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Exam 2 Skin block > Skeletal muscle > Flashcards

Skeletal muscle Flashcards

1
Q

myopathy

A

disorder of muscle

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2
Q

muscular dystrophy

A

inherited disorder

progressive muscle weakness and wasting

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3
Q

Muscle regeneration

A

satellite cells reconstitute destroyed muscle

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4
Q

fiber hypertrophy

A

response to increased load

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5
Q

myotonia

A

tonic spasm of one or more muscle; also a condition characterized by such spasms

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6
Q

hypotonia

A

deficient tone or tension

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7
Q

arthrogryposis

A

fixation joints in an extended or flexed position

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8
Q

creatine kinase (CK; CPK)

A

enzyme highly concentrated in muscle and brain

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9
Q

Gower’s sign

A

weakness of proximal muscles

uses the hands and arms to walk up from a squatting position

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10
Q

Type 1 fibers

A

action: sustained
use: endurance standing
color: red
metabolism: oxidative
glycogen: scant
lipids: abundant
mitochondria: many

z band: wide

NADH stain: dark

ATP ase Ph4.2: dark

One slow fat red ox

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11
Q

Type 2 fibers

A

action: sudden
use: short bursts speed. purposeful motion
color: white
metabolism: oxidative and anaerobic
glycogen: abundant
lipids: scant
mitochondria: few

z band: narrow

NADH stain: light

ATP ase Ph4.2: light

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12
Q

Innervating motor nuerons detrmines muscle types

A

fiber type grouping: neuron/axon drop out leads to larger motor units (muscle fibers per neuron)

grouped atrophy: loss of a motor neuron leads to atrophy of associated muscle

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13
Q

Denervation atrophy

A

disorder of motor neurons

breakdown of myosin and actin

resoption of myofibrils

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14
Q

Spinal muscular atrophy (infantile motor neuron disease; SMA): description, types, and genetics

A

progressive destruction of anterior horn cells and cranial nerve motor neurons.

Type 1: 0.4 months onset with severe hypotonia

type 2: 3 months to 2 years onset

type 3 > 2 years onset, can survive to adult

autosomal recessive: survival motor neuron 1

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15
Q

Muscular dystrophy: description and pathology

A

inherited disorders

often begin in childhood

progressive muscle weakness and wasting: may affect heart

pathology: variation in fiber size, internal nuclei, degeneration, necrosis, phagocytosis of fibers, later replaced by fibrofatty tissue

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16
Q

Duchenne MD (DMD): etiology, gene

A

Dystrophin protein defect from abnormal gene at Xp21 (deletion > frame shift or point mutation)

Huge gene (2.3 x 10^6). X linked

most common type of MD: 1/3500 male births

manifest before 5 and in wheel chair by 12

death in 20s

2/3 familial; 1/3 new mutations

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17
Q

DMD clinical

A

normal at birth

delayed walking then clumsy

weak pelvic then shoulder girlde

pseudohypertrophy of calves as fibers increase size

increased CK; later returns to normal with muscle loss

impaired cognition

death: respiratory failure, cardiac decompenstation, or lung infection

female carriers may have increased CK; risk for cardiomyopathy

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18
Q

Becerk MD

A

defect in dystrophin quality/quantitiy of protein from abnormal gene at Xp21

less common than DMD

less severe than DMD

later onset than DMD

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19
Q

Limb girdle muscular dystrophy

A

proximal muscles affected

AD, AR

begin to walk with a waddling gait because of weak hip and leg muscles

trouble getting out of chairs or climbing stairs

weakness in the shoulder make reaching over the head, holding arms, outstretched or carrying heavy objects difficult

many related to dystrophyn glycoprotein complex

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20
Q

facioscapulohumeral MD

A

facial weakness

wasting of the upper arm and shoulder msulces

the scapular bones look like wings when the arms are raised

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21
Q

Emery dreifuss MD

A

onset 10-20; triad

early on humeroperoneal weakness (proximal in the upper limbs and distal in the lower limbs)

prominent contractures, especially elbows and ankles

cardiomyopathy

22
Q

myotonic dystrophy: pathlogy and clinical features

A

myotonia (sustained involuntary contraction). Stiffness, difficulty releasing grip, can be elicited by percussion of thenar eminence

onset in childhood

other muscle features: abnormal gait from weak foot dorsiflexion, weakness of intrinsic hand and wrist extension, facial muscle atrphy and ptosis

23
Q

myotonic dystrophy: other clinical findings and genetics

A

cataracts, endocrinopathy, cardiomyopathy

autosomal dominant: dystrophilia myotonia-protein kinase. CTG repeat expain on 19q. has thousands of repeats and number of repeats expands with generations

anticipation: onset at younger age in succeeding generations

24
Q

Ion channel myopahties types

A

channelopathies mutations in ion channels

familial

myotonia and or hypotonic paralysis

malignant hyperpyrexia

25
Q

Hypotonic channelopathies: hypokalemic periodic paralysis:

A

most common 1/100,000, Ca2+ channel mutations most common,

Onset: first second decade.

Attacks of flaccid weakness provoked by carbohydrate rich meal, exercise, heat, cold, stress, medications

26
Q

Hypotonic channelopathies: other

A

hyperkalemic periodic paralysis

normokalemic periodic paralysis

27
Q

malignant hyperpyrexia: etiology and trigger

A

malignant hyperthermia

many identified genes: Ca2+, Ryanodine receptor RyR1 (RYR1)

sudden hypermetabolic state with tachypnea and general muscle contraction

triggered by anesthesia: halogen containg gases or succinylcholine

28
Q

maliganant hyperpyrexia: pathology and tx

A

release C2+ from sarcoplasmic reticulum

atp is depleted by muscle contraction

anaerobic metabolism

hyperthermia

rhabdomyolysis

hyperkalemia

renal failure

TX: dantrolene

29
Q

Congenital myopathies: age of discovery, presentation

A

defined by pathologic findings on biopsy

onset early in life

nonprogressive or slowly progressive

proximal or generalized weakness

may present as hypotonia (floppy baby) and arthrogryposis (congenital fixation of a joint in an extended or flexed position)

30
Q

Central core disease

A

autosomal dominant

hyotonia

ryanodine receptor (RYR1) gene defect

risk for malignant hyperthermia

centrally light area in type 1 fibers

pay attention to histo. Core in center.

