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Locomotor year 2 > Muscle in health and disease > Flashcards

Muscle in health and disease Flashcards

-review basic structure and function of skeletal muscle -functions of skeletal muscle -C.T. sheaths -fibre types -DD for muscle disorders -infantile hypotonia --polymyositis/dermatomyositis -

1
Q

main component in muscle

A

water -80%

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2
Q

what is muscle a store for

A

water + glycogen + intracellular ions (ex: K+)

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3
Q

4 functions of skeletal muscle

A
  1. movement
  2. maintain posture
  3. joint stability
  4. generate heat (S.E heat production)
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4
Q

Can skeletal muscle repair itself?

A

YES - has stem cells -able to regenerate muscle fibres- last lifetime - get less efficient with age

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5
Q

What are the 2 different types of muscle fibres?

A

type 1 - slow twitch - RED
type 2- fast twitch - pale pink/WHITE

identify different muscle fibres in a muscle biopsy by ATPase staining

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6
Q

What are the different types of type 2 muscle fibres?

A 
type 2a = fastest rate of contraction - AEROBIC - WHITE
type 2b(x)= fast rate of contraction - ANAEROBIC - PINK
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7
Q

Name an example of a muscle high in type 1 fibres?

A

soleus - calf muscle- maintains posture

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8
Q

Name a muscle high in type 2a fibres

A

extraocular eye muscles

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9
Q

Name a muscle high in type 2b(x) fibres

A

GASTROCNEMIUS- calf muscle - knee flexion + plantarflexion = walking/running/posture

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10
Q

Review histology of skeletal muscle

  1. nuclei
  2. size of fibres
  3. sarcomere arrangement
  4. cell type
A
  1. peripheral nuclei
  2. muscle fibre size are all equal
  3. sarcomere aligned (striations match up from sacromere-to-sacromere)
  4. multinucleate cell- several muscle cells-fuse to 1 - 1 muscle cell runs length of muscle fibre - synchronorous + powerful contraction
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11
Q

what is a sarcomere

A

contractile unit of muscle fibre - made up from contractile filamnetous proteins - ACTIN + MYOISN

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12
Q

what is the relation of connective tissue to muscle

A

C.T is closely related to muscle - forms sheaths around muscle

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13
Q

3 places disease can affect in muscle

A
  1. muscle
  2. associated C.T sheath
  3. NMJ
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14
Q

what is epimysium

A

C.T sheath surrounding muscle (organ)

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15
Q

what is perimysium

A

C.T sheath surrounding FASICLE (group of muscle fibres)

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16
Q

what is endomysium

A

C.T sheath surrounding individual muscle fibre

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17
Q

what is a motor unit (MU)

A

MN + all the muscle fibres it innervates

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18
Q

what is the result of loss innervation of a single MN

A
  • loss of innervation to all muscle fibres supplied by the MN
  • muscle fibres ATRPOHY + SMALLER + ANGULATED
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19
Q

How can muscle fibres be re-innervation following loss of its MN innervation

A

Remaining, healthy MN sprout to innervate DE-INNERVATED fibres

  • MU enlarges
  • fibre type grouping
  • group atrophy
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20
Q

Infantile hypertonia

  1. define
  2. another name
  3. cause - 2 types
  4. histological changes
  5. prognois
A
  1. decreased muscle tone
  2. floppy baby syndrome (test-baby on back- cannot lift head)
  3. type 1 fibres larger +small type 2 fibres or vice versa - muscle unable to function properly
  4. abnormally small +round muscle fibres & groups of hypertrophic muscle fibres
  5. normal LE + QOL + only issue is inability to EXERCISE
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21
Q

why is it hard to find a definitive cause for muscular disorders

A
  • symptoms of muscle disorders are vague - muscle pain,weakness, tenderness, twitching fasiculations
  • these are symptoms with many differential diangosis
22
Q

4 possible causes for muscular problem

A
  1. neurological problem - MN de-innervation
  2. C.T disease
  3. drug exposure - statins -rhabdomyolesis -10%patients
  4. endocrine disorders - high levels thyroxine/testosterone
23
Q

Name the 3 types of inflammatory myopathies

A
  • polymyositis
  • dermatomyositis
  • inclusion body myositisi

myo = muscle
itis = inflammation
poly=many
derma=skin

24
Q

INFLAMMATORY MYOPATHIES

  • ass with which type of infection?
  • 2:1 prevelance females why?
  • onset?
  • affects which muscle
A
  • microbial
  • autoimmune disease more common in females
  • 40-60s
  • proximal muscles -quads/shoulders/biceps/hip flexors
25
Q

INFLAMMATORY MYOPATHIES

  • clinical features
  • 3 diagnostic tests
A
  • symmetrical muscle weakness + pain
    1. blood test - elevated creatine kinase levels
    2. EMG- spontaneous muscle activity - 90% cases
    3. BIOPSY
26
Q

why can serum creatine kinase be used as a marker for muscle disease?

