Muscular Tissue Flashcards
Myofibrils are best described as?
Subcellular structures of contractile proteins
Identify a single sarcomere?
Distance between two Z lines
Does A band shorten when muscle contracts?
No
A muscle biopsy characteristic for Duchene muscular dystrophy would reveal?
Marked variation in muscle fibers diameter, with both large and abnormally small fibers
What is the role of protein titin in skeletal muscle?
Center the myosin filaments in the middle of the sarcomere, maintain distance between actin and myosin
Which best describes a t tubule?
In response to depolorization, activates voltage sensor proteins
Regeneration of skeletal muscle tears happens through which mechanism
Satellite cells would differentiate into myoblasts
Which structure transmits impulses for cardiac muscle contraction?
Purkinje fibers
Which protein in the troponin complex inhibits the binding of myosin to actin?
TnI
What is the connective tissue cover around a SINGLE smooth muscle cell?
Endomysium
What is the connective tissue cover around a myofibril?
Perimysium
What is the connective tissue cover around a GROUP of muscle myofibrils?
Epimysium
Role of TnT?
Binds troponin complex to tropomyosin
Role of TnC?
Calcium binding receptor, most important for contraction
What does tropomyosin cover on the actin filament?
Myosin binding sites
Can smooth muscle cells regenerate and repair?
Yes, they respond by undergoing mitosis, regularly replicating in uterus, stomach, blood vessels
What do smooth muscle cells secrete?
Connective tissue matrix
What do smooth muscle cells synthesize?
Type IV collagen, Type III, Type 1 in some areas like uterus and blood vessels
Elastin, proteoglycans, and glycoproteins
What is the arrangement of Myosin II in smooth muscle cells?
Side polar arrangement, maximizes the interaction between myosin and actin filaments
What thin filaments does smooth muscle contain?
Actin, tropomyosin, caldesmon, calponin
What does caldesmon and calponin need in order to work properly?
Calmodulin
What are caldesmon and calponin?
Actin binding proteins that block myosin binding sites
Caveolae can be found where?
In smooth muscle cell membrane, usually always with cisterna
What does caveolae invaginations do?
Regulate the release of Ca2+ from the SR
Dense bodies in smooth muscle are attached to?
Actin and desmin
Desmin attached to the dense bodies and sarcolemma does what to sarcolemma?
Throws sarcolemma in different directions when muscle is contracting
Where can mitochondria be found in smooth muscle?
Perinuclear and sub sarcolemma
What type of collagen is abundant in smooth muscle?
Type III, reticular fibers
Where can the intermediate filament vimentin be found?
Vascular smooth muscle cells
Smooth muscle cells often have a ______ appearance when muscle is contracting?
Corkscrew
Where can smooth muscle cells be found?
GI tract, blood vessels, uterus, respiratory tract
What are GAP junctions in smooth muscle called?
Nexus junction
Where can lipofuscin granules be found in an aging adult?
Juxtanuclear area
What structural subunit can be found in blood for 2 weeks after suspected myocardial infarction?
TnI
What structural subunits get release into blood after MI?
TnT and TnI
What marker can we test if we suspect a recent myocardial infarction?
TnI
In nonfatal damages to heart, what is the replacement of tissue?
Fibrous connective tissue
Why do purkinje cell cytoplasm stain poorly?
Large amounts of glycogen
Where can purkinje cells be found?
Endocardium
What do purkije fibers do?
Rapidly transmit contractil impulses to various parts of myocardium
Cardiac muscle have very large and numberous amounts of?
Mitochondria
Explain cardiac DIAD
One SR cisterna and one T tubule
T tubules are large and more numerous in?
Cardiac ventricular muscle
Where do T tubules run in cardiac muscle compared to skeletal muscle?
T tubules run on Z line in cardiac muscle, and they run at AI junction in skeletal muscle
Where can GAP junctions be found in cardiac muscle?
On the lateral component
What is the importance of GAP junctions in cardiac muscle?
Provide continuity between adjacent myocytes and allow information to pass cell to cell
What provides a cardiac cell to function as a syncytium?
GAP junctions and fascia adherens
Where can desmosomes/macula adherens be found in cardiac muscle cells?
Lateral and transverse component
What is the function of desmosomes in cardiac muscle?
Prevent cells from pulling apart after repetitive contraction
Fascia adherens serves at site where thin filaments of last sarcomere anchor to plasma membrane, therefore coincides with?
Z disc
Where can fascia adherens be found in cardiac muscle?
Transverse component, Z disk
What is the important protein in cell junctional complexes?
