion, problem with spinocerebellum since there is overshooting of movements hence side-swinging
70
Q

Describe the features of sensory ataxia and identify its cause

A
  • Slaps the foot down on walking
  • Gait is high stepping to allow clearance of weak foot
  • Caused by damage to common fibular nerve
71
Q

What is a stress fracture?

A
  • One caused by recurrent episodes of minor trauma
  • Typically in long bones
  • Heals after rest
72
Q

What is a pathological fracture?

A
  • One caused by a disease such as osteoporosis, osteomalacia, rickets, Paget’s disease, malignant tumours
73
Q

What is a compound fracture?

A
  • One in which broken bone pierces the skin
74
Q

What is a comminuted fracture?

A
  • One in which bone is broken into more than two fragments
75
Q

Outline the process of fracture healing

A
  • Blood vessel rupture results in haematoma
  • Which is replaced by granulation tissue
  • Chondroblasts deposit hyaline over the granulation tissue to form a provisional callus
  • Osteoprogenitor cells deposit a layer of woven bone over the provisional callus forming a bony callus
  • Bony union achieved when fracture site is completely bridged by woven bone.
76
Q

Identify four causes of delayed fracture healing

A
  • Excessive movement during healing process
  • Poor intrinsic blood supply or interruption of blood supply
  • Infection in a compound fracture
  • Necrosis in a comminuted fracture
77
Q

What is the A band composed of, how does it appear?

A
  • Consists of myosin filaments as well as the actin filaments that overlap it
  • Appears dark because it is anisotropic to light
78
Q

What is the I band composed of, how does it appear?

A
  • Consists of actin filaments only on either side of the A band
  • Appears light because it is isotropic to light
79
Q

What is the Z line?

A
  • The lateral part of each actin filament is anchored to a network of interconnecting proteins known as the Z line
80
Q

What is the H zone?

A
  • Consists of myosin filaments only in the centre of the A band
  • Does not contain overlapping actin filaments
81
Q

What is the M line?

A
  • Dark band composed of proteins that link together the central region of the thick filament
82
Q

What is meant by fibre hypertrophy?

A
  • Increase in size of muscle fibre

- Due to increased number of myofibrils due to increase use

83
Q

What is meant by sarcomere hypertrophy?

A
  • Increase in size of muscle fibre
  • Due to increased stretching of a muscle
  • And increased number of sarcomeres at each end where they attach to muscles
84
Q

What is meant by fibre hyperplasia?

A
  • Increase in number of muscle fibres

- Rare

85
Q

What is meant by denervation atrophy?

A
  • As a result of impaired nerve supply to a muscle
  • Decrease in size of muscle fibre
  • And replacement with fibrous fatty tissue
  • Which continues to shorten resulting in contracture
86
Q

Identify the four stages of stance phase

A
  • Heal strike
  • Loading response
  • Midstance
  • Heal off
87
Q

Which muscles are used during heel strike? (2)

A
  • Tibialis anterior

- Gluteus maximus

88
Q

Which muscles are used during loading response? (1)

A
  • Quadriceps femoris
89
Q

Which muscles are used during midstance? (2)

A
  • Gastrocnemius

- Soleus

90
Q

Which muscles are performed during terminal stance? (2)

A
  • Gastrocnemius

- Soleus

91
Q

Identify the three stages of swing phase

A
  • Pre-swing
  • Mid-swing
  • Terminal swing
92
Q

Which muscles are used during pre-swing ? (1)

A
  • Rectus femoris
93
Q

Which muscles are used during mid-swing? (1)

A
  • Iliopsoas

- Rectus femoris

94
Q

Which muscles are used during terminal swing?

A
  • Hamstrings
  • Tibialis anterior
  • Ankle dorsiflexors
95
Q

What is a placebo?

A
  • Inert substance that causes symptom relief
96
Q

Identify three non-interactive theories of placebo

A
  • Individual trait theories e.g. personality
  • Treatment characteristics e.g. size of drug
  • Characteristics of health professional
97
Q

Identify six factors involved in the interactive theory of placebo

A
  • Experimenter bias
  • Patient’s expectations
  • Reporting error
  • Conditioning effects
  • Anxiety reduction
  • Endorphins
98
Q

Outline Cognitive Dissonance Theory with relation to placebo

A
  • For a placebo to work they must involve investment
  • For someone to invest they must see themselves as rational, in control and be able to justify their behaviour
  • If these factors align the person experiences low dissonance resulting in less distress
99
Q

How does the placebo effect relate to health beliefs?

A
  • Individual needs to believe the intervention is effective
100
Q

How does the placebo effect relate to illness cognitions?

A
  • Individual needs to believe that the illness can be overcome
101
Q

How does the placebo effect relate to health related behaviour

A
  • Individuals believe intervention promotes good health

- So take health promoting measures in other areas of their lifestyle

102
Q

How does the placebo effects relate to stress?

A
  • Reduces stress since the individual believes that they have taken control of their illness
103
Q

How does the placebo effect relate to pain reduction?

A
  • Related to opiate release or by anxiety reduction by taking intervention
104
Q

What is Shared Decision Making

A
  • Process in which clinicians and patients work together
  • To select tests, treatments, management or support packages
  • Based on both clinical evidence and the patients informed preference
105
Q

What is the importance of Shared Decision Making

A
  • Ethical imperative by professional regulatory bodies

- Patients want to be more involved than they currently are in making decisions about their own health and health care.

106
Q

What does patient driven decision making involve?

A
  • Physician presents all options
  • Physician makes no recommendation
  • Patient makes their own choice
107
Q

What does physician recommendation decision making involve?

A
  • Physician presents all options
  • Physician makes a recommendation
  • Based on patient’s values and perspective
108
Q

What is meant by equal partners decision making involve?

A
  • Physician presents all options
  • Physicians and patients work together to reach a mutual decision
  • Based on patients values and perspectives
109
Q

What is meant by informed non-dissent decision making?

A
  • Physician determines best course of action
  • Based on patients values and perspectives
  • Patient has a right to veto a decision
  • Silent is construed as tacit consent
110
Q

What is meant by physician driven decision making

A
  • Only applies to value neutral decisions
  • Care must be taken as they do not necessarily know what a patient deems as value neutral
  • Physicians should be aware of possible patient perspectives

Semester 3: Mind and Movement (21 decks)

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