Exam 3: Skeletal Muscle Tissue Flashcards
List the three types of muscle tissue.
- Skeletal (voluntary; striated)
- Smooth (involuntary)
- Cardiac
Skeletal Muscle Characteristics:
- Multinucleated Syncytium
- Peripheral Nuclei
- Sarcomeric Arrangement
- Each fiber innnervated via a single motor axon
- Contraction = “all-or-none”
- Contains Troponin C
Explain an overview of skeletal muscle development.
- Fibers are formed during embryonic development
- hundreds of ind. mononucleated myoblasts join end-to-end to form a myotube.
- Myotube matures into the cylindrical myocte with hundreds of nuclei
- each myocyte is about 50 to 60 micrometers in diameter. compared to 10 micrometers of a typical cell
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Skeletal Muscle
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Skeletal Muscle
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Skeltal Muscle
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Skeletal Muscle
What are some characteristics of Smooth Muscle?
- Single mononucleated cells
- No sarcomeric Arrangement
- Cells innervated via ANS
- Does not respond to “all-or-none”
- can propagate the impulse themselves
- Connected via gap junctions
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Smooth Muscle
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smooth Muscle
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smooth muscle, teased
Give cardiac cell characteristics
- Single mononucleated cells
- centrally positioned nuclei
- Sarcomeric arrangement
- Communicate via gap junctions
- inercalated discs
- cells not directly innervated
Type I Myofiber:
- Referred to as dark or red fibers
- slow sustained activity
- Utilize oxidative phosphorylation
- many mitochondria
- rich in NADH transferase, myoglobin, ATPase
Type IIA myofiber:
- Intermediate staining for oxidative enzymes
- both aerobic and anaerobic respiration for ATP production
- contract more rapidly than type I fibers
- RESISTANCE TO FATIGUE
Type IIB myofiber:
- Light Staining for oxidative enzymes
- Primarily anaerobic respiration for ATP production
- Contract more rapidly than type I or IIA fibers
- Fatigue Quickly
- White or light fibers
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Cardiac Muscle
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Cardiac Muscle
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Cardiac Muscle, Acute MI
A muscle is composed of many ________, which is a bundle of __________, which is a bundle of ________. A ________ is a linear array of __________, which is made up of filaments. The thin filaments are ______, while the thick filaments are ________.
fascicles, myofibers, myofibrils, Myofibril, sarcomers, actin, myosin
A muscle is covered by a connective tissue sheet called the __________.
Epimysium
A fascicle is surround by a connective tissue sheet called the ___________, which consist of fibroblast and type I collagen fibers.
Perimysium
A ________ is a muscle cell and is surrounded by a cell membrane call the sarcolemma.
Myofiber
The ___________ covers the muscle fiber, including the sarcolemma
Endomysium
For reference ONLY
Nothing Back here.
Just for reference
Blank
How are the filaments of the sarcomere organized?
A repeating banding pattern (viewed microscopically)
Sarcomeres are separated from each other by
transverse disks called Z-lines/disks
Each sarcomere consists of a Middle “__” band Flanked By two “__” bands
A, i
What doe the “A” bands consist of?
Thick “myosin” filaments
What is the width/length of the A band equal to?
The length of the bundle of myosin filaments
In the sarcomere actin filaments interdigitate into each end of the myosin filament bundle and are attached to the _______
Z-disks at the opposite ends
What forms the “I” bands
the portion of the actin filament not within the myosin bundle.
What does the H band consist of and where is it found?
Thick (myosin) filaments and is located in the middle of the A band
What are some hallmarks of the sliding filament theory?
- Width of the A band does not change during a contraction
- Width of the I bands become shorter during a contraction
- Width of the H Band decreases during a contraction and the H band my disappear
- Distance between the 2 successive z-disk becomes shorter
- sarcomere shortens
- Shortening of all sarcomeres within muscle fiber results in the shortening of the muscle fiber during contraction
Thick Myofilaments: Myosin
- Two identical heavy chains
- head @ each end of chain
- actin binding region
- ATP binding region
- light chain binding region
- Two pairs of light chains
- essential light chains
- Regulatory Light Chains
Thin Myofilaments: Actin
- F-actin
- polymer of G actin
- actin filament consist of 2 polymers in alpha helix
- end inserts on Z-disk
- Actin-associated molecules
- Troponin
- Tropomyosin
Troponin is a complex of three molecules what are they and what do they do?
- Troponin I:
- inhibits binding btwn actin/myosin
- Troponin C:
- binds calcium ions
- Troponin T:
- Bind to tropomyosin
Where does tropomyosin sit, and how many actin monomers does it span?
sits in the groove between two f-actin strands of an actin filament, spans 7 actin monomers
Enlargements of the SR are located next to T-tubules and are referred to as
Cisternae
What do cisternae in SR do?
Sequester calcium Ions
T-tubules are ext of the Sarcolemma that extend down into the sarcoplasm, located at the A-I junctions. What is their function?
Provide electomechanical coupling for myfiber contractions by transferring the action potential of the sarcolemma into calcium release from the cisternae
What is Titin:
- A very large protein
- extends from Z-disk to middle of H-band
- Provides myosin with elasticity
What is desmin?
- Extends from one myofibril to another and to sarcolemma
What does plectin do?
- Binds desmin filaments
What is αß-crystallin?
a heat-shock protein that protects desmin from mechanical stress
Explain the role of Dystrophin:
- a calponin, links actin filaments to transmembrane proteins of muscle cell plasma membranes
- links to the extracellular matrix, which helps maintain cell stability during muscle contraction
What does the dystroglycan comples do?
links dystrophin (intracellular) to laminin-2 (extracellular)
How does dystrophin affect pts with Duchenne’s or Becker’s musclar dystrophy respectively?
- Absent in Duchenne’s
- Abnormal in Becker’s
Describe the role of satellite cells in repair, maintenace, and regeneration of skeletal muscle tissue.
- attach to myotubes before basal lamina is laid down
- generally quiescent
- Can become mitotic in times of stress
- C-Met receptor
- HGF
- Give rise to myogenic precursor cells
- Undergo several cycles of mitosis before fusing with myofibers
Neuromuscular Spindle
TBW
