Muscle

Question 1

Name the 2 factors that primarily contribute to the degree of immobilization-induced atrophy

Answer 1

1. Degree of Immobilization (the number of joints the muscle crosses)
2. The change in muscle use relative to normal function (which is related to % slow twitch fiber area. Greater normal use & % ST, the greater the atrophy as a result of immobilization)

Question 2

What muscles will experience the greatest amount of atrophy?

Answer 2

1. Soleus (Most ST% - Most Atrophy)
2. Plantaris
3. Vastus intermedius = vastus lateralis
4. Gastrocnemius
5. Tibialis anterior = rectus femoris

Question 3

When a muscle is not being used, we see a decrease in protein synthesis rates while you see an increase in ____ rates.

Answer 3

protein degradation

Question 4

Total muscle mass =

Answer 4

synthesis rate + degradation rate

Question 5

What happens when the synthesis rate is less than the degradation rate? greater than?

Answer 5

atrophy is occurring; anabolism

Question 6

atrophy during immobilization occurs even with significant levels of electrical (EMG) activity occurring in the muscle

Answer 6

Atrophy

Question 7

What muscles are adaptations due to SC transection?

Answer 7

Flaccid paraplegia

2. flaccid spastic (3-4 wks post injury)

Question 8

Inflammatory muscular conditions caused by injury or an infectious pathogen. Will present muscle tear, inflammation, and tissue repair

Answer 8

Myositis

Question 9

loss of lower motoneuron muscle innervation

Answer 9

Denervation response of muscle

Question 10

What happens when muscle fiber “breaks”?

Answer 10

1. Damaged cell parts are removed – inflammation [Degeneration]
2. Damaged cell parts are replaced with new tissue – tissue healing [regeneration]
3. Thus, muscle fibers regenerate after injury

Question 11

What is the inflammatory process during muscle injury? What happens during this phase?

Answer 11

Degeneration; macrophages digest damaged cellular components in injured muscle fiber

Question 12

Where are satellite cells located?

Answer 12

They are trapped between the basal lamina and sarcolemma of the m fiber

Question 13

What is required for satellite cells to fuse and synthesize protein?

Answer 13

Basal lamina - if basal lamina is torn, a scar tissue will form

Question 14

What do satellite cells become when they fuse in a damaged muscle?

Answer 14

Myoblasts

Question 15

inability to contract and produce force

Answer 15

Muscle weakness

Question 16

Inability to sustain muscle action and/or force over time

Answer 16

Fatigability

Question 17

Inability of muscle to relax, can present in a prolonged spasm or contraction

Answer 17

Myotonous

Question 18

Uncoordinated or irregular contraction of individual muscle fibers that are spontaneous and can only be observed when the muscle is exposed (not seen through the skin, electrical results seen in EMG)

Answer 18

Fibrillation

Question 19

Muscle pain

Answer 19

Myalgia

Question 20

Involuntary, temporary stiffness of muscle which:

1. May follow a voluntary contraction
2. May be caused by electrical or mechanical stimulation
3. The patient has difficulty relaxing the muscle
4. Is linked to abnormalities in the sarcolemma ionic permeabilites.

Answer 20

Myotonic Dystrophy:

Most prevalent of adult muscular dystrophies; most common of all neuromuscular disorders

Question 21

When one is testing reflexes in someone with mytonic dystrophy, m’s will respond with a sustained muscle contraction. this is called

Answer 21

myotonic response

Question 22

A person with _____ will present with these facial features

1. Weakness and atrophy of facial muscles
2. Sternocleidomastoid, temporal, masseter muscular atrophy & weakness
3. Well-preserved posterior cervical muscles
4. Frontal baldness & Sagging lower jaw

Answer 22

Myotonic dystrophy

Question 23

Increase acetylcholine sensitivity on muscle membrane; Spontaneous electrical activity (EMG) of muscle at rest; caused by lower resting membrane potential; Extrajunctional ACh receptors on sarcolemma; Muscle Fibrillations occur; Muscle will not respond to Alternating Currents delivered at frequencies > 20 Hz

Answer 23

Denervation response of muscle (moves resting membrane potential from -90 to -70)

Question 24

Where are ACh receptors in a normal muscle fiber? where are they when a nerve is cut?

Answer 24

Only within motor endplate; throughout the cell (exntrajunctional ACh receptors)

Question 25

A clinical and biochemical condition resulting from disruption or damage to the integrity of the sarcolemma of skeletal muscle caused by Diseases, Trauma (severe), Toxins, or Side effects of prescribed medications, e.g. statins for cholesterol

Answer 25

Rhabdomyolysis

Question 26

What life-threatening complications may result from rhabdomyolysis?

Answer 26

1. Myoglobinuric acute renal failure
2. Hyperkalaemia
3. Cardiac arrest related to hyperkalaemia
4. Compartment syndromes

Question 27

What is an indicator that would be found in blood that is a specific indicator of skeletal muscle injury?

Answer 27

Carbonic anhydrase III

Question 28

What is contained in skeletal muscle? what normally controls the distribution of intracellular m content?

Answer 28

1. 40% - 50% of total body weight
2. Highly exposed & susceptible to mechanical trauma
3. Largest single pool of body water
4. 70% of total body potassium
5. Greatest concentration of sodium/potassium ATPase
   - Sarcolemma

Question 29

What happens when the sarcolemma is disrupted?

Answer 29

Rhabdomyolysis occurs; ECF, Ca, Na, and H2O enters muscle and causes massive swelling; Myoglobin, K, and enzymes exit muscle; causes the muscle fibers to become chronically depolarized

Question 30

What are the pathophysiology effects on the kidneys due to rhabdomyolysis?

Answer 30

1. Formation of heme casts in distal tubules causes obstruction and stasis
2. Proximal tubular necrosis
3. Renal ischemia
4. These disorders cause significant electrolyte abnormalities in the serum