Muscle PP 1

Question 1

Sarcomere

Answer 1

Basic contractile unit of a myocyte (muscle fiber)

Question 2

Sarcoplasm

Answer 2

Cytoplasm of muscle cells

Question 3

Sarcolemma

Answer 3

Cell membrane of muscle cells

Question 4

Myofilaments

Answer 4

Made of actin and myosin

Question 5

Endomysium

Answer 5

Layer of loos CT with fine fibers and capillaries that enclose muscle cells

Question 6

Fascicles

Answer 6

Bundles where skeletal muscle cells organized

Question 7

Permysium

Answer 7

Layer of loose CT surrounding each fascicle

Question 8

To form a muscle, multiple fascicles are enclosed and bound together by a sheath of dense CT known as __________

Answer 8

Epimysium

Question 9

Type 1 muscle fiber (red)

Answer 9

Slow twitch, fatigue resistant
Rich in myoglobin and mitochondria

Question 10

Type 2 fibers (white)

Answer 10

Fast twitch, fatigue sensitive
Low myoglobin and mitochondria

Question 11

CS of muscle disease

Answer 11

Muscle atrophy and hypertrophy
Swelling, weakness, abnormal gait
Muscle spasm
Esophageal dysfunction

Question 12

What are the 2 main responses to injury?

Answer 12

1. Necrosis and regeneration
2. Alteration in myofiber size

Question 13

Hypoplasia

Answer 13

↓ cell number (leading to atrophy)
Loss of motor innervation during development

Question 14

Degeneration

Answer 14

Only a segment of the myocyte effected

Question 15

Necrosis

Answer 15

Entire myocyte effected

Question 16

Lesions associated with muscle disease

Answer 16

Diffuse paleness or streaks in muscle (gross)
Swollen hyalinized, fragmented sarcoplasm, loss of cross striations
+/ - mineralization of sarcoplasm

Question 17

Histopath lesions associated with muscle disease

Answer 17

Myoglobinemia and myoglobinuria
↑ serum creatine phosphokinase

Question 18

What causes degeneration and necrosis?

Answer 18

Ischemia
Bacterial toxins and associated hydrolytic enzymes
↑ intra-sarcoplasmic Ca+

Question 19

Necrosis and regeneration

Answer 19

1. Segmental hypercontraction
2. Hyaline degradation
3. Fragmentation

Question 20

Cells associated with necrosis and regeneration

Answer 20

Macrophages
Satellite cells activate and undergo mitosis (activated myoblasts)
Proliferating myoblasts for myotubes

Question 21

Influx of extracellular Ca+

Answer 21

Chalky and white
1. Dystrophic (Ca+ in dead/ dying muscle)
2. Metastatic (metabolic disorders and plants with Vit D)

Question 22

Cestrum Diurnum (plant)

Answer 22

Affects arteries, tendons and ligaments but not skeletal muscle
Glycoside yields Vit. D3

Question 23

Solanum Malacoxylon (plants)

Answer 23

Hypervitaminosis D
Tendons arteries and kidney

Question 24

Atrophy

Answer 24

↓ mass due to fewer and shorter myofilaments
Due to ↓ work load or loss of motor innervation

Question 25

Physiologic causes of atrophy

Answer 25

Disuse, cachexia, and aging

Question 26

Endocrine based atrophy

Answer 26

Most common in dogs: hypothyroidism, hyperadrenocorticism
Equine’s cushings (PPID)

Question 27

Denervation atrophy

Answer 27

Equine laryngeal hemiplegia (left recurrent laryngeal nerve)

Question 28

Hypertrophy

Answer 28

↑ mass due to sarcomeres (cell size)
Due to ↑ workload
↑ volume and weight

Question 29

Degenerative diseases of muscle

Answer 29

Trauma → ischemia
Leads to muscle damage and neuropathy
ex: downer cows

Question 30

Muscular Dystrophy

Answer 30

Inherited progressive myodegeneration and myonecrosis
Defective dystophin gene

Question 31

Malignant hyperthermia

Answer 31

Inherited defect in Ca-gating regulation → uncontrolled release of Ca from sarcoplasmic reticulum
Acute myodegeneration and myonecrosis
Triggered by stress, halothane anesthesia

Question 32

Other names for malignant hyperthermia

Answer 32

Porcine stress syndrom or Pale soft exudative pork

Question 33

CS with malignant hyperthermia

Answer 33

Normal until triggered
Severe muscle rigidity and ↑ body temperature
Muscles pale pink moist, swollen with cooked appearance
Pulmonary edema
Rapid autolysis

Question 34

Neuromuscular dysregulation

Answer 34

MG
Acquired: destroys ACh receptors on myocyte
Inherited: inadequate # of ACh receptors

Question 35

Steatosis (lipomastosis)

Answer 35

Replacement of muscle tissue by adipose tissue
Common in fattened pigs
No CS, found @ slaughter