31
Q

nemaline myopathy

A

NEM various types: autosomal dom and rec.

nonprogressive hyoptonia, weakness

delayed development in kinds

involves proximal limb muscle

subsarcolemmal spindle shaped particles from Z band (alpha actin) material

32
Q

centronuclear (myotubular) myopathy

A

various types: x linked, autosomal dominant, autosomal recessive

central nuclei usually confied to type 1 fibers

33
Q

lipid myoapthies

A

accumulate lipid in myocytes

defects in carnitine transport system

defects in mitochondrial dehydrogenase enzyme system

34
Q

mitochondrial myopathies

A

oxidative phosphorylation disease

defect may be mtDNA or nuclear DNA

many manifestations can present as young adult

ragged red fibers from aggregated mitochondria

mitochondria “parking lot” paracrystalline inclusions

35
Q

inflammatory myopathies

A

infectious: trichnella spiralis
noninfectious: dermatomyositis, polymyositis, inclusion body myositis

systemic inflammatory diseases: systemic sclerosis (scleroderma) and sarcoidosis

36
Q

Dermatomyositis: presentation. Other areas affected.

A

skin rash precedes or begins with myositis. Lilac or heliotrope discoloration of upper eyelids with periorobital edema. Scaling erythematous eruption or dusky red pathces over knuckles, elbows, knees (grotten lesions)

muscle weakness +/- myalgias. Slow and symmetrical, early proximal muscles; late distal muscles. Dysphagia in 1/3

other: lung disease, vasculitis, myocarditis

37
Q

dermatomyositis: associations. and juvenile version.

A

up to 25% have cancer. Paraneoplastic dsyndrome with breast and lung cancer

juvenile DM: in addition GI involved causing abdominal pain. GI vasculopathy leads to ulceration, hemorrhage, and perforation. Calcinosis.

38
Q

dermatomyositis vascular description and immune description

A

microvasculature attacked by antibodies and compliment creating ischemia.

Decrease in muscle capillaries.

Telangiectasisas in nail folds, eyelids, gums.

Perifascuicular atrophy: atrophy prominent at periphery of fascicles.

Inflammation in perimysial connective tissue not muscle.

CD4 T cells and B cells

39
Q

polymyositis

A

systemic inflammatory myopathy

muscle weakness +/- myalgias. early proximal muscles; late distal muscles. often dysphagia

other: lung disease, vasculitis, myocarditis.

autoantibodies against tRNA synthetases

+/- ANA positive

cytotoxic CD8 t cells in endomysium destroy muscle.

40
Q

inclusion body myositis: age, description of disease, and deposits

A

> 50 years begins insidiously: some hereditary

begins with distal muscles: begins quadriceps, wrist and finger flexors. May be asymmetric.

CD8 cytotoxic t cells

intracellular depositis of B amyloid protein, B pleated sheet fibrils, and hyperphosphorylated Tau protein.

41
Q

inclusion body myositis other types and description

A

hereditary variants

rimmed vacoles

+/- amyloid deposits

inflammation centered on myocytes

42
Q

thyrotoxic myoapthy

A

acute or chronic proximal muscle weakness

may precede signs of thyroid dysfunction

exophthalmic opthalmoplegia: protrusion of the eyballs and diplopia due to orbital edema and contracture of the ocular muscles.

43
Q

hypothyroidism myopathy

A

cramping/aching muscle; slow movements

slow reflexes

proximal weakness eg posterior neck

elevated CK

fiber atrophy

44
Q

ethanol myopathy

A

acute rhabdomyolysis after a drinking binge

painful

myoglobinuria can lead to renal failure

may be generalized or limited to a group of muscles

may be with alcoholic neuropathy

45
Q

drug induced myopathies (3 drugs)

A

steroid myopathy: proximal weakness: atrophy of predominately type 2 fibers

chloroquine myopathy: proximal weakness. Vacuoles in myocytes

Statins: 1.5% of users.

46
Q

ICU myopathy

A

profound weakness

associated with corticosteroid therapy

degraded myosin thick filaments

47
Q

myasthenia gravis: etiology and signs.

A

neuromusclar junction disease: immune mediated loss of acetylcholine receptors.

Circulation anti AchR.

decreased ACHrs

thymic hyperplasia

thymoma (an epithelial neoplasm)

48
Q

myasthenia gravis: clinical presentation

A

often begins with extraocular muscle weakness: drooping eyelids, diplopia.

may present with generalized weakness

weakness variable from minute to minute

49
Q

Myasthenia gravis: electrophysiology

A

decremental decrease in muscle response to repeated stimulus

50
Q

Myasthenia gravis: tx

A

thymectomy, anticholinesterase, predinisone, plasmapheresis

51
Q

myasthenia gravis: tenselon test

A

short acting anticholenestrase.

52
Q

lambert eaton myasthenic syndrome: etiology. associations. description.

A

neuromuscular jjunction disorder

usually paraneoplastic, most commonly from small cell carcinoma of the lung

proximal weakness and autonomic dysfunction

antibodies inhibit presynaptic calcium channel and block acetylcholine release

enhanced neurotrasmission with repetatie stimualation

Exam 2 Skin block (22 decks)

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