Muscle Flashcards
What is a syncytium?
A multinucleated cell
What is a myofibril?
A bundle of myofilaments
What is a myofilment?
The contractile elements of muscle
What is the endomysium?
Surrounds individual muscle fibers
What is the perimysium?
Surrounds muscle fascicles
I.e. Groups of muscle fibers having the same motor innervation so that they contract together
What is the epimysium?
Fasia that surround a collection of fascicles; this is the fascia seen in the gross anatomy lab
What forms the functional unit of muscle?
Myofibrils
What give muscle it’s striated appearance?
Myofibrils
What is type I muscle?
Slow oxidative (SO) red fibers
- small fivers with lots of myoglobin and mitochondria
- slow-twitch motor units
These have less tension, less fatigue and are good for long, slow, or repetitive contractions, typically found in postural muscle
What is Type IIA muscles fibers?
Intermediate fibers
Fast oxidative glycolytic (FOG); adaptable (aerobic or anaerobic)
Large fibers wth less myoglobin
What are type IIB muscle fibers?
White fibers Glycogen rich, fast glycolytic (FG); anaerobic function Fast twitch motor units More tension and more fatigue Have more neuromuscular junctions
God for precision movements and quick, short actions
What does the sarcomere consist of?
A band I band H band M line Z disk
-This is the basic unit of muscle tissue
What does the A band contain? (Anisotropic band)
Contains actin, myosin II, titin, nebulin, and other proteins
What does the I ban contain (isotropic ban)
Contains actin, nebulin and titin
Regions lacks thick (myosin) filaments
What does the H band consist of?
Zones with no actin present are in register with each other
Change in length during contraction
Where is the M line and what does it contain?
Middle of the H-band
Rich in myomesin and C-protein
What does the Z disk consist of?
Rich in alpha-actinin and vinculin
Desmin and vimentin surround Z-discs
What do desmin and vimentin do?
Surround Z-disc DNA act as linkers to maintain Z-lines and sarcomeres in register
Dystrophin (lacking in DMD) linked them to sacolemmal transmembrane protein and CT sheath surrounding muscle fibers
What are satellite cells of muscles?
Stem cells that associated with muscle fibers
- can undergo mitosis and proliferate after fiber damage
- daughter cells will differentiate to repair muscle fiber
All muscle fibers of a motor unit that are innervated by a common axon have what in common?
Identical structural, biochemical and contractile properties
How does hypertrophy occur in muscles?
Occurs via break in Z-disks of sarcomeres
1 myofibril with 2 sarcomeres becomes 2 myofibrils with 2 sarcomeres each (this happens within a cell)
What is sarcopenia?
Type of pathology where there is a decrease in muscles mass
It is a progressive replacement of muscle with adipose tissue occurs
What may cause sacopenia? Is this reversible?
Likely cause by a combined enervation and disuse atrophy as well as the aging, damaging oxidation of specific mitochondrial enzymes
It is irreversible
In which sex does sarcopenia occur faster?
In women