A

CK - metabolic enzyme in muscles - ATP

  - normal cond- remains in muscle fibres
  - pathology-MUSCLE DAMAGE- CK leaks-muscle-blood
27
Q

what is the gold standard test for diagnosis of muscle disorders

A

BIOPSY

28
Q

What 4 histological changes can be seen on a biopsy in an inflammatory myopathy?

A
  1. variability in muscle fibre size
  2. central nuclei
  3. immune cell infiltration

indicate necrosis + regeneration

29
Q

what is the difference between polymyositis and dermatomyositis

A 
polymyositis = many muscles inflammed
dematomyositis= inflammation of muscles and skin
30
Q

which immune cells are seen in POLYMYOSITIS biopsy?

A

CD8+ T lymphocytes

31
Q

3 features of the rash asssociated with dermatomyositis

  1. location
  2. colour
  3. pattern
A
  1. eyelids + back
  2. helitrope (pink/purple)
  3. streaky pattern
32
Q

what complication can be found in patients with dermatomyositis, visible on X-ray

A

SUBCUTANEOUS CALCIFICATION

calcifications in muscle and skin

33
Q

what can be detected specifically in a blood test for dermatomyositis patients

A
  • ANA -autonuclear antibodies - 90% cases
  • 40% cases will have ANTI-JO1 ANTIBODY*= CYTOPLASMIC PROTEIN NOT NUCLEAR

Anti-jo1 patients - more severe disease progression -death

34
Q

What treatment is used for poly/dermatomyositis and for how long

A

CORTICOSTERIODS

  • high dose-1mg/kg per day
  • given until CK levels return to normal >2wks

(prednisolone)

35
Q

What adjunctive therapy is given for poly/dermatomyositis

A

Methotroxate + Azathioprine = steroid sparing drugs (reduce dose of steroid needed - fewer SE)

36
Q

What is inclusion body myositis?

A
  • inflammatory muscle disease
  • most apparent in legs + arms
  • symmterical muscle weakness + pain
37
Q

which INFLAMMATORY MYOPATHY is more common in MEN?

A

inclusion body myositis (ibm)

38
Q

Clinical features of inclusion body myositis (IBM)

A
  1. dysphagia

2. loss of quadricep reflex

39
Q

what features are visible on a biopsy in IBM

A

VACUOLES containing abnormally folded proteins

CK levels are only slightly elevated in blood test

40
Q

what is the most common myopathy in the elderly

A

INCLUSION BODY MYOSITIS

41
Q

Name proteins that can be found in the vacuoles of IBM

A
  • B-amyloid
  • hyperphosphorylated tau
  • apo E
42
Q

What is a muscular dystrophy (MD)?

A

PROGRESSIVE , GENETIC determined DEGENERATIVE MYOPATHIES

43
Q

What causes myopathy in MD

A

mutations in muscle protein genes

44
Q

3 groups of mutations which can cause MD and examples

A

X-linked = Duchenne + Becker MD
AR=limb girdle MD
AD=oculopharngeal MD

45
Q

DUCHENNE MD

  1. incidence
  2. onset
  3. pathology
  4. clinical features
  5. prognosis
A

1.20-30 per 100,000
2.once child starts to walk
3.DYSTROPHIN
- muscle protein absent
- reduction in sarcoglycans (glycoproteins)
-loss ability to links cell membrane - laminin
=loss of cell membrane STABILITY -muscle fibre degeneartion
4.SHOULDER + THIGH weakness ONLY
5. - wheelchair bound by age 12
-death in 20s - heart failure

only MEN

46
Q

Histological features seen in Duchenne MD biopsy

A
  1. variable muscle fibres (repeated degeneration + regeneration)
  2. endomysial fibrosis
  3. myophagocytosis
47
Q

How do patients with Duchenne MD die?

A

heart failure - dystrophin - cardiomyoctes

48
Q

What histological change occurs to muscle fibres in DMD?

A

Muscle fibers - necrosis- ADIPOSE + FIBROTIC material

49
Q 
DRUG INDUCED MYOPATHIES
Effect of:
1.corticosteroids
2.statins
3.alcohol
A
  1. type 2 atrophy
  2. rhabdomylosis -damaged skeletal muscle breaks down
  3. chronic slow progressive PROXIMAL muscle weakness
50
Q

FIBROMYALGIA

  1. define
  2. specifics
  3. comorbities
  4. gender
  5. onset
  6. autoimmune- blood test?
  7. treatment
A
  1. widespread + symmetrical muscle pain + axial skeleton
  2. > 11/18 tender points
  3. chronic fatigue syndrone + LBP + headaches + arthritis + SLEEP DISTURBANCES
  4. female =90%
  5. 30-60s
  6. ANTIPOLYMER ANITBODIES - 50% patients
  7. TCAs + SSRIs + exercise
51
Q

what is the relationship between fibromyalgia and sleep distubances

A

fibromyalgia - increases CSF level of sub P
sub P = NT - increases pain sensitivity
loss of sleep - increased sub P stores

Locomotor year 2 (11 decks)

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