Musculoskeletal II: Muscles

Question 1

What is muscle? The three types?

Answer 1

1. It is made up of cells that can shorten or contract
2. Types:
   - Skeletal
   - Cardiac
   - Smooth

Question 2

Skeletal muscle cells (3)

Answer 2

1. Very large
2. Multinucleated
3. Numerous myofibrils composed of actin & myosin

Question 3

Mechanics of muscle contraction (2)

Answer 3

1. Relaxed muscle fibers have actin & myosin filaments that slightly overlap.
2. When stimulated to contract, cross bridges on myosin filaments slide back & forth.

Question 4

Neuromuscular junction (2)

Answer 4

1. Nerves and muscles separated by the synaptic space.
2. Synaptic vesicles - sacs at the end of a nerve fiber; contain acetylcholine.

Question 5

Initiation of muscle contraction (3)

Answer 5

1. Nerve impulse reaches the end bulb of the motor nerve fiber.
2. Acetylcholine is released into the synaptic space.
3. This neurochemical impulse triggers the release of Ca+. Ca++ diffuses into the myofibrils & starts the contraction process.

Question 6

Myopathy is a disease that affects the ___. Due to unique types of muscle, a myopathy usually affects ___ type of muscle.
Types of myopathy (4)

Answer 6

1. Muscle
2. One
   Types:
   - Inflammatory
   - Immune mediated
   - Congenital
   - Metabolic

Question 7

Inflammatory Myopathies
Etiology (2)
Clinical signs (3)

Answer 7

1. Etiology
   - Infections (esp bite wounds!)
   - Trauma
2. Clinical signs
   - Pain
   - Swelling of muscle
   - Fever

Question 8

Inflammatory Myopathies
Diagnosis (3)
Treatment (2)

Answer 8

1. Diagnosis
   - Clinical signs
   - Culture
   - Serology: toxoplasmosis & clostridia
2. Treatment
   - Tx specific disease
   - NSAIDS

Question 9

Polymyositis
What is it?
Clinical signs (4)

Answer 9

1. It is
   - Immune-mediated myopathy of skeletal muscles
2. Clinical signs
   - Mult painful muscles (“eggshell” walking)
   - Weakness, exercise intolerance
   - Fever
   - Muscle atrophy

Question 10

Polymyositis
Diagnosis (2)
Treatment (1)

Answer 10

1. Diagnosis
   - Elevated creatinine kinase
   - Muscle biopsy
2. Treatment
   - Immune suppression: Prednisone; Azathioprine

Question 11

Masticatory Myositis
Diagnosis (2)
Treatment (2)

Answer 11

1. Diagnosis
   - 2M antibody test
   - Muscle biopsy
2. Treatment
   - Immune suppression
   - Nutritional support: Liquid diets; feeding tubes

Question 12

Masticatory Myositis is an immune-mediated myositis confined to the ___ muscles of the face. Dogs are unable to open their ___. If untreated, muscle ___ and permanent “___ ___” may occur.

Answer 12

1. Masticatory
2. Mouths
3. Scarring
4. “Lock jaw”

Question 13

Feline Polymyopathy
Etiology (4)
Treatment (3)

Answer 13

1. Etiology
   - Most common cause is chronic kidney disease
   - Malnutrition
   - Insulin therapy
   - Hereditary
2. Treatment
   - Aggressive potassium supplementation
   - Tx underlying cause
   - Will completely resolve w/appropriate Tx, but life-long supplement usually needed to prevent recurrence.

Question 14

Feline Polymyopathy is profound muscle ___ and possible pain due to ___. Affects such as ___ and ___ may occur with this condition. Felines with this condition may have cervical ___.

Answer 14

1. Weakness
2. Hypokalemia (low potassium)
3. Vomiting
4. Constipation
5. Ventroflexion (cannot lift head)