Muscle Flashcards
(30 cards)
Name the 2 factors that primarily contribute to the degree of immobilization-induced atrophy
- Degree of Immobilization (the number of joints the muscle crosses)
- 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)
What muscles will experience the greatest amount of atrophy?
- Soleus (Most ST% - Most Atrophy)
- Plantaris
- Vastus intermedius = vastus lateralis
- Gastrocnemius
- Tibialis anterior = rectus femoris
When a muscle is not being used, we see a decrease in protein synthesis rates while you see an increase in ____ rates.
protein degradation
Total muscle mass =
synthesis rate + degradation rate
What happens when the synthesis rate is less than the degradation rate? greater than?
atrophy is occurring; anabolism
atrophy during immobilization occurs even with significant levels of electrical (EMG) activity occurring in the muscle
Atrophy
What muscles are adaptations due to SC transection?
Flaccid paraplegia
2. flaccid spastic (3-4 wks post injury)
Inflammatory muscular conditions caused by injury or an infectious pathogen. Will present muscle tear, inflammation, and tissue repair
Myositis
loss of lower motoneuron muscle innervation
Denervation response of muscle
What happens when muscle fiber “breaks”?
- Damaged cell parts are removed – inflammation [Degeneration]
- Damaged cell parts are replaced with new tissue – tissue healing [regeneration]
- Thus, muscle fibers regenerate after injury
What is the inflammatory process during muscle injury? What happens during this phase?
Degeneration; macrophages digest damaged cellular components in injured muscle fiber
Where are satellite cells located?
They are trapped between the basal lamina and sarcolemma of the m fiber
What is required for satellite cells to fuse and synthesize protein?
Basal lamina - if basal lamina is torn, a scar tissue will form
What do satellite cells become when they fuse in a damaged muscle?
Myoblasts
inability to contract and produce force
Muscle weakness
Inability to sustain muscle action and/or force over time
Fatigability
Inability of muscle to relax, can present in a prolonged spasm or contraction
Myotonous
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)
Fibrillation
Muscle pain
Myalgia
Involuntary, temporary stiffness of muscle which:
- May follow a voluntary contraction
- May be caused by electrical or mechanical stimulation
- The patient has difficulty relaxing the muscle
- Is linked to abnormalities in the sarcolemma ionic permeabilites.
Myotonic Dystrophy:
Most prevalent of adult muscular dystrophies; most common of all neuromuscular disorders
When one is testing reflexes in someone with mytonic dystrophy, m’s will respond with a sustained muscle contraction. this is called
myotonic response
A person with _____ will present with these facial features
- Weakness and atrophy of facial muscles
- Sternocleidomastoid, temporal, masseter muscular atrophy & weakness
- Well-preserved posterior cervical muscles
- Frontal baldness & Sagging lower jaw
Myotonic dystrophy
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
Denervation response of muscle (moves resting membrane potential from -90 to -70)
Where are ACh receptors in a normal muscle fiber? where are they when a nerve is cut?
Only within motor endplate; throughout the cell (exntrajunctional ACh receptors)
