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
How can sarcopenia be slowed down?
With resistance exercises, some hormone treatments [e.g. Growth factors], more regulated diet (high in protein)
What are cardiac muscle fibers called?
Cardiomyocytes?
What are the characteristics of cardiac muscle?
Striated
Centrally located nucleus
Large quantities of mitochondria (aerobic muscle)
T-tubule located at z-line level
SER less developed and dudas instead of triads
Intercalated disk*
*atrial myocytes have contractile function and endocrine function
What are intercalated disk?
Complex intercellular cell junction comprising desmosome, fascia adherens and gap junction components
What endocrine function do atrial myocytes contain?
Production and secretion of natural diuretic hormones atrial natriuretic factor (ANF) and brain natriuretic factor (BNF)
Why doesn’t the heart undergo hyperplasia?
There are no satellite cells so only hypertrophy can occur (so scar tissue forms after damage)
What are the characteristics of smooth muscle?
Originates from muscle mesenchyme
No cross striations
Has contractile myofilaments and intermediate filaments
Intermediate filaments form a complex architecture with dense bodies being the equivalent of Z disc in other muscles
*caveolae
Sarcolemmmal junctions are mainly gap junctions
Smooth muscle in some organs can regenerate by mitosis if injured
In what way can smooth muscles regenerate?
Through mitosis if injured
What are caveolae?
Permanent sacolemmal invaginations (equivalent to the t-tubule of other muscles)
What is the equivalent of z disc in smooth muscle?
Dense bodies: Intermediate filaments form a complex architecture
What is indicative of cardiac muscle?
Intercalated disk
What controls smooth muscle?
ANS and hormonal control
What is the hormonal control of oxytocin?
Uterine muscle contraction during parturition
How does rigor Morris happen?
After death, Ca++ ions leak out of the SR and allow myosin head to bind to actin
Since ATP synthesis has ceased, crossbridges cannot detach from actin until proteolytic enzymes begin to digest the decomposing cells
3-4 hours after death and last 24 hours
What are the side effects of anabolic steroids?
Liver cancer
Kidney damage
Heart disease
Mood disease
Mood swings
Facial hair and voice deepening in females
Atrophy of testicles and baldness in males