E-cadherins
Concentrations of what are present in between myofibrils in cardiac muscle?
Glycogen
There a dark atrial granules found in the juxtanuclear region of cardiac muscle, what polypeptide hormones are found in these granules?
ANP and BNP
What polypeptide hormone levels increase in congestive heart failure?
BNP
Can skeletal muscle be repaired if external lamina is intact?
Yes, satellite cells give rise to myoblasts, which fuse to form myotubules and eventually mature into new muscle fibers
Can skeletal muscle be repaired if external lamina is damaged?
No, fibroblasts creates scar tissue
What are satellite cells?
Stem cells that can give rise to myoblasts
What does the last sarcomere lack in a myotendinous junction?
Z line
What are tendons composed of?
Dense regular connective tissue, Type I collagen
In myotendinous junction, the actin filaments extend from A band and continue along the length of finger like projections and attach to what?
Sarcolemma
In myotendinous junction, finger like projections of ____ penetrate the muscle tissue
Type 1 collagen
Where can golgi tendon organ be found?
Tendons
What is function of golgi tendon organ?
Respond to increased tension in the muscle, relay information to CNS for coordinating fine muscle contraction
Golgi tendon organs only contain what type of nerve?
Sensory/Afferent
What is important role of efferent nerve?
To modify information from afferent nerve and send correct information to CNS
Are there more chain fibers than there are bag fibers?
Yes
Nuceli piled in a central dilation of spindle fibers is called?
Bag fiber
Nuclei closely aligned in spindle fibers is called?
Chain fiber
What are the two main intrafusal/spindle fibers?
Nuclear chain and bag fibers
What is main function of a spindle cell?
Specialized stretch receptors
What are the two capsules of spindle cells?
Internal capsule-encloses the spindle fibers
External capslue-encloses the entire cell
Fluid filled space in between capsules
What is role of AChE Acetylcholinesterase?
Breakdown ACh
The sarcolemma forms several foldings at neuromuscular junction called?
Synaptic cleft
The motor end plate has no?
Myelination
Boutons terminal ends are loacted?
In synaptic cleft
Schwann cells form a protective cover over?
Dilation of nerve
Skeletal muscle fibers are innervated by both?
Motor and sensory innervations
What is a TRIAD?
Two terminal cisternae and one T tubule
Where are TRIADs located in muscle?
AI junctions
Why are TRIADs important?
They couple the extracellular event of nerve coupling with the intracellular responses of calcium ion release
What do T tubules contain in skeletal muscle?
Voltage sensor proteins, dihydropiridine receptors
Sarcoplasmic reticulum forms a membranoius compartment of flattened?
Terminal cisternae and anastomosing channels
Importance of terminal cisternae?
Serve as reservoirs for Ca2+
Sarcoplasmic reticulum extends from?
AI junction to adjacent AI junction
What protein stores calcium in the SR?
Calsequestrin
What does TRIAD provide?
Rapid delivery and removal of Ca2+
I and H bands shorten while?
A bands stay the same length
Desmin
Attaches Z line to sarcolemma with help of linkage protein ankyrin
Crosslinks and stabilizes adjacent myofibrils
Dystrophin
Attaches actin to sarcolemma
Duchenne muscular dystrophy if gene is disrupted or absent
Why do men suffer more from Duchenne Muscular Dystrophy?
It is X linked chromosomal defect, boys only have one X chromosome
Myosin Binding Protein C
Helps myomesin protein, provides attachments on either side of M line
Myomesin
Myosin binding protein-Holds myosin at M line
Nebulin
Aids Alpha Actin in attaching actin to Z disc, maintains length of actin
Alpha Actin
Attaches actin to Z line
Titin
Maintains precise distance between actin and myosin, also centers mysoin in the middle
Molecular springs prevent excessive stretching
What does the bare zone in bipolar myosin account for?
H zone
Where can bipolar myosin filament be found?
Skeletal muscle
Myosin head has two binding sites for what?
ATP and Actin
I bands contain only?
Actin
H zone contains only?
Myosin
A bands contain?
Both myosin and actin
M line bisects H band, and Z line bisects?
I band
Each thick myosin filament is surrounded by?
6 thin actin filaments
Epimysium
CT and Type 1 collagen surrounding a group of muscle fasicles, contains large blood vessels and nerves
Perimysium
CT surrounding a group of muscle fibers, contains blood vessels
Endomysium
CT and Type 3 collagen surrounding each individual muscle fiber, contains finest vessels and nerve branches
