Skeletal muscle Flashcards

1
Q

Cause of denervation atrophy

A

caused by lost connection to peripheral nerves

- unaffected motor neuron has compensatory hypertrophy

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2
Q

Type 1 muscle fiber v. type 2

A

type 1- slow (marathon runner)

Type 2- fast twitch (sprinter)

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3
Q

Cause of disuse atrophy

A

decreased contractile activity of innervated muscles causing a uniform atrophy (ex. painful lameness, fx, bone disease)

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4
Q

Cause atrophy from malnutrition/cachexia

A

caused by inability to support dietary nutrition to maintain muscle mass~ causes generalized atrophy
- cachexia is associated with neoplasia & chronic illness

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5
Q

Cause atrophy of endocrine disease

A

associated with hypothyroidism & hyperglucocorticoidism

i. Primarily selective type 2 atrophy with no compensatory type 1 hypertrophy

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6
Q

myopathic atrophy

A

muscle atrophy after primary muscle disease (ex. inflammatory muscle disease)

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7
Q

4 different patterns of myofiber necrosis

A

Focal monophasic rxn- infarct
Multifocal monophasic rxn- toxin
Focal polyphasic rxn- repeat injury/same site
Multifocal polyphasic rxn- nutritional myopathies

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8
Q

What gene is responsible for “double muscling”

A

defective myostatin gene affecting cattle, dogs & sheep

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9
Q

What is muscular dystrophy?

A

X-linked recessive disorder caused by defects in the gene encoding dystrophin.

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10
Q

hyperkalemic periodic paralysis (HYPP) disease mechanism

A

ion channel defect affecting sodium channel (muscle) that alters muscle membrane potential.

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11
Q

HYPP clinical signs

A

muscle fasciculations (spams), 3rd eyelid flashing, collapse

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12
Q

Best way to confirm HYPP

A

DNA testing

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13
Q

What breeds are predisposed to polysaccharide storage myopathy

A

draft horses, warmbloods & quarter horses

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14
Q

CS of PSM

A

recurrent exertional rhabdomyolysis–> progressive weakness

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15
Q

What gene is associated with the PSM?

A

mutated GYS1

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16
Q

Mechanism of congenital myasthenia gravis

A

inherited defect in acetylcholine end plate receptor (autosomal recessive in dogs)

17
Q

Mechanism of acquired myasthenia gravis

A

circulating antibodies to motor end plate acetylcholine receptors bind & form immune complexes at NM junction

18
Q

What is the diagnostic method for myasthenia gravis?

A

Electrodiagnostic testing, positive response to anti-cholinesterase therapy & detection of circulating anti-acetylcholine receptor antibodies.

19
Q

Malignant hyperthermia mechanism

A

defective ryanodine receptor causes a calcium release from sarcoplasmic reticulum.

20
Q

MH pathogenesis

A

prolonged myofiber contraction & muscle rigidity –> tachycardia, metabolic acidosis & hyperthermia (life threatening)

21
Q

domestic animal species affected by malignant hyperthermia

A

humans, pigs, horses & dogs

22
Q

Splayleg (condition with corresponding lesion)

A

congenital muscle condition of piglets and corresponding histopathologic lesion is myofibrillar hypoplasia.

23
Q

Compartment pathogenesis

A

increase muscle contraction causes increased muscle diameter & pressure

  • -> venous outflow collapse, continuous arterial blood supply that causes muscle metabolite accumulation and increases interstitial water
  • -> exacerbates intramuscular pressure & blood flow stops causing ischemic necrosis of muscle (worsens in 1-4 hr.)
24
Q

Compartment disease example

A

pectoral muscles in turkeys and chickens

25
Nutritional myopathy- gross changes
muscle pallor, pale streaking affecting weight bearing muscles (though, shoulder, intercostal muscles, diaphragm & tongue)
26
What type of histologic change occurs with nutritional myopathy?
polyphasic myofiber necrosis
27
What is an underlying cause of equine exertional rhabdomyolysis?
equine polysaccharide storage myopathy
28
What are potential effects of widespread rhabdomyolysis on the kidney?
myoglobininuric nephrosis & renal failure
29
Ionophore effect on muscle
acute monophasic myofiber necrosis (affect skeletal & cardiac m.), once cardiac muscle is damaged it is replaced with fibrosis
30
Senna spp. effect on muscle
acute monophasic myofiber necrosis (skeletal muscle)
31
Gossypol effect on muscle
acute segmental myofiber necrosis ( skeletal & myocardium) + hepatotoxic
32
What are different types of immune-meditated myositis in dogs?
Masticatory myositis Polymyositis Bilateral extra-ocular muscle myositis
33
How do you diagnose immune mediated myositis in dogs?
distribution of affected muscles histopathology detection of serum type 2M antibodies (masticatory myositis)
34
What are different bacterial agents of clostridial myositis?
a. Blackleg: C. chauvoei b. Malignant edema: C. speticum c. Gas gangrene: C. perfringes d. Swelled head (sheep): C. novyi
35
Gross changes observed with black leg?
i. Muscle is dark red/black, emphysematous & smell like rancid butter ii. Fibrinous/ fibrohemorrhagic pleuritis & pericarditis
36
What is the best diagnostic method for detecting black leg?
fluorescent antibody testing (hard to culture)
37
What is a benign tumor of striated myofiber?
rhabdomyoma
38
What is malignant neoplasm of myofiber?
Rhabdomyosarcoma
39
List 5 primary muscle tumors of non- muscle origin
soft tissue sarcomas, HAS, LSA, granular cell tumor & infiltrative lipoma